Catharina A Goossens Laan

MD Otto Visser

MD Michel W J M Wouters

MD PhD Jan-Willem W Coebergh

MD PhD Cornelis J H Van De Velde

MD, PhD Maarten C C M Hulshof

MD PhD Paul J M Kil

MD, PhDMichel Mdotto Visser

W J M Wouters

MD Mdjan-Willem W Coebergh

MD Phdcornelis J H Van De Velde

MD, PhDPaul Phdmaarten C C M Hulshof

MD J M Kil

MD Catharina A Goossens -Laan

Variation in treatment policies and outcome for bladder cancer in the Netherlands

Keywords: Bladder cancer, mortality rate, treatment, volume surgery, populationbased

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction Introduction Introduction Introduction

In the Netherlands, bladder cancer is the fifth common tumor in men, and the seventh in women. [START_REF] Netherlands | Incidence of invasive tumors, specified for sex and localisation for year of incidence (1989-2007[END_REF] While the incidence of non-invasive bladder cancer in the Netherlands has been increasing, it is decreasing for invasive bladder cancer. In recent years, the mortality rates from bladder cancer decreased among males, contrasting females.(2;3) A patient with newly diagnosed non muscle-invasive disease may be cured with local treatment only; i.e. one or multiple transurethral resections of the tumor(s)(TUR-BT) with or without subsequent bladder instillations. Cystectomy is the preferred therapy, for patients with muscle-invasive bladder cancer (MIBC) and for patients who underwent unsuccessful local treatment of non muscle-invasive bladder cancer. When a patient is not eligible for a cystectomy due to co-morbidity, or old age or patient preference, radiotherapy is the second best option. [START_REF] Batterman | Guideline Diagnostics, treatment and follow-up of the Urothelial Cell Carcinoma of the bladder[END_REF] Increasing evidence for a positive association between quality of care in cancer treatment in relation to volume and infrastructure [START_REF] Hollenbeck | Volume, Process of Care, and Operative Mortality for Cystectomy for Bladder Cancer[END_REF][START_REF] Wouters | Volume-or Outcome-Based Referral to Improve Quality of Care for Esophageal Cancer Surgery in the Netherlands[END_REF][START_REF] Van Heek | Hospital Volume and Mortality After Pancreatic Resection: a Systematic Review and an Evaluation of Intervention in the Netherlands[END_REF] led us to explore variations in staging and treatment policies and its outcome for bladder cancer in the Netherlands. 5) Quality of data is generally considered to be high and completeness was estimated to be more than 95%.(6;7)

Hospitals and regions.

Patients of all (N=97) hospitals in the Netherlands were included in this study. Hospitals were grouped into three categories, i.e. 1) 9 academic hospitals 2) non-academic hospitals with teaching facilities for urology residents 3) other hospitals (community hospitals). The influence of a radiotherapy department on the choice of treatment was also investigated. Type of primary treatment was analysed according to geographic region (subdivided according to age and stage), hospital type and annual volume (≤5, >5-10 or >10 cystectomies yearly). Variations in treatment policies, according to age and stage were assessed in the nine regions.

Data analysis.

Data analysis was done with anonymised data. Stage grouping in this study was done according to the UICC TNM classification, 6th edition.( 8) cTNM was used for the diagnosis and general treatment policies including all patients and pTNM for subset analysis of cystectomy cases. Excluded from analysis were bladder tumors without histology proven diagnosis, sarcomas, lymphomas, bladder cancer only found postmortem, incomplete registrations, and tumour recurrence (except when stage 0 progressed into stage I or higher). Local treatment is defined as one or multiple transurethral resections of the tumor often followed by bladder installations.

Only the initial treatment (within six months after diagnosis) for every new tumour was registered, thereby disregarding cystectomy for an initial non muscle-invasive tumour that progressed to muscle-invasive disease more than six months after the first diagnosis or a salvage cystectomy after radiotherapy. When the initial treatment took more than six months to complete, for example in case neo-adjuvant chemotherapy preceded the cystectomy, the whole treatment was registered.

Primary treatment was grouped according to local resection or no treatment (local treatment), cystectomy, radiotherapy or chemotherapy. A patient who underwent cystectomy and radiotherapy or chemotherapy was classified as cystectomy. A patient receiving radiotherapy as well as chemotherapy was classified as radiotherapy. Curative and palliative cystectomy or radiotherapy could not be distinguished.

A subset of patients was analyzed for the proportion of lymph node dissections according to surgical volume and the 30 and 60 day-mortality rate after cystectomy. For this category the years of analysis were restricted from 2004 until 2006 as the date of cystectomy was not available for all cases in earlier years.

Statistical methods.

Logistic regression analysis was performed to examine the influence of age at diagnosis (< 60, 60-74, ≥75 years), gender, stage, type of hospital, hospital volume, CCC-region on the odds of receiving surgery (cystectomy), radiotherapy, and on either surgery or radiotherapy. All analyses, including the logistic regression analyses, were performed in STATA, version 10. Results were considered statistically significant for p<0.05.

Results

Results Results Results

During 2001-2006, 29,206 patients (78% male) were diagnosed with primary bladder cancer. Six percent of all new patients were diagnosed in academic hospitals, 23% in non-academic hospitals with a teaching facility for urology and 71% in the other hospitals. Patient, hospital, regional and treatment characteristics are presented in Table 1.

Treatment of superficial or non muscle-invasive bladder cancer

At first diagnosis, 71% of the patients had non muscle-invasive primary bladder cancer, 73% in males and 64% in females. Seventy percent of the non muscleinvasive cancers were non-invasive papillary carcinomas (Ta or stage 0a), while 30% were cancers invading the subepithelial connective tissue only (T1 or stage I). Flat tumours (carcinoma in situ or stage Tis) represented five percent of the non-muscle invasive cancers. Initial treatment of bladder cancer in the Netherlands according to stage is shown in figure 1. The vast majority of patients with non muscle-invasive cancers received TUR-BT (with or without instillations) (Tis 94%, Ta grade 1-2 99%, Ta grade 3 97%, Ta grade unknown 96%; T1 grade 1-2 96%, T1 grade 3 90%, T1 grade unknown 91%). Cystectomy was performed in 1.5% of the patients in stage Tis, <0.5% in stage Ta and 2% in low and medium grade T1-tumours. The treatment remained unknown in 4% of patients (Tis 4%, Ta grade 1-2 1%, Ta grade 3 1%, Ta grade unknown 4%; T1 grade 1-2 1%, T1 grade 3 1%, T1 grade unknown 3%). High grade T1-tumors were diagnosed in 3,043 patients (53% of all T1 tumors). Seven percent of T1G3 tumors underwent a cystectomy, and 2% received radiotherapy. A multivariate regression analysis revealed cystectomy to be performed significantly less in older patients (≥ 75 years; OR 0.2, p =0.000) and more frequent in region 7 (OR 1.82, p < 0.0035) in stage T1G3. Figure 2 shows that the proportion of patients undergoing cystectomy for muscleinvasive cancer strongly decreased with age. In a multivariate analysis the OR of patients of 60-74 years versus <60 years was 0.49 (p= 0.000) and the OR of ≥ 75 years versus <60 was 0.06 (p= 0.000). Radiotherapy was more often administered in older patients (60-74 yr OR 2.0, p= 0.000; ≥ 75 yr OR 5.2, p= 0.000). The chance of having one of both treatments declines with increasing age (60-74 yr OR 0.65, p < 0.002; ≥ 75 yr OR 0.18, p= 0.000).

Patients were more likely to undergo a curative treatment in stage III than for stage II (OR 1.6, p= 0.000). More cystectomies were performed in comparison to radiotherapy (stage III: OR cystectomy 1.5, p= 0.000 vs. radiotherapy 0.99, p < 0.9) (Figure 3). Women more often underwent cystectomy (OR cystectomy 1.2, p < 0.016; OR radiotherapy 0.75 (p= 0.000)), contrasting radiotherapy for men.

The likelihood for receiving a specific kind of treatment is not dependent on the type of hospital where the initial diagnosis was made. The availability of a radiation department in the hospital of diagnosis did not affect the likelihood for receiving radiotherapy. However, there are strong regional preferences for specific treatments as shown for patients with stage II disease (figure 3). Among patients below 75 years of age 60 to 77% underwent cystectomy in the various regions, and 10 to 28% underwent radiotherapy. The chance of undergoing a cystectomy in stage II-III disease was higher in region 2, 3 and 6 in comparison to region 1 (OR 1.4, p < 0.005; OR 1.9, p = 0.000 and OR 1.3, p < 0.024). The chance of undergoing radiotherapy in stage II-III disease was lower in region 2, 3, 6, and 8 in comparison to region 1 (OR 0.8, p < 0.016; OR 0.6, p = 0.000, OR 0.8, p < 0.031 and OR 0.7, p < 0.035, respectively). The differences in radiotherapy mainly followed differences in the application of interstitial radiotherapy (brachytherapy): the regions with a high percentage of radiotherapy were the same as those performing brachytherapy more often (region 1 and 7). In two regions (region 4 and 9) a curative treatment was performed clearly less often (OR 0.7, p < 0.009; OR 0.6, p = 0.000) than in other regions. 2).

Cystectomy

Sixty percent of the operations were performed in community hospitals. The contribution of specialized centers was slightly increasing from 13% in 2001 to 18% in 2006. In 44 hospitals five or less cystectomies were done annually, accounting for 21% of all patients, 36 hospitals an average of 6-10 operations, together comprising 46% of all cystectomies in 2006. More than ten cystectomies annually were performed in another 13 hospitals (Figure 4). The proportion of patients being operated in these high-volume hospitals increased from 32% in 2001 to 36% in 2006.

Lymph node dissections were performed in 79% of all cystectomies (Table 3), more often in specialized centers in comparison to the community hospitals (OR 2.7; p≤0,000), and significantly more often in median and high-volume hospitals (81% and 82%) in comparison to low-volume hospitals (71%) (OR 1.47 (6-10/year) and OR 1.52 (≥ 10/year) vs. low-volume hospitals; p=0,027, and p=0,043).

The overall 30-days mortality rate after cystectomy in 2004-2006 was 3.4%. (Table 3) This rate rose with increasing age of the patient from 1.1% below the age of 60, 3.1% for 60-74 years and 7.4% for patients 75 years or older. In the high-volume centers the mortality rate was significantly lower (1.2%; OR 0.2 vs. low-volume hospitals; p=0.002). Mortality rates after 60 and 90 days were higher (all hospitals combined 5.7% and 7.7% and high volume 3.1% and 4.9%), but the relative difference in mortality rate between the high, medium and low volume hospitals remained unchanged.

Discussion

Discussion Discussion

Discussion. This paper summarizes the major variations in treatment policies in the period 2001-2006 for different regions and hospital types in the Netherlands. Remarkable regional differences in the choice of primary treatments were found. Availability of interstitial radiotherapy (brachytherapy) explained much of the variation in frequency of radiotherapy use in both stage II and III disease, with subsequent lower cystectomy rates in these regions (Figure 3). Nevertheless, in two regions curative treatment options (radiotherapy or cystectomy) were clearly used less often than in other regions, suggesting disparities in the chance of receiving optimal treatment for patients with bladder cancer.

