A C G C Tjan-Heijnen

Voogd

Jetske Ruiterkamp
email: jetskeruiterkamp@hotmail.com

M F Ernst

L De Munck

M Van Der Heiden-Van Der Loo

E Bastiaannet

L V Van De Poll-Franse

K Bosscha

V C G Tjan-Heijnen

A C Voogd

Improved survival of patients with primary distant metastatic breast cancer in the period of 1995 -2008. A nationwide population-based study in the Netherlands

Keywords: Breast cancer, metastatic disease, prognosis, surgery, systemic treatment

Improved survival of patients with primary distant metastatic breast cancer in the period of 1995-2008. A nationwide population-based study in the Netherlands

Results

The median survival was 1.42 years for patients diagnosed in the period 1995-1999, 1.61 years in the period 2000-2004 and 1.95 years in the period [2005][2006][2007][2008]. The improvement of the median survival was most pronounced for patients younger than 50 years. Patients receiving systemic treatment, locoregional radiotherapy or breast surgery had a significantly lower risk of death compared to patients not receiving these treatments.

Conclusions An improvement of 6 months is observed in the median survival of patients with primary distant metastatic breast cancer between 1995 and 2008.

The increased efficacy of chemotherapy and the introduction of targeted treatments are the most likely explanations for this improvement, which was most marked for younger patients.

Introduction

Approximately 3-10% of all patients with breast cancer have distant metastases at initial presentation, and this proportion has decreased only slightly during the last three decades [1,[START_REF] Ries | SEER cancer statistics review[END_REF]. As in general metastatic breast cancer cannot be cured, patients receive palliative treatment. These include hormonal treatment, chemotherapy and targeted therapy. Local treatment of the primary tumor is usually not part of the standard therapy and is only recommended in case of symptomatic local disease.

During the last fifteen years, important changes have taken place concerning systemic treatment for patients with metastasized breast cancer, such as the introduction of taxanes in the late nineties and aromatase inhibitors and targeted therapy like trastuzumab in the beginning of the twenty-first century.

A systematic review of trials has demonstrated that increased efficacy of chemotherapy and targeted treatments have resulted in important improvements in the survival of patients with metastatic or recurrent disease [START_REF] Mauri | Multipletreatments meta-analysis of chemotherapy and targeted therapies in advanced breast cancer[END_REF]. It would be interesting to know whether these improvements have also taken place in the general population among the patients with primary distant metastatic breast cancer, treated in routine clinical practice outside clinical trials.

In a previous study we reported an increased survival in the Netherlands of patients with primary metastatic breast cancer. In this study, which was based on 1,089 patients diagnosed in South-East Netherlands in the period 1975-2002, the median survival remained unchanged between 1975 and 1984, but increased from 17 months for the patients diagnosed in the period 1985-1994 to 20.5 months for those diagnosed in the period 1995-2002 [START_REF] Ernst | Trends in the prognosis of patients with primary metastatic breast cancer diagnosed between 1975 and 2002[END_REF].

In the current study, we analyzed the changes in prognosis for more than 8,000 patients with primary distant metastatic breast cancer diagnosed between 1995 and 2008 and followed until 2010, using nation-wide data of the Netherlands Cancer Registry. As described above, surgery of the primary tumor is not standard treatment in these patients, though several retrospective studies have shown an improvement in overall survival in patients who have received breast surgery [START_REF] Khan | Does aggressive local therapy improve survival in metastatic breast cancer?[END_REF][START_REF] Babiera | Effect of primary tumor extirpation in breast cancer patients who present with stage IV disease and an intact primary tumor[END_REF][START_REF] Rapiti | Complete excision of primary breast tumor improves survival of patients with metastatic breast cancer at diagnosis[END_REF][START_REF] Fields | Surgical resection of the primary tumor is associated with increased long-term survival in patients with stage IV breast cancer after controlling for site of metastasis[END_REF][START_REF] Gnerlich | Surgical removal of the primary tumor increases overall survival in patients with metastatic breast cancer. Analysis of the 1988-2003 SEER data[END_REF][START_REF] Blanchard | Association of surgery with improved survival in stage IV breast cancer patients[END_REF][START_REF] Ruiterkamp | Surgical resection of the primary tumour is associated with improved survival in patients with distant metastatic breast cancer at diagnosis[END_REF]. Therefore, we also analyzed the impact of surgical resection of the primary breast tumor, besides the role of systemic treatment. To establish whether improvement of prognosis had taken place, patients were divided into three periods, based on the year of diagnosis of their disease; 1995-1999, 2000-2004 and 2005-2008. The follow-up of these patients was completed until January 1, 2010. Information about the age of the patients at time of diagnosis and tumor size of the primary tumor was recorded. Clinical tumor size was used for patients who did not undergo surgery. Also, information was collected about the type of treatment received by the patients, including systemic treatment, loco-regional radiotherapy and surgery of the primary tumor. No details on the extent and completeness of the surgical procedure were available.

Patients and methods

Patients

Only the first line of systemic therapy was documented by the Netherlands Cancer Registry and information on the type of systemic treatment was only available for the type of treatment (hormone treatment, chemotherapy, targeted treatment), but not for the exact drugs used. Use of targeted treatment has only been documented since 2005.

Statistical analyses

Survival time was defined as the period between the date of diagnosis and the date of death or January 2010 for the patients who were still alive. Overall survival rates were calculated using the Kaplan-Meier method. The log-rank test was performed to evaluate significant differences between survival curves in univariate analyses. Multivariable analyses were carried out using Cox proportional hazards regression models. The variables inserted into the model were period of diagnosis (2000-2004 and 2005-2008 versus 1995-1999), age at diagnosis (50-69 and 70+ versus <50 years), tumor size (T3-4 versus T1-2), surgery of the primary tumor (yes versus no), loco-regional radiotherapy of the primary tumor (yes versus no) and the use of systemic treatment (yes versus no).

Hazard ratios (HR) with 95% confidence intervals (CI) and P-values were estimated with respect to the reference category for each covariate. The SAS computer package (version 9.2) was used for all statistical analysis (SAS Institute Inc., Cary, NC, USA, 1999).

Results

Patient characteristics

The proportion of patients with primary metastatic breast cancer (stage IV disease) decreased from 5.3% (2,688/51,226) in the period 1995-1999, to 5.0%

(2,916/58,679) in the period 2000-2004 and to 4.8% (2,427/50,690) in the period 2005-2008 (P=.003). The proportion of patients with a breast tumor of five centimeter or smaller (T1 and T2 classification) increased from 47% in the period 1995-1999 to 55% in the period 2005-2008 (Table 1). More than 20% of all patients with stage IV breast cancer were younger than 50 years, 37% were between 50 and 70 years and 42% were 70 years or older (Table 1). The proportion of patients in the age group of 50-69 year was somewhat higher in the period 2005-2008.

The proportion of patients receiving first-line systemic therapy remained rather stable during the three periods (Table 1). Loco-regional radiotherapy as first-line treatment was administered to 14% of all patients in the period 1995-1999, to 15% in the period 2000-2004 and to 11% in the period 2005-2008 (Table 1). The proportion of patients who underwent a resection of the breast tumor (either ablation of the breast or lumpectomy, with or without axillary lymph node dissection) decreased from 31% in the period 1995-1999 to 23% in the last period (Table 1).

Older patients were less likely to receive chemotherapy and targeted treatment and more likely to receive hormonal treatment as first-line treatment (Table 2). In the period 2005-2008, 20% of the patients <50 years received a targeted treatment, compared to 11% of the patients of 50-69 years and 3% of those of 70 years or older (P<.0001). Older patients were also less likely to undergo surgery and to receive loco-regional radiotherapy (Table 2). In the