No difference in choice of treatment was found in the three different types of hospitals (academic hospital, training hospital or community hospital). Lymph node dissection and mortality rates in cystectomy procedures differed with hospital volumes. Patients in high volume centers exhibited lower mortality rates than in low volume centers. American and European guidelines indicate that a patient with a pT1G3 tumor should initially receive BCG intravesical therapy, although cystectomy can be considered. (4;9;10). The majority (90%) of patients with the high grade T1-tumours in our study received initially local therapy only (TURBT with BCG-instillations). We may conclude that this is in accordance with the current guidelines.

Radical cystectomy is considered the 'golden standard' for stage II and III (muscleinvasive) bladder cancer, being reinforced by recent updates of European and Dutch guidelines. (4;11) In view of these guidelines the low number of cystectomies for MIBC cancer patients (36%) was remarkable. Even in MIBC patients below 75 years the number of cystectomies was low (stage II 65%; stage III 68%), but seems to increase over time. However, our data are similar to a recent Swedish population-based study. The curative intent for patients with clinical stage T2_T4 bladder cancer was 41% (by means of radiotherapy (8%) or cystectomy (33%). For patients younger than 75 years, the curative intent of total treatment arm was 62%. [START_REF] Witjes | Management of the First Recurrence of T1G3 Bladder Cancer: Does Intravesical Chemotherapy Deserve a Chance?[END_REF] In comparison to the Sweden, the Dutch percentage of cystectomy was slightly higher, moreover increasing with 8% over this study period.

Our study shows that high procedure volume for cystectomy was statistically significantly associated with lower postoperative mortality, especially related to that in hospitals with a procedural annual volume of ≤5 cystectomies, where a 30-day mortality of 6.4% was found. In the Netherlands there are 44 of these low volume hospitals and together they perform 111 cystectomies a year (21% of all patients). A third of patients (36%) underwent cystectomy in high volume hospitals, which have a significantly lower mortality (1.2%), while most patients (46%) are operated in medium volume hospitals with annually 6-10 cystectomies and a mortality rate of 3.6%.

Mounting evidence suggests that high procedure volume of complex operations is related with lower operative mortality after high-risk cancer surgeries (cystectomy, esophagectomy, pancreatectomy, etc). (13;14), but the difference might partly be affected by selective referral of relatively healthy patients of higher SES. Only one Dutch study compared post-operative mortality of patients undergoing cystectomy for low-volume hospitals with an oncologic center. [START_REF] Jahnson | A Population-Based Study of Patterns of Care for Muscle-Invasive Bladder Cancer in Sweden[END_REF] The postoperative mortality was unsignificantly lower in the oncologic center (1.8% versus 3.5%). The present national population-based study is more suggestive because of its power.

Nevertheless, our study has several limitations. Though data on age and gender were available, our study lacks information on co-morbidities and performance status of patients. Though several studies have shown that radical cystectomy is a safe option in elderly fit patients, a poor performance status of patients might jeopardize surgical treatment and lead to a choice for radiotherapy or palliative treatment only. [START_REF] Hollenbeck | Volume-Based Referral for Cancer Surgery: Informing the Debate[END_REF][START_REF] Mccabe | Defining the Minimum Hospital Case-Load to Achieve Optimum Outcomes in Radical Cystectomy[END_REF][START_REF] De Vries | Outcome of Treatment of Bladder Cancer: a Comparison Between Low-Volume Hospitals and an Oncology Centre[END_REF][START_REF] Chang | Radical Cystectomy Is Safe in Elderly Patients at High Risk[END_REF]. A study in two CCC-regions showed co-morbid conditions in elderly patients to affect the choice of treatment (submitted). There could also be the patient preference to choose for a bladder sparing approach, although there is no such differential information available within the Netherlands. Then, only the cystectomies six months after first diagnoses were taken into account, so the real cystectomy volume per hospital may be larger. Up to 30% of patients with superficial tumors involves in ≥ T1-tumors, [START_REF] Sobin | TNM Classification of Malignant Tumours[END_REF] of which an unknown percentage will undergo cystectomy. Though a re-biopsy is planned within 6 weeks after local resection for T1 tumors, and will be take place within the six months interval after first diagnosis.

In most industrialized countries, medical disciplines, insurance companies and policy makers discuss potential improvements of patient safety and quality of health care. [START_REF] Albertsen | Regionalizing urologic cancer care: appropriate health care policy?[END_REF] In the literature more and more studies advocate specific volume standards for high risk cancer operations, such as ≥ 11 cystectomies a year. (14;20;21) In the United States the Leapfrog group, a large coalition of insurance companies encourages patients to have their operation in a high volume referral center since 2000, but there have been no reports about actual overall improvement in outcome from these volume-based referral initiatives. Apparently, focusing on volume only, which is only a proxy for quality of care, is not enough for improving care-processes and outcome.

Moreover, complex surgical procedures like radical cystectomy have more dimensions than mortality and depend on more than hospital volume alone. Other factors include surgeon's competence, the hospitals infrastructure e.g. quality of critical care units and broad consultant expertise, the implementation of standard pathways and protocols. [START_REF] Froehner | Complications Following Radical Cystectomy for Bladder Cancer in the Elderly[END_REF] Most important, the surgical team should be capable to handle all postoperative complications. In addition to post-operative mortality rates, patient outcome can also be measured using complication and recurrence rates, number of resected lymph nodes, surgical margins, survival rate and last but not least by the impact on quality of life. [START_REF] Albertsen | Regionalizing urologic cancer care: appropriate health care policy?[END_REF] To provide optimal quality of care for patients with muscle-invasive bladder cancer, quality of care indicators could be used for measuring and monitoring one's own performance. [START_REF] Elting | Correlation Between Annual Volume of Cystectomy, Professional Staffing, and Outcomes: a Statewide, Population-Based Study[END_REF] The facilitating cancer registries of the Comprehensive Cancer Centers could greatly assist by independently collecting extra clinical data at regional or national scale and provide feedback to attending physicians and possible specific audits undertaken by them.

  primary bladder tumours newly diagnosed in the Netherlands between January 1, 2001 and December 31, 2006 were selected from the population-based Netherlands Cancer Registry, with complete national coverage. Dutch hospitals are served in the nine regions by the largely coordinating and facilitating Comprehensive Cancer Centers (CCC). In the hospitals, registration clerks of the CCCs extract information for the registry from the medical records, notified by the Dutch National Pathology database (PALGA). A variety of data are collected, i.e. on demographics, morphology, stage at diagnosis and primary treatment (planned in the six months following diagnosis) and vital status, date of follow-up or death. Tumor site and morphology were coded according to the International Classification of Diseases for Oncology (ICD-O).(

  Between 2001 and 2006 the total annual number of cystectomies increased 23% (from 472 to 585). Eleven percent of the cystectomies were performed in clinically non-muscle invasive disease, 77% were in clinical stage II or III (T2-T4a). Twelve percent were clinical stage IV. The proportion of clinically potentially understaged patients ranged from 44% in clinical stage I, 48% in stage II and 22% in stage III (table 2). The proportion of clinically overstaged patients ranged from 12% in clinical stage III and 21% in clinical stage IV (Table

  This paper summarizes the population-based variation in treatment policies for bladder cancer in the Netherlands in the period 2001-2006. Exploring population based cancer registries for differences in patterns of care can give insight in opportunities for improvement and could lead to a change in treatment strategies. Conflict of interest statement: C.J.H. van de Velde, president of the ESSO and M.W.J.M. Wouters are both guesteditors of this special issue of the EJSO. O. Visser and J.W. Coebergh both work at a Comprehensive Cancer Center. Acknowledgements: The authors thank the registration teams of the Comprehensive Cancer Centres for the collection of data for the Netherlands Cancer Registry and the investigators of the Netherlands Cancer Registry involved in the analyses of quality of cancer care.

Figure 2 Proportion

 2 Figure 2

Figure 3 Regional 4

 34 Figure 3

  Treatment of muscle-invasive bladder cancer Almost 8,000 patients with MIBC were diagnosed in 2001-2006 (on average 1,300 annually). A cystectomy was performed in 36% of all muscle-invasive cases. In stage II 43% underwent a cystectomy, 31% received radiotherapy, <1% chemotherapy and 26% of the patients received only local treatment or no treatment. 44% of stage III patients underwent a cystectomy, 31% received radiotherapy, 1% chemotherapy, and 25% received only local treatment or no treatment. 17% of newly diagnosed patients with stage IV underwent cystectomy, while 19% received radiotherapy and 16% with chemotherapy. 48% of the stage IV patients received no therapy or only local treatment.

	An increasing proportion of stage II patients underwent cystectomy, from 39% in
	2001 to 47% in 2006, but remaining more or less constant in stage III (39%
	cystectomies in 2001 and 38% in 2006). Utilization of radiotherapy decreased from
	34% to 27% in stage II and from 36% to 30% in stage III.

Table 1

 1 Characteristics of bladder cancer in theNetherlands, 2001Netherlands, -2006

	404
	all cases Year of diagnosis 2001 2002 2003 2004 2005 2006 Sex Males Females	Number of cases 29,206 4,473 4,591 4,740 4,992 5,154 5,256 22,727 6,479	% 15.3% 15.7% 16.2% 17.1% 17.6% 18.0% 77.8% 22.2%
	Age category < 60 60-74 75 or older Clinical TNM-stage Tis Ta I II III IV Unknown Morphological classification squamous cell carcinoma transitional cell carcinoma adenocarcinoma undifferentiated carcinoma neuro-endocrine carcinoma	5,745 12,780 10,681 973 13,582 6,267 4,505 1,126 2,349 404 343 28,369 195 107 192	19.7% 43.8% 36.6% 3.3% 46.5% 21.5% 15.4% 3.9% 8.0% 1.4% 1.2% 97.1% 0.7% 0.4% 0.7%
	Hospital of first diagnosis university hospital/oncological centre non-academic teaching hospitals other hospitals (community)	1,779 6,679 20,745	6.1% 22.9% 71.0%
	Radiotherapy facilities in the hospital No Yes	23,629 5,577	80.9% 19.1%
	Comprehensive cancer centre 1 2 3 4 5 6 7 8 9	4,020 2,351 2,188 5,292 2,764 4,436 4,169 1,827 2,156	13.8% 8.0% 7.5% 18.1% 9.5% 15.2% 14.3% 6.3% 7.4%

Table 3

 3 Relation of average annual volume of cystectomy with lymph node dissection and 30day-mortality rate in newly diagnosed patients with bladder cancer in theNetherlands, 2004Netherlands, -2006. .

	Average volume	Proportion of lymph node	30 day (60 day) mortality rate
		dissections
	<= 5 per year	71%	6.4% (8.6%)
	> 5-10 per year	81%	3.6% (6.4%)
	> 10 per year	82%	1.2% (3.1%)
	Total	79%	3.4% (5.7%)


M A G Elferink
email: m.elferink@ikno.nl

M W J M Wouters

P Krijnen
email: p.krijnen@ikw.nl

V E P P Lemmens
email: v.lemmens@ikz.nl

M L E A Jansen-Landheer

C J H Van De Velde
email: c.j.h.van_de_velde@lumc.nl

S Siesling
email: s.siesling@ikno.nl

R A E M Tollenaar
email: r.a.e.m.tollenaar@lumc.nl

Disparities in quality of care for colon cancer between hospitals in the Netherlands

Keywords: colon cancer, staging, treatment, survival, guidelines

published or not. The documents may come   L'archive ouverte pluridisciplinaire

Introduction

Ever since the Institute of Medicine reviewed variations in the quality of cancer care in their 1999 report [START_REF] Hewitt | Ensuring Quality Cancer Care[END_REF],

there is an ongoing debate on this issue, not only in the United States, but also in European countries.