Median survival

The median survival was 1.42 years for patients diagnosed in the period 1995-1999, 1.61 years in the period 2000-2004 and 1.95 years in the period 2005-8 2008 (Table 3 and Figure 1). The difference between the periods 1995-1999 and 2000-2004 and between the periods 2000-2004 and 2005-2008 were both statistically significant (P=.012 and P<.0001, respectively). When analyzed according to age group, the improvement of the median survival was most pronounced for patients of 50 years or younger between the periods 2000-2004 and 2005-2008 (Figure 2a and Table 3), with an increase of 2.44 to 3.60 years (P<.0001) and for patients aged 50-69 years between the periods 1995-1999 and 2000-2004 (Figure 2b and Table 3), with an increase from 1.34 to 1.83 years (P=.009). The median survival in patients of 70 years and older did not differ significantly between the three periods (Figure 2c and Table 3). In the first period the median survival was 1.10 years, in the second 1.07 years and in the last period 1.25 years.

Multivariable analysis

In the multivariable analysis, taking into account the age of the patients, the size of the primary tumor and the use of systemic treatment, surgery and radiotherapy, the HR's for mortality in the second and third period as compared to the first period were 0.95 (P=.08) and 0.83 (P<.0001), respectively (Table 4).

Older age and larger primary tumor size were associated with a higher mortality risk. Patients receiving systemic treatment (HR 0.34, 95% CI 0.32-0.37), locoregional radiotherapy (HR 0.79, 95% CI 0.73-0.86) or breast surgery (HR 0.64, 95% CI 0.60-0.68) had a significantly lower risk of death compared to the patients not receiving these treatments. The median survival of the patients undergoing surgery was 2.56 years, compared to 1.33 years for the patients without surgical treatment of the primary tumor (Figure 3).

A multivariable analysis according to age group, confirmed the increased prognosis of the patients treated in the period 2005-2008 (Table 5). The HR's for the patients treated in this period, as compared to those treated in the period 1994-1999 were 0.66 (95% CI 0.55-0.79) for patients younger than 50 years, 0.81 (95% CI 0.72-0.91) for those of 50-69 years old and 0.85 (95% CI 0.77-0.95) for patient of 70 years or older. In all age groups, the patients receiving systemic treatment, loco-regional radiotherapy or breast surgery had a significantly lower risk of death compared to the patients not receiving these treatments.

Discussion

According to the data of the Netherlands Cancer Registry, the median survival of patients with primary distant metastatic breast cancer has improved with 6 Most studies on trends in prognosis of patients with primary metastatic breast cancer are hospital-based [START_REF] Andre | Breast cancer with synchronous metastases: trends in survival during a 14-year period[END_REF], or also included patients with secondary metastatic disease or patients participating in randomized clinical trials comparing different lines of chemotherapy [START_REF] Dafni | Fifteen-year trends in metastatic breast cancer survival in Greece[END_REF][START_REF] Chia | The impact of new chemotherapeutic and hormone agents on survival in a population-based cohort of women with metastatic breast cancer[END_REF][START_REF] Gennari | Survival of metastatic breast carcinoma patients over a 20-year period[END_REF][START_REF] Largillier | Prognostic factors in 1038 women with metastatic breast cancer[END_REF]. The interval between the primary tumor and the diagnosis of metastatic disease is an important prognostic factor. Therefore, including patients with secondary metastatic disease might introduce bias when differences in the metastasis-free interval exist between patients treated in different time-periods. Inclusion of patients treated in trials could also lead to biased results as they tend to have a better prognosis than patients receiving the same treatment outside trials, probably because of the strict in-and exclusion criteria applied to trial populations [START_REF] Bijker | Effects of patient selection on the applicability of results from a randomised clinical trial (EORTC 10853) investigating breast-conserving therapy for DCIS[END_REF][START_REF]Results of chemotherapy for unselected patients with acute myeloblastic leukaemia: effect of exclusions on interpretation of results. The Toronto Leukemia Study Group[END_REF]. Similar to our study, a hospital-based study by Andre et al., including 724 patients, also showed an improvement in the median survival of 6 months; being diagnosed between 1994 and 2000 was associated with a 37% lower risk of mortality in comparison to patients diagnosed between 1987 to 1993 [START_REF] Andre | Breast cancer with synchronous metastases: trends in survival during a 14-year period[END_REF]. None of the studies described above covered a patient group treated after 2003. Our study, which contains data of patients treated until 2009, is the first to evaluate the possible impact in daily practice of the treatments that have been introduced mainly since that time, such as trastuzumab.

Patients with primary metastatic disease are thought to have more aggressive disease than patients with metastases diagnosed during follow-up after treatment of primary breast cancer, and therefore their prognosis might be poorer. On the other hand, use of chemotherapy and endocrine treatment in the adjuvant setting may induce drug resistance and leave fewer options for optimal systemic treatment when metastases occur. A large population-based study from Canada by Chia et al. on 2,150 patients with metastatic breast cancer, of whom only 21% had primary metastatic disease, showed that the median survival improved from 1.2 years for patients diagnosed in the period 1991-1992 to 1.6 years for those diagnosed in the period 1999-2001 [START_REF] Chia | The impact of new chemotherapeutic and hormone agents on survival in a population-based cohort of women with metastatic breast cancer[END_REF]. These figures suggest that there is not a large difference in the survival between patients with primary and secondary metastatic breast cancer.

The proportion of patients with stage IV breast cancer receiving first-line systemic treatment did not change during the study period. Therefore, the introduction of more effective drugs is the most likely explanation for the better prognosis of patients treated after 1999. The fact that the benefit was larger for patients younger than 50 years is supported by the more frequent use of targeted treatment among this age group in the period of 2005-2008, when 20% received targeted therapy as first-line treatment, compared to 11% of the patients between 50 and 70 years old and only 3% of those older than 70 years.

Patients of 70 years and older had a poor prognosis, which improved only slightly during the study period. This may be explained by the fact that chemotherapy and targeted treatment were less frequently used in the elderly.

Elderly patients were also less likely to undergo surgery or receive loco-regional radiotherapy. Other studies, with respect to the prognosis of elderly patients, show a significantly higher mortality risk in older patients with metastatic disease [START_REF] Rapiti | Complete excision of primary breast tumor improves survival of patients with metastatic breast cancer at diagnosis[END_REF][START_REF] Gnerlich | Surgical removal of the primary tumor increases overall survival in patients with metastatic breast cancer. Analysis of the 1988-2003 SEER data[END_REF][START_REF] Ruiterkamp | Surgical resection of the primary tumour is associated with improved survival in patients with distant metastatic breast cancer at diagnosis[END_REF]. Comorbidity and frailty are more common among older patients and limit the therapeutic choices [START_REF] Louwman | Less extensive treatment and inferior prognosis for breast cancer patients with comorbidity: a population-based study[END_REF]. This may be an important explanation for the fact that the prognosis in elderly women with metastatic breast cancer has improved much less than in women younger than 70 years.

In our study, surgical treatment of the primary tumor was associated with lower mortality in all age groups. During the study period, the proportion of patients treated with surgery decreased. In a previously published review of the literature we found a pooled hazard ratio of 0.65 (95% CI, 0.59-0.72) in favor of surgical treatment of the breast tumor [START_REF] Ruiterkamp | Impact of breast surgery on survival in patients with distant metastases at initial presentation. A systematic review of the literature[END_REF], which is almost equal to the HR calculated in the current study. One of the explanations for the effect of surgery is that removing the tumor will lower the tumor load and reduce the amount of circulating tumor cells in the blood, which is known to be an independent predictor of overall survival in patients with metastatic breast cancer [START_REF] Cristofanilli | Circulating tumor cells, disease progression, and survival in metastatic breast cancer[END_REF].

Nevertheless, the observational nature of our study does not allow us to draw strong conclusions about the causality of the association between surgery and survival. Loco-regional radiotherapy also appeared to be associated with a significant improvement of the median survival. A similar association was found in a study by Le Scodan et al., in which radiotherapy was an independent prognostic factor in multivariate analysis, with a hazard ratio of 0.70 (95% CI, 0.58 to 0.85) [START_REF] Scodan | Breast cancer with synchronoius metastases: survival impact of exclusive localregional radiotherapy[END_REF].