Especially, the differences in surgical outcome of patients treated in high and low volume hospitals and between specialized and non-specialized providers, have been studied extensively. [START_REF] Birkmeyer | Hospital Volume and Surgical Mortality in the United States[END_REF][START_REF] Birkmeyer | Surgeon Volume and Operative Mortality in the United States[END_REF][START_REF] Chowdhury | A Systematic Review of the Impact of Volume of Surgery and Specialization on Patient Outcome[END_REF] Most of these studies focus on adverse outcomes like complications and postoperative mortality; few describe differences in the proportion of patients getting optimal treatment for their cancer.

In the Netherlands, colon cancer is one of the most frequent cancers with more than 7 500 new diagnoses in 2007. [START_REF]Comprehensive Cancer Centres[END_REF] It is also one of the most frequent causes of cancer death with more than 3 800 deaths in 2007. [6] According to the current Dutch guideline, the primary treatment for colon cancer is surgery, while adjuvant chemotherapy should be considered for patients with lymph node metastasis. Therefore, adequate lymph node evaluation is important in patients with colon cancer; [START_REF] Benson | American Society of Clinical Oncology Recommendations on Adjuvant Chemotherapy for Stage II Colon Cancer[END_REF][START_REF] Berger | Colon Cancer Survival Is Associated With Decreasing Ratio of Metastatic to Examined Lymph Nodes[END_REF][START_REF] Johnson | Increasing Negative Lymph Node Count Is Independently Associated With Improved Long-Term Survival in Stage IIIB and IIIC Colon Cancer[END_REF] 10 or more lymph nodes should be evaluated for accepting N0 status. [START_REF]Guideline colon cancer[END_REF] However, regional population-based studies in the Netherlands showed large variation on the level of lymph nodes evaluated by pathologists and in the proportion of patients receiving adjuvant chemotherapy. [11;12] Currently, colon cancer patients are treated in every hospital in the Netherlands. These patients are treated in different settings: university, teaching and non-teaching hospitals; high-and low-volume hospitals, situated in urbanized or more rural regions. It is unknown, to what extent these structural differences between hospitals lead to differences in patterns of care and outcome. A number of studies demonstrated better patient outcomes in teaching versus nonteaching hospitals. [START_REF] Chaudhry | Breast Cancer Survival by Teaching Status of the Initial Treating Hospital[END_REF][START_REF] Cheung | Impact of Teaching Facility Status and High-Volume Centers on Outcomes for Lung Cancer Resection: an Examination of 13,469 Surgical Patients[END_REF][START_REF] Holm | Influence of Hospital-and Surgeon-Related Factors on Outcome After Treatment of Rectal Cancer With or Without Preoperative Radiotherapy[END_REF] Others found lower mortality with increasing hospital or surgeon volume. [16;17] However, studies on mortality among patients with colon cancer showed conflicting results: some demonstrated an association between mortality and hospital volume or teaching status, while others did not. [START_REF] Simunovic | Influence of Hospital Characteristics on Operative Death and Survival of Patients After Major Cancer Surgery in Ontario[END_REF][START_REF] Parry | Influence of Volume of Work on the Outcome of Treatment for Patients With Colorectal Cancer[END_REF][START_REF] Harmon | Hospital Volume Can Serve As a Surrogate for Surgeon Volume for Achieving Excellent Outcomes in Colorectal Resection[END_REF][START_REF] Hannan | The Influence of Hospital and Surgeon Volume on in-Hospital Mortality for Colectomy, Gastrectomy, and Lung Lobectomy in Patients With Cancer[END_REF][START_REF] Finlayson | Hospital Volume and Operative Mortality in Cancer Surgery: a National Study[END_REF][START_REF] Dimick | Hospital Volume and Surgical Outcomes for Elderly Patients With Colorectal Cancer in the United States[END_REF][START_REF] Blomqvist | Survival After Colon Cancer 1973-1990 in Sweden. Convergence Between Catchment Areas[END_REF] Aim of this study was to describe variation in staging, treatment patterns and outcome according to region and, according to type and volume of individual hospitals among patients with colon cancer in the Netherlands.

M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

Methods

Netherlands Cancer Registry

In the Netherlands, all newly diagnosed malignancies are registered in the nationwide population-based Netherlands Cancer Registry (NCR). The automated pathological archive (PALGA) and the Haematology Departments are the main sources of notification. The National Registry of Hospital Discharge Diagnosis is an additional source, which accounts for up to 8% of new cases. [START_REF] Visser | Incidence of cancer in the Netherlands[END_REF] Data are collected from the medical records by specially trained registrars and are coded according to a nationally used manual. Information on patient characteristics, tumour characteristics, treatment, hospital of diagnosis, hospital of treatment and follow-up is recorded. For coding tumour site and morphology the International Classification of Diseases for Oncology (ICD-O) is used. [START_REF]International Classification of Diseases for Oncology[END_REF] Cancers are staged according the TNM classification. [START_REF]TNM Atlas[END_REF] Quality of the data is high [START_REF] Schouten | Quality of Cancer Registry Data: a Comparison of Data Provided by Clinicians With Those of Registration Personnel[END_REF] and completeness is estimated to be at least 95%. [START_REF] Schouten | Completeness of Cancer Registration in Limburg, The Netherlands[END_REF] Patients All patients with an invasive colon carcinoma, diagnosed in the period 2001-2006 were selected from the NCR. Diagnoses without histological confirmation, diagnoses based only on autopsy findings, patients living abroad and incomplete records were excluded from analyses. Tumour site was classified as ascendens (C18.0-C18.2), transversum and descendens (C18.3-C18.6), sigmoid (C18.7) and overlapping/unknown (C18.8-C18.9). Pathological stage was used to classify the extent of the disease. In cases where pathological stage was unknown, clinical stage was used.

CCC-regions and hospitals

The Netherlands are divided in 9 regions, each served by a Comprehensive Cancer Centre (CCC). Activities of CCCs are facilitation of consultancy services, development and implementation of guidelines, improving organisation of cancer care, coordinating palliative care and the population-based cancer registry. Each CCC serves an area covering five to twenty hospitals. All hospitals are affiliated to one centre. Within each CCCregion, treatment policies are discussed within multidisciplinary meetings which may lead to differences in oncologic care between the regions. Patients of all 97 hospitals in the Netherlands were included in the analyses.

A teaching hospital was defined as a hospital which provides medical training to residents. A distinction was made between a teaching hospital for surgery and a teaching hospital for internal medicine. All teaching hospitals for surgery were also teaching hospitals for internal medicine. University hospitals were teaching hospitals affiliated to a medical university. The one specialized oncology centre in the Netherlands was also classified as a university hospital.

Hospital volume was based on the mean number of diagnoses of colon carcinoma per year or on the mean number of colon resections for cancer per year. In the Netherlands, resections for colon cancer are in general performed in the hospital of diagnosis. Hospital volume was categorized into <50 , 50-100 and >100 diagnoses/resections per year.

For the analyses of treatment and relative survival, type of hospital was based on the hospital where the tumour was diagnosed reasoning that referral of patients for treatment in another hospital can also be

M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

considered as a good standard of care. For the analyses of postoperative mortality, type of hospital was based on the hospital where the surgery was performed.

Statistical analyses

Treatment was described as percentages per stage and age group (<75 years and ≥75 years).

Variation in lymph node evaluation and adjuvant chemotherapy

Logistic regression analysis was performed to examine the influence of age at diagnosis, gender, depth of invasion, nodal involvement, type of hospital of diagnosis, hospital volume, CCC-region and year of diagnosis on the odds of having an adequate lymph node evaluation (defined as ≥10 or more evaluated lymph nodes). Patients whose tumour was removed by polypectomy and patients with distant metastasis (M1) were excluded from this analysis.

Moreover, the influence of age at diagnosis, gender, type of hospital of diagnosis, hospital volume, CCCregion and year of diagnosis on the odds of receiving adjuvant chemotherapy in patients with stage III disease colon cancer was analyzed using logistic regression analysis. To compare the performance of the individual hospitals for these two outcome measures, funnel plots were made using 95% control limits calculated around the mean of the 20% best performing hospitals. [30;31] The proportion of resections involving 10 or more evaluated lymph nodes was adjusted for age, gender, depth of invasion (pT) and nodal involvement (pN). The proportion of resected patients receiving adjuvant chemotherapy was adjusted for age and gender. Each hospital was displayed as a scatter point presenting the adjusted rate for the outcome and the hospital volume.

Variation in postoperative mortality

Logistic regression analysis was used to investigate the odds of postoperative mortality by age at diagnosis, gender, depth of invasion, type of hospital of surgery, resection volume of hospital of surgery and CCCregion. Postoperative mortality was defined as death within 30 days after surgery. Patients with distant metastasis (M1) and acute surgery (date of surgery = date of first pathological examination) were excluded from this analysis. Postoperative mortality was analysed for tumours diagnosed in 2005 and 2006, because date of surgery was not registered in the NCR until 2005.

Variation in survival

Relative excess risks (RER) of dying according to hospital type and volume were estimated by means of multivariate relative survival analyses. Relative survival, an estimation of disease-specific survival, was calculated as the ratio of the observed rates in cancer patients to the expected rates in the general population using the Ederer method. [START_REF] Ederer | Instructions to IBM 650 Programmers in Processing Survival Computations[END_REF] Results of the multivariate relative survival analyses were stratified by pathological stage of the tumour, because interaction was found between stage and hospital type. Length of follow-up was calculated as the time from diagnosis to death or to 1 st January 2008. Only first tumours were included in the multivariate relative survival analyses.

M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

6 STATA (version 10.0) was used for the analyses. A p-value below 0.05 was considered statistically significant.

M A N U S C R I P T A C C E P T E D

Results

In the period 2001-2006 39 907 patients were newly diagnosed with colon carcinoma in the Netherlands, with an annual increase from 6 016 in 2001 to 7 360 in 2006. The male/female ratio was 1:1 and 40% of the patients was aged 75 years or older. Most frequent were stage II tumours (35%). Stage was unknown for 3% of the patients. Six percent of the patients were diagnosed in a university hospital and half of the patients were diagnosed in a hospital with 50 to 100 diagnoses per year (Table 1).

Treatment

Almost all patients with stages I-III disease underwent surgical resection. Around 10% of the stage I tumours were removed by endoscopic polypectomy. Of the patients younger than 75 years with stage III disease 76% received adjuvant chemotherapy. Among patients 75 years and older this proportion was 17%. Around 60% of patients with stage IV disease underwent surgical resection of the primary tumour. The surgery of the primary tumour was combined with chemotherapy in 39% of the patients younger than 75 years and in 10% of the patients 75 years and older. The proportion of patients with stage IV who did not receive any treatment was 15% among patients younger than 75 years and 37% among patients 75 years and older (Figure 1).

Lymph node evaluation

The proportion of patients with 10 or more evaluated lymph nodes after resection increased from 31% in Patients diagnosed in a university hospital were more likely to have an adequate lymph node evaluation (OR 2.47; 95% CI 2.19-2.78). Patients diagnosed in a hospital with more than 100 resections per year were less likely to have an adequate lymph node evaluation (OR 0.70; 95% CI 0.64-0.77). There was variation between CCC-regions in the odds of having 10 or more lymph nodes evaluated (Table 2). In the funnel plot, the adjusted proportion of patients with 10 or more evaluated lymph nodes is depicted for each hospital by mean number of colon resections per year, showing a large variation between the individual hospitals (Figure 2). The proportion of patients with an adequate lymph node evaluation ranged from more than 70% to less than 20% per hospital.

Adjuvant chemotherapy

In table 3 Being diagnosed in a hospital with a large patient volume or in a university hospital was positively related with the odds of having an adequate lymph node evaluation, and being diagnosed in a teaching hospital or in a university hospital had a negative relation with the odds of receiving adjuvant chemotherapy. Differences in relative survival were found between the various types and volumes of hospitals. In total, patients diagnosed in a university hospital or patients diagnosed in a hospital with a large volume had a better survival.

In literature, the number of studies evaluating differences in quality of care between various types of providers is overwhelming. Most studies show an inverse relationship between hospital volume and mortality, especially for high risk surgical procedures.[2;16;17] However, few studies have focused on other dimensions of quality of care besides differences in morbidity and mortality after surgery. In our study two important aspects of high leverage colon cancer treatment were investigated, lymph node evaluation and the administration of adjuvant chemotherapy. The choice for these specific process measures is supported by evidence from literature.[9;33]

Lymph node evaluation

Lymph node evaluation is crucial for staging and planning treatment in patients with colon cancer. Since adjuvant chemotherapy should be considered for patients with positive lymph nodes, inadequate lymph node examination might lead to understaging and undertreatment. [7;8] On the other hand, according to Dutch treatment guidelines, adjuvant chemotherapy should be considered for patients with stage II disease who had less than 10 evaluated lymph nodes, which could lead to overtreatment. [START_REF]Guideline colon cancer[END_REF] In our study we found that patients diagnosed in a university hospital were more likely to have more lymph nodes examined. This confirms the results of earlier studies from Canada and France. [34;35] The available resources in university hospitals to provide high quality multidisciplinary cancer care could be an explanation for this result. Other studies found a positive correlation between hospital volume and number of evaluated lymph nodes. [36;37] The current study, however, found an inverse relationship and showed that patients diagnosed in highvolume hospitals were less likely to have 10 or more lymph nodes examined. This suggests that an increased workload for pathology staff might lead to a less extensive lymph node evaluation, although a high-volume hospital not necessarily has to be served by a high-volume pathology laboratory. Furthermore, the workload per pathologist depends on the number of pathologists in a staff. Unfortunately, data on individual pathologists was not available in the NCR. However, the differences found between individual hospitals are remarkable.

Adjuvant chemotherapy

M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 10

Ever since a randomized trial in the early nineties showed that patients with stage III colon carcinoma treated with adjuvant chemotherapy had a significant survival benefit [START_REF] Moertel | Fluorouracil Plus Levamisole As Effective Adjuvant Therapy After Resection of Stage III Colon Carcinoma: a Final Report[END_REF], chemotherapy after surgery has been the standard of care for stage III patients with an adequate performance status. [START_REF]Guideline colon cancer[END_REF] However, not all patients with stage III disease receive adjuvant chemotherapy. [START_REF] Van Steenbergen | Large Age and Hospital-Dependent Variation in Administration of Adjuvant Chemotherapy for Stage III Colon Cancer in Southern Netherlands[END_REF] There are several explanations why elderly patients receive adjuvant chemotherapy less often than younger patients, such as the presence of comorbidities, unfavourable performance status or patient refusal. [START_REF] Ayanian | Use of Adjuvant Chemotherapy and Radiation Therapy for Colorectal Cancer in a Population-Based Cohort[END_REF][START_REF] Kohne | Chemotherapy in Elderly Patients With Colorectal Cancer[END_REF][START_REF] Lemmens | Adjuvant Treatment for Elderly Patients With Stage III Colon Cancer in the Southern Netherlands Is Affected by Socioeconomic Status, Gender, and Comorbidity[END_REF] Our study is hampered by the lack of information about comorbidities and performance status of the patient at time of diagnoses. Nevertheless marked differences in performance status of patients between hospitals in the Netherlands have not been reported.

University hospitals and teaching hospitals proved more restraint in the use of adjuvant chemotherapy compared to general hospitals. A French regional study showed the opposite: a lower relative risk for receiving adjuvant chemotherapy in patients treated in non-teaching hospitals compared to a single university centre. [START_REF] Bouhier | Changing Practices for Diagnosis and Treatment of Colorectal Cancer in Calvados: 1990-1999[END_REF] An American study demonstrated that patients treated by surgeons practicing in a teaching hospital were more likely to see a medical oncologist. [START_REF] Luo | The Role of the Surgeon in Whether Patients With Lymph Node-Positive Colon Cancer See a Medical Oncologist[END_REF] Our contrasting findings suggest a more severe selection of patients for administering adjuvant chemotherapy in university hospitals.

Postoperative mortality

In our study, age was an important predictor for postoperative mortality. According to a review of the Colorectal Cancer Collaborative Group, the increased proportion of elderly patients undergoing emergency surgery, together with multiple co morbidities, could contribute to this increased risk of postoperative mortality. [START_REF]Surgery for Colorectal Cancer in Elderly Patients: a Systematic Review. Colorectal Cancer Collaborative Group[END_REF] However, in our study only elective procedures were included, with a very high risk of postoperative mortality in the elderly patient group compared to the younger patient group. Elderly patients undergoing major surgery can have similar outcomes as younger patients if carefully selected. [42;43] However, the risk of obstruction or even perforation in colon cancer patients forces surgeons to perform surgery in elderly patients with an unfavourable physical status. Apparently, colon resections in elderly people are high risk procedures, in which specific experience and expertise is needed.

Nevertheless, no association between postoperative mortality and the volume or teaching status of hospitals was found in our study. This confirms the results of earlier Dutch and Canadian studies, in which no association between type or volume of hospitals and postoperative mortality was found. [18;44] For other high-risk operations, like pancreatic or esophageal resections, clear differences between low-and highvolume hospitals were demonstrated, also in the Netherlands.[2;3;45] Due to the high incidence of colon carcinoma, hospital volumes are substantially higher than the hospital volume of, for example, pancreas or esophageal cancer, which might explain our results. Nevertheless, despite the lack of an inverse relationship between hospital volume and postoperative mortality, our study identified important differences in quality of care between hospitals in the Netherlands, as shown above.

Survival

Some consider survival as the most important performance indicator for cancer treatments. Process measures, like the number of lymph nodes evaluated and the use of adjuvant chemotherapy investigated in the current study, are futile, when a relationship with direct outcome measures, like survival, is lacking.

M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 11

Survival was analyzed in the present study and significant differences between hospital types and volumes were found. Survival of patients diagnosed in university hospitals was better than in other hospitals, especially those with a high volume of colon cancer diagnoses. This finding does not parallel the restrained use of adjuvant chemotherapy in stage III patients diagnosed in these university hospitals, although it could be related to a better patient selection for adjuvant chemotherapy. Furthermore, one might speculate about a more aggressive and multidisciplinary approach in case of recurrence. Unfortunately, information on incidence and treatment of recurrences is lacking in the Netherlands Cancer Registry. The relatively low survival of patients diagnosed in low volume hospitals was reported before by a nested cohort study form the US. [START_REF] Meyerhardt | Association of Hospital Procedure Volume and Outcomes in Patients With Colon Cancer at High Risk for Recurrence[END_REF] Another American population-based study found an association between both surgeon and hospital volume and outcome, but hospital volume had a stronger effect. [START_REF] Schrag | Surgeon Volume Compared to Hospital Volume As a Predictor of Outcome Following Primary Colon Cancer Resection[END_REF] Comparing quality of care between hospitals on the basis of structural characteristics like volume and teaching status might have important disadvantages. Investigating acknowledged measures of quality of care, our study shows that variation was largest on the level of the individual hospital. Characterisations of hospitals by, for instance, volume, do not necessarily correspond with quality of care and do not reveal the differences in patterns of care that lead to poor or better outcomes. The advantage of direct measurement of the care process and its outcome, is the possibility to feed this information back to individual hospitals.

Several studies have stressed the beneficial effects of quality assurance and outcome analysis in the evaluation of the quality of cancer care.

In conclusion, we found variation in treatment and outcome of patients diagnosed with colon cancer in the Netherlands, with differences based on hospital types and volumes. However, variation in quality of care seemed mainly determined on the level of the individual hospital.

M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

  2001 to 58% in 2006, with an odds ratio of 3.29 (95% CI 3.00-3.60) in 2006 compared to 2001. Female patients were more likely to have had 10 or more lymph nodes evaluated after resection. The odds ratio decreased with older age at diagnosis. The odds of having an adequate lymph node evaluation increased by year of diagnosis, up to 3.29 (95% CI 3.00-3.60) in 2006 compared to 2001. Patients with a larger depth of invasion and with nodal involvement were more likely to have had 10 or more lymph nodes evaluated.

  population-based study, analyzing Netherlands Cancer Registry data of 39 907 patients with colon carcinoma diagnosed in the period 2001-2006, considerable variation in treatment patterns and outcome was identified. The proportion of patients receiving optimal postoperative staging with adequate lymph node evaluation and accurate treatment for their cancer increased considerably over time, but differed widely between individual hospitals.

Figure 1 :Figure 2 :Figure 3 :

 123 Figure 1: Treatment according to stage and age at diagnosis

Figure3

  Figure3

  the odds of receiving adjuvant chemotherapy in patients with stage III tumours are shown. The use internal medicine or in a university hospital had a lower odds of receiving adjuvant chemotherapy, compared to patients diagnosed in a non-teaching hospital. No significant difference in adjuvant chemotherapy administration between hospitals with different volumes was found. The administration of adjuvant chemotherapy differed between CCC-regions. However, there was also a wide variation between hospitals within the regions (data not shown). The funnel plot shows, for each hospital, the adjusted proportion of 2% of the patients without distant metastasis at diagnosis undergoing an elective resection died within 30 days after surgery. Female patients had a lower odds of dying within 30 days after resection (OR 0.74; 95% CI 0.58-0.93). The odds of dying within 30 days increased with increasing age, up to 11.61 (95% CI 6.13-21.98) for patients aged 75 years and older compared to those younger than 60 years. The odds was higher for T4-tumours compared with T1-T3 tumours (OR 1.87; 95% CI 1.37-2.56). No differences in postoperative mortality were found between hospital types, hospital volumes and CCC-regions (Table4).