Our population-based study is based on information from more than 8,000 patients with primary distant metastatic breast cancer, gathered by the Netherlands Cancer Registry and including virtually all patients with stage IV breast cancer in the Netherlands. Information of patients diagnosed until 2009 was available, with follow-up until 2010, which allowed us to provide up-to-date results. Unfortunately, only first-line treatment was recorded and no data were available on the specific drugs used. This is clearly a limitation of a retrospective analysis based on cancer registry data. This may also explain why the sum of first-line hormonal therapy and chemotherapy is larger than 100%, that is, for some patients more than one treatment modality may have been recorded, perhaps in those who had an early switch because of non-responsiveness to the first initiated treatment. Obviously, also other biases may have occurred, for instance by patient selection for specific therapies like radiotherapy or surgery.

Twelve percent of the patients in our study did not receive systemic treatment. Some underreporting cannot be ruled out. However, in two other studies on prognosis of primary metastatic breast cancer by Blanchard et al. and Kahn et al. similar percentages, of 8% and 22% respectively, were reported [START_REF] Khan | Does aggressive local therapy improve survival in metastatic breast cancer?[END_REF][START_REF] Blanchard | Association of surgery with improved survival in stage IV breast cancer patients[END_REF]. Apparently, a substantial part of these patients present with very advanced, rapidly progressive disease for which systemic treatment is no viable option anymore.

Information on the use of targeted treatment was only available since 2005, as was also the case for the site of distant metastatic involvement. However, it is not very likely that these sites and the number of metastatic sites have changed much during the three time periods. Our study is covering a relatively short period, which makes it less likely that changes in radiologic facilities (except perhaps for the introduction of positron emission tomography) have had a large impact on the detection of metastatic disease. Moreover, the percentage of patients with metastatic disease has remained rather stable during the different time periods, also indicating that screening methods and indications for peri-operative screening for patients without clinical signs of metastases have not changed between 1995 and 2008. An increase in the amount of patients participating in the breast cancer screening program may have caused the increase in the proportion of patients with T1 and T2 tumors. However, in the multivariable analysis adjustments have been made for this shift in tumor size.

In conclusion, an overall improvement of 6 months is observed between breast cancer, resulting in a median survival of almost 2 years for the patients treated in the last period. This improvement was most pronounced in patients younger than 50 years. The increased efficacy of chemotherapy and the introduction of targeted treatments are the most likely explanation. Surgical removal of the primary breast tumor and loco-regional radiotherapy do also seem to have a positive impact on survival, but to be able to rule out selection bias, it would require a randomized study to quantify the added value of loco-regional treatment and tumor control to systemic therapy in the management of patients with stage IV breast cancer.

  Patients were selected from the population based Netherlands Cancer Registry. PALGA, the nationwide Dutch network and registry of histo-and cytopathology, regularly submits reports of all diagnosed malignancies to the regional cancer registries. The national hospital discharge databank, which receives discharge diagnoses of admitted patients from all Dutch hospitals, completes case ascertainment. Following this notification, trained registry personnel from the Netherlands Cancer Registry collect data on patient and tumor characteristics, diagnosis, staging and treatment. Coding of the items is based on the registration and coding manual of the Dutch Association of Comprehensive Cancer Centers. According to the database the Netherlands Cancer Registry, 160,595 new patients were diagnosed with invasive breast cancer in the period 1995-2008. Of these patients, 8,031 (5.0%) had distant metastases at diagnosis (stage IV disease).

  period 2005-2008, 38% of the patients <50 years underwent surgery, compared to 24% of the patients of 50-69 years and 15% of those of 70 years or older (P<.0001).