	ACCEPTED MANUSCRIPT
	patients younger than 75 years with stage III disease receiving adjuvant chemotherapy by mean number of
	diagnosis per year, demonstrating some variation between the hospitals (Figure 3). The proportion of
	M patients who received adjuvant chemotherapy varied from less than 50% to more than 90% for individual hospitals. Postoperative mortality A N U S C R I P T Overall, 4.Patients diagnosed in hospitals with 50-100 diagnoses colon carcinoma per year and with more than 100
	diagnoses colon carcinoma yearly had a lower risk of dying compared to patients diagnosed in a hospital with less than 50 diagnoses colon carcinoma yearly (RER 0.90; 95% CI 0.85-0.95 and RER 0.86; 95% CI 0.80-0.93, respectively). non-teaching hospital (RER 0.70; 95% CI 0.57-0.87 and RER 0.77; 95% CI 0.69-0.86, respectively). For stage IV, patients diagnosed in hospitals with 50-100 diagnoses colon carcinoma yearly and more than 100 diagnoses colon carcinoma yearly had a better survival (RER 0.88; 95% CI 0.82-0.95 and RER 0.85; 95% CI A C C E P T E D 0.77-0.94, respectively) (Table 5).
	of adjuvant chemotherapy in patients with stage III tumours increased from 49% in 2001 to 58% in 2006, with
	an odds ratio of 1.66 (95% CI 1.40-1.97) in 2006 compared to 2001. Female patients had a lower odds of
	8

receiving adjuvant chemotherapy (OR 0.88; 95% CI 0.80-0.98). The odds of receiving adjuvant chemotherapy decreased with increasing age, with an odds ratio of 0.03 (95% CI 0.03-0.04) in patients 75 years and older compared to those younger than 60 years. Patients diagnosed in a teaching hospital for

Multivariate relative excess risks (RER) of dying

In the multivariate model for all patients with colon cancer, patients diagnosed in a university hospital had a lower risk of dying compared to patients diagnosed in a non-teaching hospital (RER 0.76; 95% CI 0.69-0.83).

For stage I, survival was worse in patients diagnosed in a university hospital (RER 1.87; 95% CI 1.02-3.42).

No differences in survival of patients with stage II disease were found between hospital types or between hospital volumes. Both among patients with stage III disease and among patients with stage IV disease, patients diagnosed in a university hospital had a lower risk of dying compared to patients diagnosed in a

Table 1 :

 1 Description of study population (N=39 907)

	N	%

Table 2 :

 2 Odds ratio of having 10 or more lymph nodes evaluated in patients with stage I-III (multivariate

	logistic regression analysis)
		OR	95% CI
	Gender
	Male	1.00	Reference
	Female	1.14*	1.08-1.20
	Age at diagnosis
	< 60 years	1.00	Reference
	60-74 years	0.74*	0.69-0.79
	≥ 75 years	0.54*	0.50-0.58
	Year of diagnosis
	2001	1.00	Reference
	2002	1.16*	1.06-1.28
	2003	1.30*	1.18-1.43
	2004	1.61*	1.47-1.77
	2005	2.57*	2.34-2.81
	2006	3.29*	3.00-3.60
	Depth of invasion
	pT1	1.00	Reference
	pT2	3.06*	2.64-3.55
	pT3	5.02*	4.38-5.76
	pT4	4.62*	3.97-5.38
	Nodal involvement
	pN0	1.00	Reference
	pN+	1.27*	1.20-1.34
	Hospital of diagnosis
	Non-teaching hospital	1.00	Reference
	Teaching hospital for surgery	1.04	0.97-1.11
	University hospital	2.47*	2.19-2.78
	Annual volume of hospital of diagnosis
	<50 resections colon carcinoma	1.00	Reference
	50-100 resections colon carcinoma	0.97	0.91-1.04
	>100 resections colon carcinoma	0.70*	0.64-0.77
	Comprehensive Cancer Centre region
	1	1.00	Reference
	2	1.22*	1.11-1.34
	3	1.32*	1.19-1.47
	4	1.38*	1.24-1.55
	5	1.19*	1.08-1.32
	6	0.92	0.84-1.01

Table 3 :

 3 Odds ratio of receiving adjuvant chemotherapy in patients with stage III disease (multivariate logistic

	regression analysis)
		OR	95% CI
	Gender
	Male	1.00	Reference
	Female	0.88*	0.80-0.98
	Age at diagnosis
	< 60 years	1.00	Reference
	60-74 years	0.40*	0.34-0.46
	≥ 75 years	0.03*	0.03-0.04
	Year of diagnosis
	2001	1.00	Reference
	2002	1.05	0.88-1.25
	2003	1.22*	1.02-1.46
	2004	1.34*	1.13-1.59
	2005	1.44*	1.21-1.71
	2006	1.66*	1.40-1.97
	Hospital of diagnosis
	Non-teaching hospital	1.00	Reference
	Teaching hospital for internal medicine	0.85*	0.73-0.98
	University hospital	0.56*	0.45-0.70
	Annual volume of hospital of diagnosis
	<50 diagnoses colon carcinoma	1.00	Reference
	50-100 diagnoses colon carcinoma	1.04	0.89-1.22
	>100 diagnoses colon carcinoma	0.91	0.74-1.11
	Comprehensive Cancer Centre region
	1	1.00	Reference
	2	0.84	0.70-1.02
	3	0.73*	0.59-0.90
	4	0.86	0.69-1.07
	5	0.76*	0.63-0.93
	6	0.98	0.82-1.18
	7	0.88	0.73-1.06
	8	1.66*	1.29-2.12
	9	0.84	0.68-1.05
	* p<0.05

Table 4 :

 4 Odds ratio of death within 30 days after resection in patients without distant metastasis (multivariate

	logistic regression analysis)
		OR	95% CI
	Gender
	Male	1.00	Reference
	Female	0.74*	0.58-0.93
	Age at diagnosis
	< 60 years	1.00	Reference
	60-74 years	2.55*	1.30-5.00
	≥ 75 years	11.61*	6.13-21.98
	Depth of invasion
	T1-T2-T3	1.00	Reference
	T4	1.87*	1.37-2.56
	Unknown	1.58	0.37-6.81
	Hospital of surgery
	Non-teaching hospital	1.00	Reference
	Teaching hospital for surgery	0.95	0.71-1.28
	University hospital	1.06	0.63-1.80
	Annual volume of hospital of surgery
	<50 resections colon carcinoma	1.00	Reference
	50-100 resections colon carcinoma	1.33	0.93-1.88
	>100 resections colon carcinoma	1.23	0.77-1.98
	Comprehensive Cancer Centre region
	1	1.00	Reference
	2	0.69	0.44-1.08
	3	0.84	0.51-1.38
	4	0.95	0.58-1.57
	5	0.95	0.61-1.47
	6	0.83	0.54-1.27
	7	1.07	0.71-1.63
	8	0.61	0.32-1.16
	9	0.83	0.50-1.38
	* p <0.05

Table 5 :

 5 Relative excess risks (RER) of dying for patients with colon cancer diagnosed in the period 2001-2006, according to stage (multivariate relative Adjusted for gender, age at diagnosis, grade, year of diagnosis, tumour location, stage, surgery, chemotherapy and CCC-region 2 Adjusted for gender, age at diagnosis, grade, year of diagnosis, tumour location, depth of invasion, surgery and CCC-region 3 Adjusted for gender, age at diagnosis, grade, year of diagnosis, tumour location, depth of invasion, surgery, chemotherapy, number of positive nodes and CCC-region 4 Adjusted for gender, age at diagnosis, grade, year of diagnosis, tumour location, depth of invasion, surgery, chemotherapy and CCC-region

	survival analysis)
			Total 1		Stage I 2		Stage II 2		Stage III	3		Stage IV 4
		RER	95 % CI	RER 95% CI	RER 95% CI	RER 95% CI	RER 95% CI
	Type of hospital of diagnosis
	Non-teaching hospital	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	Teaching hospital surgery	1.03	0.98-1.09	1.11	0.70-1.76	1.14	0.99-1.31	0.96	0.86-1.07	1.05	0.98-1.12
	University hospital	0.76* 0.69-0.83	1.87* 1.02-3.42	0.74	0.54-1.00	0.70* 0.57-0.87	0.77* 0.69-0.86
	Annual volume of hospital of
	diagnosis
	<50 diagnoses colon carcinoma	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	50-100 diagnoses colon carcinoma 0.90* 0.85-0.95	0.92	0.56-1.51	0.98	0.83-1.16	0.90	0.80-1.02	0.88* 0.82-0.95
	>100 diagnoses colon carcinoma	0.86* 0.80-0.93	0.84	0.44-1.61	0.87	0.70-1.07	0.88	0.75-1.03	0.85* 0.77-0.94
	1

* p<0.05

Acknowledgements

The authors would like to thank the Netherlands Cancer Registry for providing data.

M A N U S C R I P T A C C E P T E D

Conflict of interest statement

None declared.


MD Pertti Aro
email: pertti.aro@fimnet.fi

Jukka Ronkainen

Tom Storskrubb

Michael Vieth

Lars Engstrand

Sven-Erik Johansson

Elisabeth Bolling-Sternevald

Gunilla Bolinder

Kjell Alving

Nicholas J Talley

Sven- Erik Johansson

Lars Agréus

Use of tobacco products and gastrointestinal morbidity: an endoscopic population-based study (the Kalixanda study)

Keywords: Dyspepsia, Esophagitis, Gastroesophageal reflux symptom, Peptic ulcer disease, Smoking, Snus

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Smokeless tobacco or moist snuff, snus in this study, is widely used in Sweden (900,000 users, 21% of males and 4% of females, while 13% of males and 17% of females smoke cigarettes) [START_REF]Minskat bruk av tobak -var står vi i dag. Statistik Oktober[END_REF] and also in other Nordic countries. There is a widespread use in India and the marketing is intense, while USA is the biggest market of snus in the world with approximately 12 million users [START_REF] Bolinder | Cardiovascular Mortality and Risk Factors[END_REF]3]. Results of a national US survey show that nearly 9% of male and 0.4% of the female college students used snus [START_REF] Rigotti | US college students' use of tobacco products: results of a national survey[END_REF]. In Sweden marketing efforts have resulted in higher use among young males and females have tripled their use over eight years [START_REF]Minskat bruk av tobak -var står vi i dag. Statistik Oktober[END_REF]. Swedish snus products are predominantly finely ground moistened tobacco with an alkaline pH between 7.9 and 8.6 [START_REF] Andersson | The influence of pH and nicotine concentration in oral moist snuff on mucosal changes and salivary pH in Swedish snuff users[END_REF]. A pinch of approximately 1-2 g is placed under the upper lip, and some nicotine is absorbed through the buccal mucosa, while some is swallowed together with the saliva [START_REF] Bolinder | Cardiovascular Mortality and Risk Factors[END_REF].

Epidemiological and experimental studies have shown that smoking leads to harmful effects on the gastric mucosa [START_REF] Kikendall | Effect of cigarette smoking on gastrointestinal physiology and non-neoplastic digestive disease[END_REF][START_REF] Endoh | Effects of smoking and nicotine on the gastric mucosa: a review of clinical and experimental evidence[END_REF][START_REF] Kurata | Meta-analysis of risk factors for peptic ulcer. Nonsteroidal antiinflammatory drugs, Helicobacter pylori, and smoking[END_REF][START_REF] Wu | The pharmacological actions of nicotine on the gastrointestinal tract[END_REF]. The mechanisms, however, are unclear and the effects might be mediated by inhaled nicotine, as well as by other chemical contents of tobacco. Many studies provide conflicting results but the overall evidence supports the hypothesis that nicotine per se is harmful to the gastric mucosa [START_REF] Endoh | Effects of smoking and nicotine on the gastric mucosa: a review of clinical and experimental evidence[END_REF][START_REF] Wu | The pharmacological actions of nicotine on the gastrointestinal tract[END_REF].

There is little knowledge regarding the relationship between gastrointestinal symptoms and snus. The nicotine intake is usually higher than in smokers, and a great deal of tobacco juice contaminated saliva is swallowed during use. In a Swedish cross-sectional study of symptoms in 130,000 construction workers, smokers reported "ulcer-like" dyspepsia three times as often as the non tobacco users, while snus users reported significantly fewer symptoms than both smokers and non tobacco users [START_REF] Bolinder | Use of smokeless tobacco: blood pressure elevation and other health hazards found in a large-scale population survey[END_REF].

It has been shown both in studies on patients and in population-based studies that smoking is a risk factor for peptic ulcer disease (PUD) [START_REF] Kurata | Meta-analysis of risk factors for peptic ulcer. Nonsteroidal antiinflammatory drugs, Helicobacter pylori, and smoking[END_REF][START_REF] Aro | Peptic ulcer disease in a general adult population. The Kalixanda study: A random population-based study[END_REF], but there are no data concerning snus on this issue. Data from the US show that cigarette smokers have a markedly increased risk for gastric cancer and that use of more than one tobacco product increases the risk in men [START_REF] Chao | Cigarette smoking, use of other tobacco products and stomach cancer mortality in US adults: The Cancer Prevention Study II[END_REF].

Male users of smokeless or chewing tobacco have also been shown in US prospective studies to have higher death rates from all causes compared with non-users (CPS-I and II studies) and also higher death rates from cancer of the gastrointestinal tract overall (CPS-I study), but separate data on the upper gastrointestinal tract were not shown [START_REF] Henley | Two large prospective studies of mortality among men who use snuff or chewing tobacco (United States)[END_REF].

Although there is extensive exposure to swallowed tobacco juice contaminated saliva, and high serum levels of nicotine and nitrites, there have been no studies in terms of oesophageal or gastric histology or Helicobacter pylori infection in snus users.

The aim of the study was to investigate whether smoking cigarettes and snus use are associated with gastrointestinal symptomatology, macroscopic findings on endoscopy or histological signs of inflammation or cancer risk markers in the esophagus or stomach, including the prevalence of Helicobacter pylori.

MATERIALS AND METHODS

Setting

The Kalixanda study setting consisted of two neighbouring communities in Northern Sweden (Kalix and Haparanda) with 28,988 inhabitants (December 1998). The distribution of age and sex was similar to the national average in Sweden in both communities; although proportion of unemployment, income, and the proportion with a higher education were slightly lower [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF].

Participants

By using the computerized national population register, covering all citizens in the two communities by date of birth order, a representative stratified sample was generated. Every seventh adult (n=3,000) from the target population (18-80 years of age, n=21,610 in September 1998) was drawn. The sampled subjects were given an identification number (1-3,000) in a random order [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF].

Study design and logistics

The original study population (n=3,000) was invited by mail to take part. The invitation included information of the study design and of the aims of the study and a validated questionnaire, the Abdominal Symptom Questionnaire (ASQ) to be returned by mail [START_REF] Agréus | Reproducibility and validity of a postal questionnaire. The abdominal symptom study[END_REF]. Up to two remainders were sent when necessary; 140 subjects were unavailable at the time for invitation, thus 2,860 of the original study population were eligible for inclusion [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF]. The overall response rate was 74.2% (n=2,122) of the eligible study population.

The original study population was divided into five groups according to their given identification number, 1-600, 601-1,200 and so forth, the first subset of study subjects was approached with the mailed ASQ in November 1998 and the study was completed in June 2001 [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF]. In order to complete 1,001 esophagogastroduodenoscopies (EGDs), 1,563 responders to the ASQ had to be approached of whom 364 declined, 74 had moved or could not be reached and 124 were excluded according to the study protocol. Thus the overall response rate for those eligible for the EGD was 73.3% [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF]. The exclusion criteria were the presence of serious physical or mental disorder, alcoholism, previous upper gastrointestinal surgery and pregnancy [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF]. The biopsies for Helicobacter pylori culture and concomitant histology were available from 1,000 subjects. At the visit for the EGD, the participants filled in a more comprehensive ASQ, as described previously [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF].

The study protocol was approved by Umeå University ethics committee and the study was conducted according to the declaration of Helsinki. Informed consent was obtained from all participants.

Assessments

Abdominal Symptom Questionnaire (ASQ) is a questionnaire assessing symptoms from the upper and lower part of the abdomen, and it has been found to be valid, reproducible and reliable [START_REF] Agréus | Reproducibility and validity of a postal questionnaire. The abdominal symptom study[END_REF]. All participants were asked if they had been troubled by abdominal pain or discomfort at any location or by any of the listed 33 other gastrointestinal symptoms [START_REF] Agréus | Reproducibility and validity of a postal questionnaire. The abdominal symptom study[END_REF]. The extended ASQ filled in at the EGD visit also included the grading of severity and the frequency of each symptom (daily, weekly or last 3 months). The participants´ medication use during the previous 3 months was recorded.

Demographic data and history

Demographic data were collected at the clinic visit (sex, age, length and weight, use of different tobacco products, use of alcohol and use of medication). The subjects' level of education (low education = elementary, comprehensive or secondary school, high education = upper secondary school or university) was asked at the clinic visit.

Definition of body mass index (BMI) BMI was calculated and categorized according to World Health Organization recommendations [START_REF]Obesity; preventing and managing the global epidemic[END_REF].

Definitions of symptom groups

Gastroesophageal reflux symptoms (GERS) were defined as the presence of any troublesome heartburn and/or acid regurgitation over the past three months [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF][START_REF] Ronkainen | High prevalence of gastroesophageal reflux symptoms and esophagitis with or without symptoms in the general adult Swedish population: A Kalixanda study report[END_REF].

Dyspepsia was defined as epigastric troublesome pain or discomfort, and/or nausea, early satiety or uncomfortable feeling of fullness after meal. This is consistent with the Rome II definition (except for upper abdominal bloating which was not asked about in the ASQ) [START_REF] Drossman | ROME II. The Functional Gastrointestinal Disorders[END_REF].

A simple definition of dyspepsia, labelled "epigastric pain or discomfort", based on the Rome I definition of dyspepsia, was also used [START_REF] Drossman | The Functional Gastrointestinal Disorders[END_REF].

Irritable bowel syndrome (IBS) was defined as troublesome abdominal pain or discomfort located at any site plus concomitant bowel habit disturbances (constipation, diarrhoea, or alternating constipation and diarrhoea). This definition has been used previously and shown to produce results reasonably concordant with the Rome criteria in Sweden [START_REF] Agréus | Identifying dyspepsia and irritable bowel syndrome: the value of pain or discomfort, and bowel habit descriptors[END_REF].

Abdominal pain was defined as troublesome pain or discomfort indicated anywhere in the abdomen [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF].

No or minor gastrointestinal symptoms were symptoms not fulfilling any of the above symptom classifications, or absence of symptoms in the ASQ.

Smoking cigarettes and snus use

A complete medical history was taken after the blinded upper endoscopy. The participants were asked about their present and past snus use and the current amounts/week and also about their smoking habits and the number of cigarettes per day in a standardized fashion.

Definitions of tobacco user categories

Current snus users were individuals using moist snuff or chewing tobacco (n=1), without any present or former use of smoked tobacco.

Current smokers were individuals smoking cigarettes without any present or former snus use.

Current users of both were individuals currently both smoking cigarettes and using snus Former smokers were former cigarette smokers without present or former snus use.

Former snus users were former snus users without present or former smoking cigarettes.

Former users of both were former cigarette smokers and snus users without present smoking or snus use.

Non-users were individuals who had never used tobacco products.

Esophagogastroduodenoscopy (EGD)

The upper endoscopies were provided by three experienced endoscopists in Kalix and Haparanda which gave sole medical cover to the area. Internal validity was assessed by means of consensus sessions [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF]. The endoscopists had been participating in regular quality assessment programs over several years. The endoscopists were unaware of the symptoms of the subjects before and during the endoscopy [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF].

Definition of gastric and duodenal ulcer

Peptic ulcer was defined as a mucosal break at least 3 millimetres in diameter in either the stomach or duodenum [START_REF] Aro | Peptic ulcer disease in a general adult population. The Kalixanda study: A random population-based study[END_REF].

Definition and classification of erosive esophagitis

The subjects with mucosal breaks in the esophagus were classified as having erosive esophagitis and graded according to the Los-Angeles classification [START_REF] Lundell | Endoscopic assessment of oesophagitis: clinical and functional correlates and further validation of the Los Angeles classification[END_REF].

Histology and Helicobacter pylori

Two experienced pathologists (M. V. and M. Stolte), who were unaware of the endoscopy findings, evaluated the biopsies and provided a common report. The biopsies were stained with haematoxylin and eosin. Helicobacter pylori was detected by Warthin-Starry silver staining [START_REF] Storskrubb | A negative Helicobacter pylori serology test is more reliable for exclusion of premalignant gastric conditions than a negative test for current Hp infection: A report on histology and Helicobacter pylori detection in the general adult population[END_REF].

Histological parameters of the gastric mucosa were assessed by using the updated Sydney System definitions [START_REF] Dixon | Classification and grading of gastritis. The updated Sydney System. International Workshop on the Histopathology of Gastritis, Houston[END_REF].

Chemical-reactive gastritis proposed to be caused by aspirin, NSAIDs, alcohol or bile reflux was defined according to the updated Sydney System definitions [START_REF] Dixon | Classification and grading of gastritis. The updated Sydney System. International Workshop on the Histopathology of Gastritis, Houston[END_REF][START_REF] Dixon | Bile reflux gastritis and intestinal metaplasia at the cardia[END_REF].

Samples from the antrum and corpus were cultured and analysed as described previously [START_REF] Storskrubb | A negative Helicobacter pylori serology test is more reliable for exclusion of premalignant gastric conditions than a negative test for current Hp infection: A report on histology and Helicobacter pylori detection in the general adult population[END_REF].

Current Helicobacter pylori infection was defined as a positive culture or histology. There was an overall agreement of 99.3 percent between the two methods [START_REF] Storskrubb | A negative Helicobacter pylori serology test is more reliable for exclusion of premalignant gastric conditions than a negative test for current Hp infection: A report on histology and Helicobacter pylori detection in the general adult population[END_REF].

Serology

Helicobacter pylori IgG antibodies were determined by EIA (Pyloriset EIA-G, Orion diagnostica, Espoo Finland) [START_REF] Lerang | Accuracy of seven different tests for the diagnosis of Helicobacter pylori infection and the impact of H2-receptor antagonists on test results[END_REF]. A positive test in the absence of Helicobacter pylori detection by culture or histology was considered indicative of a past infection.

Gastrin-17 (cut off ≥10 pmol/liter) and Pepsinogen-1 (cut off <25 μg/l for low and >100 μg/l for high levels) were analysed using specific EIA tests (Biohit Plc, Helsinki, Finland).

Statistical analysis

Pearson χ 2 test was used for testing comparisons in univariate analysis. The associations of tobacco user categories with GERS, dyspepsia, epigastric pain, abdominal pain, no or minor GI symptoms and IBS were analyzed applying logistic regression models including possible confounders; Helicobacter pylori infection, use of aspirin, use of non-steroidal antiinflammatory drugs, use of acid reducing drugs, high alcohol consumption (≥100 g/week), education level and categorized BMI and adjusting for age and sex and using non-users as the reference group (odds ratio (OR) = 1). The associations of tobacco user categories with esophagitis, gastric ulcer, duodenal ulcer, overall PUD, high Pepsinogen-1 level, high Gastrin-17 level and dichotomized histological variables from the esophagus, stomach and duodenum were analyzed applying multivariate logistic regression models including possible confounders; Helicobacter pylori infection, use of aspirin, use of non-steroidal antiinflammatory drugs, high alcohol consumption, education level, categorized BMI, use of acid reducing drugs and GERS and adjusting for age and sex and using non-users as the reference group (OR=1).