  months in the period 1995-2008, now reaching almost 2 years. The improvement was most pronounced in the period 2000-2004 for patients aged 50-69 years and in the period 2005-2008 for the patients younger than 50 years. These improvements were also confirmed by the results of the multivariable analysis, adjusting for potential confounders. Our nationwide study is one of the few large population-based studies on trends in prognosis of patients with primary metastatic breast cancer. Two other population-based studies analyzed data from the Surveillance, Epidemiology, and End Results (SEER) program [12,9]. The study by Dawood et al., involving 15,438 patients, showed an improvement of the median survival of 4 months between 1988 and 2003 [12]. In both studies, the increased prognosis of patients treated more recently was confirmed in a multivariable analysis. In a populationbased study by Rapiti et al., based on 300 patients diagnosed between 1977 and 1996 and documented by the Geneva Cancer Registry, an improvement of the breast cancer-specific survival was demonstrated in the unadjusted but not in the adjusted multivariable analysis [7]. In a previous population-based study, involving 1,089 patients treated in the southern part of the Netherlands, we observed an improvement of the median survival of 2.5 months for the patients treated in the period 1995-2002 as compared to those treated in the period 1975-1984 [4].

Table 1 :

 1 Characteristics of patients with primary metastatic breast cancer, according to period of diagnosis (N=8031)

	Characteristic			Period of diagnosis
		1995-1999	2000-2004	2005-2008
		(N=2688)	(N=2916)	(N=2427)
		N	(%)	N	(%)	N	(%)	P
	Age at diagnosis (year)							.003
	<50	543	(20)	642	(22)	519	(21)
	50-69	961	(36)	1065	(37)	965	(40)
	70+	1182	(44)	1209	(41)	943	(39)
	Tumor size							<.0001
	T1-2	1098	(47)	1275	(50)	1198	(55)
	T3-4	1233	(53)	1286	(50)	992	(45)
	Missing	357		299		237
	Surgery							<.0001
	Yes	831	(31)	810	(28)	563	(23)
	No	1857	(69)	2106	(72)	1864	(77)
	Radiotherapy							.002
	Yes	367	(14)	428	(15)	278	(11)
	No	2321	(86)	2488	(85)	2149	(89)
	Systemic treatment							.001
	Yes	2404	(89)	2514	(86)	2142	(88)
	No	284	(11)	402	(14)	285	(12)

Table 1 :

 1 Characteristics of patients with primary metastatic breast cancer, according to period of diagnosis (N=8031). (Continued)

	Characteristic			Period of diagnosis
		1995-1999	2000-2004	2005-2008
		(N=2688)	(N=2916)	(N=2427)
		N	(%)	N	(%)	N	(%)	P
	Chemotherapy							.001
	Yes	883	(33)	1086	(37)	906	(37)
	No	1805	(67)	1830	(63)	1527	(63)
	Hormonal treatment							.001
	Yes	1763	(66)	1781	(61)	1571	(65)
	No	925	(34)	1135	(39)	856	(35)
	Targeted treatment	Not available	Not available			Not
								applicable
	Yes					245	(10)
	No					2182	(90)

Table 3 :

 3 Median survival (yrs) and 95% confidence intervals of patients with primary metastatic breast cancer, according to age group and period of diagnosis

			Period of diagnosis
	Age group	1995-1999	2000-2004	2005-2008	P
	<50 yrs	2.29 (2.09-2.74)	2.44 (2.12-2.78)	3.60 (2.88-4.14)	<.0001
	50-69 yrs	1.34 (1.20-1.51)	1.83 (1.64-2.03)	2.07 (1.90-2.40)	<.0001
	70+ yrs	1.10 (0.92-1.25)	1.07 (0.92-1.18)	1.25 (1.08-1.38)	.200
	All patients	1.42 (1.33-1.53)	1.61 (1.51-1.70)	1.95 (1.80-2.08)	<.0001

Table 4 :

 4 Multivariable analysis for time until death for patients with primary metastatic breast cancer (N=7073)*

	Characteristic	HR**	(95% CI)	P
	Period of diagnosis
	1995-1999	1 (Ref)
	2000-2003	0.95	(0.89-1.01)	.081
	2004-2007	0.83	(0.77-0.89)	<.0001
	Age at diagnosis (years)
	<50	1 (Ref)
	50-69	1.33	(1.24-1.44)	<.0001
	70+	1.59	(1.48-1.71)	<.0001
	Tumor size
	T1-2	1 (Ref)
	T3-4	1.14	(1.08-1.20)	<.0001
	Surgery
	No	1 (Ref)
	Yes	0.64	(0.60-0.68)	<.0001
	Systemic treatment
	No	1 (Ref)
	Yes	0.34	(0.32-0.37)	<.0001
	Radiotherapy
	No	1 (Ref)
	Yes	0.79	(0.73-0.86)	<.0001

* 958 patients were not included in the multivariable because of missing information on tumor size ** HR = Hazard Ratio

Conflict of interest

The authors indicated no potential conflicts of interest.