Associations with PUD were also analyzed using smokers as the reference group (OR=1). The results were controlled for interactions. Age and gender in all analyses and use of aspirin/NSAIDs, high alcohol consumptin, gastroesophageal reflux and Helicobacter pylori infection were the variables tested as possible effect modifiers. Stepwise model improvement was applied in all analyses to determine the most suitable multivariate logistic regression model and all analyses were adjusted at least for categorized (15 year bands) age and sex. The results from crude logistic regression models are also presented. The results are presented as odds ratios (OR) with 95% confidence interval (95% CI). The goodness of fit of the models was judged from the Pearson χ 2 test (acceptable model when p>0.05). A two sided P-value of <0.05 was regarded as statistically significant. Fisher's exact test was used in appropriate analyses. The STATA 8 program (Stata Corporation. College Station, TX, USA) was used for the analyses [START_REF]The Intercoold STATA 8 program[END_REF].

RESULTS

Of the 1,001 subjects endoscoped, 12 did not have data on the snus use or cigarette smoking, leaving 989 subjects for analysis. Of these, 96 (9.7%) were current snus users, 165 (16.7%) were current cigarette smokers, 22 (2.2%) were combined users, 209 (27.7%) were former smokers, 16 were former snus users and 49 former users of both. Overall 432 (43.7%) individuals had never smoked or used snus. The snus users consumed on average 3.2 cans/week (1 can=24-50 g), smokers consumed on average 11.5 cigarettes/day and combined snus users/smokers consumed 2.2 cans/week and 6.2 cigarettes/day. The sex distribution, age groups in 15 year bands, mean BMI, use of aspirin, alcohol consumption and education level in different user and non-user groups are shown in Table 1.

Use of proton pump inhibitors, histamine-2 receptor antagonists and antacids during the last week or during the last 3 months before the EGD was not significantly associated with smoking cigarettes or snus use.

Symptoms

Symptom prevalences in different tobacco user categories are shown in Table 2. Associations with GERS, IBS, dyspepsia, epigastric pain, overall abdominal pain and no or minor symptoms are shown in Table 3. No symptom groups were associated with snus use.

Endoscopy and histology

The prevalences of esophagitis, gastric ulcer, duodenal ulcer and overall PUD, split by tobacco use category, are presented in Table 4 and the associations of different tobacco user categories with esophagitis, gastric ulcer, duodenal ulcer and overall PUD are presented in Table 5.

Esophagus Snus users had a significantly higher prevalence of macroscopic esophagitis in univariate analyze compared with non-users (P=0.04, Table 4). However, snus was not associated with esophagitis in multivariate analyze adjusting for age and sex (Table 5).

Former snus use was associated with hyperplasia of the basal cell layer 2 cm above the esophago-gastric junction (crude logistic regression model, OR=4.43, 95% CI: 1.54, 12.74) and logistic regression model ajdusting for GERS, categorized age (15 year bands) and sex (OR=3.79, 95% CI: 1.28, 11.16). Also former cigarette smoking shows an association with hyperplasia of the basal cell layer in crude model (OR=1.50, 95% CI: 1.03, 2.17) and in logistic regression model ajdusting for GERS, Helicobacter pylori infection, categorized age and sex the result is nearly significant (OR=1.41, 95% CI: 0.97, 2.06). Male sex was also asociated with hyperplasia of basal cell layer at this location (OR=1.39, 95% CI: 1.02, 1.89) as was the oldest age group (≥ 65 years old individuals). Helicobacter pylori infection did not have any impact on histological changes 2 cm above the esophago-gastric junction.

Snus use was associated with hyperplasia of the basal cell layer (crude logistic regression model, OR=1.98, 95% CI: 1.19, 3.31 and logistic regression modell adjusting for GERS, Helicobacter pylori infection, categorized age and sex, OR=1.74, 95% CI: 1.02, 3.00) and with elongation of papillae (crude modell. OR=2.02, 95% CI: 1.23, 3.35 and logistic regression model adjusting for GERS, Helicobacter pylori infection, categorized age and sex, OR=1.79, 95% CI: 1.05-3.05) of the squamous epithelium at the esophago-gastric junction; both are histological markers of cell turnover due to chronic chemical irritation such as occurs in GERD. GERS was also a associated both with hyperplasia of basal cell layer and elongation of papillae at this location (OR=1.42, 95% CI: 1.07, 1.88 and OR=1.66, 95% CI: 1.26, 2.21 respectively). Helicobacter pylori infection was negatively associated with both these histological changes (OR=0.71, 95% CI: 0.53, 0.95 and OR=0.69, 95% CI: 0.51, 0.92). These results were not confouded by sex or age.

Stomach

Current

Helicobacter pylori and serology

Helicobacter pylori infection prevalence and seropositivity are presented in Table 6. There were no significant associations between current Helicobacter pylori infection or seropositivity and different tobacco product user groups. The proportion of cag-A positive Helicobacter pylori genotypes did not differ significantly between non-users and different tobacco product user groups.

Gastrin- In this study, 19% of men and 5% of women were current snus users, which are consistent with the Swedish average, of 21% of men and 4% of women. In addition the amounts consumed are also comparable to use in Sweden (3 cans/week) [START_REF] Bolinder | Cardiovascular Mortality and Risk Factors[END_REF]. The study population has been shown to be representative of the Swedish general population [START_REF] Aro | Valid symptom reporting at upper endoscopy in a random sample of the Swedish adult general population. The Kalixanda study[END_REF]. We believe that the results are likely to be generalizable to most Western populations including those were snus is used.

Smoking was a significant risk for PUD while snus users had less PUD than expected although the latter observation did not reach statistical significance. The reasons for this difference are uncertain. Snus contains high amounts of nitrate [START_REF] Hoffmann | Toxic and carcinogenic agents in dry and moist snuff[END_REF], which is associated with an increased nitrite formation in the oral cavity and further to formation of nitric oxide in the stomach [START_REF] Tannenbaum | The effect of nitrate intake on nitrite formation in human saliva[END_REF][START_REF] Lundberg | Intragastric nitric oxide production in humans: measurements in expelled air[END_REF][START_REF] Lundberg | Inorganic nitrate is a possible source for systemic generation of nitric oxide[END_REF]. In contrast, cigarette smoking seems to be related to reduced levels of nitrite in saliva [START_REF] Marteus | Nitric oxide formation in the oropharygeal tract: possible influence of cigarette smoking[END_REF]. Salivary nitrite has marked gastro-protective effects through nitric oxide formation [START_REF] Björne | Nitrite in saliva increases gastric mucosal blood flow and mucus thickness[END_REF]. These effects include elevated gastric mucosal blood flow and increased mucus thickness. Acidified nitrite has bactericidal effects [START_REF] Carlsson | In vitro evaluation of a new treatment for urinary tract infections caused by nitratereducing bacteria[END_REF], possibly including Helicobacter pylori. Snus did not impact on Helicobacter pylori status significantly in this population even though there was a non-significant trend towards less Helicobacter pylori infection along with rising age in snus users. We observed that both snus use and cigarette smoking caused significantly higher levels of Pepsinogen-1 without affecting Gastrin-17 level. Thus, the difference in PUD prevalences seems not to be due to the Gastrin-17-acid axis.

Intravenously infused nicotine has been shown to decrease pancreatic bicarbonate secretion in animals [START_REF] Konturek | Mechanisms of nicotine-induced inhibition of pancreatic secretion of bicarbonate in the dog[END_REF]. Similarly, reduced bicarbonate has been causally related to a higher risk of PUD in cigarette smokers [START_REF] Kikendall | Effect of cigarette smoking on gastrointestinal physiology and non-neoplastic digestive disease[END_REF]. There are no studies examining this effect in snus users, whose serum nicotine levels are similar to or higher than those of smokers. The role of swallowed alkaline tobacco-contaminated saliva against the development of PUD is unclear in snus users.

Snus use was associated with histological findings in the esophagus consistent with GERD. In a human study the frequency of transient lower esophageal sphincter relaxation was increased by the nitric oxide generating solution. The nitric oxide generating solution also increased esophageal acid exposure [START_REF] Manning | Nitrogenous chemicals generated from acidification of saliva influence transient lower oesophageal sphincter relaxations[END_REF]. Whether swallowed alkaline tobacco-contaminated saliva, comprising tobacco specific nitrosamine compounds [START_REF] Hoffmann | Toxic and carcinogenic agents in dry and moist snuff[END_REF], has any role in the development of esophagitis is unclear.

Juice from snus contains high amounts of nitrate which can be reduced to nitrite in the oral cavity [START_REF] Tannenbaum | The effect of nitrate intake on nitrite formation in human saliva[END_REF][START_REF] Lundberg | Intragastric nitric oxide production in humans: measurements in expelled air[END_REF][START_REF] Lundberg | Inorganic nitrate is a possible source for systemic generation of nitric oxide[END_REF]. When saliva, including dietary nitrate, converted to nitrite, meets acidic gastric juice, the nitrite is converted to nitrous acid, nitrosative species and nitric oxide [START_REF] Lundberg | Intragastric nitric oxide production in humans: measurements in expelled air[END_REF][START_REF] Lundberg | Inorganic nitrate is a possible source for systemic generation of nitric oxide[END_REF][START_REF] Suzuki | Nitrate and nitrosative chemistry within Barrett's oesophagus during acid reflux[END_REF].

In healthy volunteers this potentially mutagenic chemistry appears to be focused at the gastric cardia [START_REF] Suzuki | Nitrate and nitrosative chemistry within Barrett's oesophagus during acid reflux[END_REF]. A study from the UK showed that both acid and nitric oxide alone can induce double-strand DNA breaks in non-dysplastic Barrett's esophagus and thus may contribute to the genetic rearrangements in the progression from Barrett's esophagus to esophageal adenocarcinoma [START_REF] Clemons | Nitric oxide and acid induce doublestrand DNA breaks in Barrett's esophagus carcinogenesis via distinct mechanisms[END_REF].

A recent Swedish study could observe an increased risk for esophageal squamous cell cancer and a slightly elevated risk for non-cardiac stomach cancer among snus users who had never smoked [START_REF] Zendehdel | Risk of gastroesophageal cancer among smokers and users of Scandinavian moist snuff[END_REF]. We could however not verify any premalignant mucosal changes in the stomach. A retrospective cohort study showed that snus use was associated with increased risk of pancreatic cancer as was also cigarette smoking [START_REF] Luo | Oral use of Swedish moist snuff (snus) and risk for cancer of the mouth, lung, and pancreas in male construction workers: a retrospective cohort study[END_REF]. A Swedish review on the possible harmful effects of snus use found that the carcinogenic effect is probably due to the content of tobacco specific nitrosamines [START_REF] Cnattingius | Hälsorisker med svenskt snus (Health risks with the use of Swedish moist snuff)[END_REF].

The strength of our study is the population-based study design. The response rate to all parts of the study was high, suggesting that the results are likely to be reliable and representative.

The ASQ-questionnaire is valid, reliable and reproducible [START_REF] Agréus | Reproducibility and validity of a postal questionnaire. The abdominal symptom study[END_REF]. Each participant was specifically asked about use of tobacco products in a face to face interview, and therefore underreporting use is less likely. The weakness is that we cannot provide any physiological data, aside from Gastrin-17 and Pepsinogen-1 levels, and due to the cross-sectional study design it is not possible to draw definite conclusions about any causal connections between exposure and different gastrointestinal disorders. The small number of individuals in some sub-groups is a limitation. Some of the analyses attaining levels of statistical significance (P<0.05) could be chance given the number of tests.

The possibility of higher odds of histological changes, as shown by us, and the possible risk of cancer shown in earlier studies [START_REF] Zendehdel | Risk of gastroesophageal cancer among smokers and users of Scandinavian moist snuff[END_REF][START_REF] Luo | Oral use of Swedish moist snuff (snus) and risk for cancer of the mouth, lung, and pancreas in male construction workers: a retrospective cohort study[END_REF] must be taken in account when advocating for using snus in smoking quitting programs [41]. There is no reason to believe, with Sweden as a vivid example, that addictive snus on an open market would be used only by ex-smokers. It is also important to note that concomitant smoking cigarettes and snus use seems to be more harmful than snus use only [START_REF] Chao | Cigarette smoking, use of other tobacco products and stomach cancer mortality in US adults: The Cancer Prevention Study II[END_REF].

In conclusion the snus use was associated with histological markers of increased proliferation of the squamous epithelium consistent with GERD at the esophago-gastric junction but snus does not increase the risk for self-reported upper gastrointestinal symptom groups or risk for PUD.

  This is the first population-based, endoscopic study on the effects of snus use and smoking cigarettes in the upper gastrointestinal tract. The snus use was associated with histological

	markers of chronic chemical irritation alike in gastroesophageal reflux disease (GERD) at the
	esophago-gastric junction. Smoking cigarettes, but not use of snus, was associated with
	overall PUD.
	17 and Pepsinogen-1
	Snus use or smoking cigarettes were not associated with abnormal gastrin-17 level but both
	were associated with high Pepsinogen-1 level (crude logistic regression model for snus
	(OR=2.13, 95% CI: 1.35, 3.36 and logistic regression model adjusting for GERS, age and sex,
	OR=2.01, 95% CI: 1.23, 3.28 and crude model for smoking cigarettes, OR=2.60, 95% CI:
	1.79, 3.77 adjusted logistic regression model OR= 3.01, 95% CI: 2.04, 4.44, respectively)
	without changing the Pepsinogen-1/Pepsinogen-2 ratio significantly.
	When all Helicobacter pylori infected, all with histological mucosal atrophy in the stomach
	and all proton pump inhibitor users were excluded, both snus use and smoking cigarettes were
	associated with high Pepsinogen-1 (crude logistic regression model for snus OR=2.71, 95%
	CI: 1.47, 5.02 and logistic regression model adjusting for GERS, age and sex OR=2.47, 95%
	CI: 1.27, 4.79 and (crude logistic regression model for smoking cigarettes, OR=3.88, 95% CI:
	2.29, 6.56 and adjusted logistic regression model, OR= 5.03, 95% CI: 2.89, 8.80,
	respectively) but not with abnormal Gastrin-17 levels. Male sex was a confounder (OR=1.9,
	95% CI: 1.26, 2.96) as was age groups older than 34 years (35-49 years OR=2.25, 95% CI:
	1.03, 4.88, 50-64 years OR=2.90, 95% CI 1.35, 6.25 and ≥65 years OR=4.67, 95% CI 2.00,

10.90). The mean value of Pepsinogen-1 for snus users was 91.8 μg/l (SD 36.4) and for cigarette smokers 102.8 μg/l (SD 37.9). The difference is not significant.

DISCUSSION

Table 2 .

 2 Three months period symptom group prevalences split by tobacco user category. Randomised, population-based, endoscopic study, Kalix and Haparanda, Sweden (the Kalixanda study), December 1998-June 2001.

	Tables 1, 2, 3, 4, 5 and 6.
	Table1.	Demographic data of tobacco user/non-user groups. Randomised, population-based, endoscopic study, Kalix and
	Haparanda, Sweden (the Kalixanda study), December 1998-June 2001.
			Non-user	Current	Current	Using both	Former snus	Former	Former user of
	Demographic variable		snus user	smoker		user	smoker	both
			n=432	n=96	n=165	n=22	n=16	n=209	n=49
	Proportion of men	38.2
	95% CI b		33.6, 42,8

b

Table 3 .

 3 Tobacco use and association with gastrointestinal symptoms (OR=1 for non-users). Randomised, population-based, endoscopic study, Kalix and Haparanda, Sweden (the Kalixanda study), December 1998-June 2001.

		Current snus user	Current smoker	Using both	Former snus user	Former smoker	Former user of both
	Symptom
		OR a	95% CI b	OR a	95% CI b	OR a	95% CI b	OR a	95% CI b	OR a	95% CI b	OR a	95% CI b
	GERS c	1.22 0.72, 2.06	0.9	0.60, 1.39 2.40 0.89, 6.56 1.89	0.65, 5.51	1.12 0.77, 1.65 0.83	0.40, 1.74

Table 4 .

 4 Prevalences of gastrointestinal findings split by tobacco user category. Randomised, population-based, endoscopic study, Kalix and Haparanda, Sweden (the Kalixanda study), December 1998-June 2001.

			Non-user	Current snus user	Current smoker	Using both	Former snus user	Former smoker	Former user of both
	Endoscopic		n=432		n=96		n=165	n=22		n=16		n=209		n=49
	finding	% e	95% CI c	% e	95% CI c	% e 95% CI c % e 95% CI c	% e	95% CI c	% e	95% CI c	% e	95% CI c
	Esophagitis	13.7 10.5, 16.9 21.9 a 13.6, 30.2 12.7 7.6, 17.8 18.2 2.1, 34.3 25.0 3.8, 46.2 16.3 11.3, 21.3 18.4	7.6, 29.2
	Gastric ulcer	1.6	0.4, 2.8	1.0 ‡	0.0, 1.8	3.6	0.8, 6.4	4.6 0.0, 13.2 0.0	-	2.4	0.3, 4.5	0.0	-
	Duodenal ulcer 1.9	0.6, 3.2	0.0	-	4.2	1.1, 7.3	4.6 0.0, 13.2 0.0	-	1.4	0.0, 3.0	2.0	0.0, 5.9
	Overall PUD b	3.5	1.8, 5.2	1.0 d	0.0, 1.8	7.9 3.8, 12.0 9.1 0.0, 21.1 0.0	-	3.8	1.2, 6.4	2.0	0.0, 5.9
	a Significant difference P<0.05
	b Peptic ulcer disease
	c 95 percent confidence interval
	d A user of chewing tobacco and using only < 5g/week
	e Prevalence

Table 5 .

 5 Tobacco use and associations with gastrointestinal findings (OR # =1 for non-users, n=432). Randomised, population-based, endoscopic study, Kalix and Haparanda, Sweden (the Kalixanda study), December 1998-June 2001.

		Current snus user	Current smoker	Using both	Former smoker	Former snus user	Former user of both
	Endoscopic		n=96		n=165	n=22		n=209		n=16		n=49
	finding
		OR d	95% CI b OR d	95% CI b OR d	95% CI b OR d	95% CI b OR d	95% CI b OR d	95% CI b
	Esophagitis	1.13	0.62, 2.08 1.07	0.61, 1.88 1.08	0.33, 3.60 1.09	0.66, 1.78 1.33	0.40, 4.43 0.74	0.32, 1.69
	Gastric ulcer	0.93 0.11, 8.08 c 2.6	0.84, 8.08 2.88	0.32, 26.23 1.49	0.46, 4.87	-	-	-	-
	Duodenal ulcer	-	-	2.20	0.77, 6.30 2.12	0.23, 19.46 0.64	0.17, 2.51	-	-	0.93	0.11, 8.11
	Overall PUD a	0.34	0.04, 2.69 2.36	1.06, 5.26 2.57	0.49, 13.55 1.00	0.41, 2.44	-	-	0.64	0.08, 5.23
	a Peptic ulcer disease
	b 95 percent confidence interval
	c A user of chewing tobacco and using only < 5g/week
	d Odds ratio

Table 6 .

 6 Helicobacter pylori prevalences in tobacco user/non-user groups (culture/histology and serology). Randomised, population-based, endoscopic study, Kalix and Haparanda, Sweden (the Kalixanda study), December 1998-June 2001.

	Hp a infection and	Non-user	Current snus user	Current smoker	Using both	Former smoker	Former user of	Former user of
	serology in age						snus	both
	groups	n	n	n	n	n	n	n
		Prevalence (95%	Prevalence (95%	Prevalence (95%	Prevalence (95%	Prevalence (95%	Prevalence (95%	Prevalence (95%
		CI) b	CI)	CI)	CI)	CI)	CI)	CI)
	Age 20-49	n=148	n=45	n=75	n=10	n=57	n=8	n=17
	Current Hp	16.2 (10.3, 22.1)	17.8 (6.6, 29.0)	21.6 (12.3, 30.9)	10.0 (0.0, 28.6)	29.8 (17.9, 41.7)	25.0 (0.00, 55.0)	35.3 (12.6, 58.0)
	infection
	Positive Hp	21.6 (15.0, 28.2)	26.7 (13.8, 39.6)	25.3 (15.5, 35.1)	20.0 (0.0, 44.8)	36.8 (24.3, 49.3)	25.0 (0.00, 55.0)	35.3 (12.6, 58.0)
	serology
	Age 50 +	n=284	n=51	n=90	n=12	n=152	n=8	n=32
	Current Hp	44.0 (38.2, 49.8)	33.3 (20.4, 46.2)	47.8 (37.5, 58.19)	33.3 (6.6, 60.0)	41.5 (33.7, 49.3)	37.5 (4.0, 71.0)	21.9 (7.6, 36.2)
	infection
	Positive Hp	53.2 (47.4, 59.0)	47.1 (33.4, 60.8)	60.0 (49.9, 70.1)	41.7 (13.8, 69.6)	55.3 (47.4, 63.2)	37.5 (4.0, 71.0)	31.3 (15.2, 47.4)
	serology
	All ages	n=432	n=96	n=165	n=22	n=209	n=16	n=49
	Current Hp	34.5 (30.0, 39.0)	26.0 (17.2, 34.8)	36.0 (28.7, 43.3)	22.7 (5.2, 40.2)	38.3 (31.7, 44.9)	31.3 (8.6, 54.0)	32.7 (19.6, 45.8)
	infection
	Positive Hp	42.4 (37.7, 47.1)	37.5 (27.8, 47.2)	44.2 (36.6, 51.8)	31.8 (12.3, 51.3)	50.2 (43.4, 57.0)	31.3 (8.6, 54.0)	32.7 (19.6, 45.8)
	serology

a Helicobacter pylori b 95 percent confidence interval

ACKNOWLEDGEMENTS

This study was supported in part by the Swedish Research Council, the Swedish Society of Medicine, Mag-Tarm Sjukas Förbund, the Norrbotten County Council, Sweden, and AstraZeneca R&D, Mölndal, Sweden.

The authors thank Biohit Plc (Helsinki, Finland) for analyzing Gastrin-17 and Pepsinogen levels and Professor Pentti Sipponen for valuable help in evaluating these results and Professor Manfred Stolte for evaluating the biopsies.