M J Aarts

MSc A C Voogd

PhD L E M Duijm

PhD J W W Coebergh

PhD W J Louwman

Socioeconomic inequalities in attending the mass

Keywords: breast cancer, mass screening, socioeconomic factors, participation, stage at diagnosis, survival

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

Introduction

Breast cancer screening programs aim to reduce breast cancer mortality rates through early cancer detection. To optimize the effectiveness of the current screening programs it is especially important to reach women at high risk of advanced stage disease at diagnosis and concomitant lower survival rates.

In many countries, the proportion of women having a screening mammogram has been highest among those with high socioeconomic status (SES), independent of the presence of organized breast screening programs [START_REF] Kim | Socioeconomic disparities in breast cancer screening among US women: trends from 2000 to 2005[END_REF][START_REF] Moser | Inequalities in reported use of breast and cervical screening in Great Britain: analysis of cross sectional survey data[END_REF][START_REF] Peek | Disparities in screening mammography. Current status, interventions and implications[END_REF][START_REF] Zackrisson | Social predictors of non-attendance in an urban mammographic screening programme: a multilevel analysis[END_REF]. For example, between 2000 and 2005, in the U.S. 65% of women aged 40 years or older with a low income had a screening mammogram within the previous two years compared to 83% of women with a high income [START_REF] Kim | Socioeconomic disparities in breast cancer screening among US women: trends from 2000 to 2005[END_REF].

Patients with low SES have a more advanced stage distribution than those with high SES [START_REF] Dalton | The relation between socioeconomic and demographic factors and tumour stage in women diagnosed with breast cancer in Denmark, 1983-1999[END_REF][START_REF] Macleod | Socio-economic deprivation and stage of disease at presentation in women with breast cancer[END_REF][START_REF] Schrijvers | Deprivation, stage at diagnosis and cancer survival[END_REF],

which may be due to their lower screening attendance. Furthermore, breast cancer survival rates are highest among patients with high SES [START_REF] Schrijvers | Socioeconomic variation in cancer survival in the southeastern Netherlands, 1980-1989[END_REF][START_REF] Dalton | Influence of socioeconomic factors on survival after breast cancer--a nationwide cohort study of women diagnosed with breast cancer in Denmark 1983-1999[END_REF][START_REF] Louwman | Impact of a programme of mass mammography screening for breast cancer on socio-economic variation in survival: a population-based study[END_REF][START_REF] Gentil-Brevet | The influence of socioeconomic and surveillance characteristics on breast cancer survival: a French population-based study[END_REF]. Conflicting reports exist as to whether socioeconomic differences in breast cancer survival are due to socioeconomic differences in stage distribution [START_REF] Bastiaannet | Socioeconomic differences in survival among breast cancer patients in the Netherlands not explained by tumor size[END_REF][START_REF] Kaffashian | Socioeconomic effects on breast cancer survival: proportion attributable to stage and morphology[END_REF][START_REF] Carnon | Relation between socioeconomic deprivation and pathological prognostic factors in women with breast cancer[END_REF].

The presence of concomitant diseases may also partly explain a SES gradient in breast cancer survival [START_REF] Louwman | A 50% higher prevalence of life-shortening chronic conditions among cancer patients with low socioeconomic status[END_REF]. Socioeconomic inequalities in adherence to mammography screening have been found in several countries [START_REF] Kim | Socioeconomic disparities in breast cancer screening among US women: trends from 2000 to 2005[END_REF][START_REF] Moser | Inequalities in reported use of breast and cervical screening in Great Britain: analysis of cross sectional survey data[END_REF][START_REF] Peek | Disparities in screening mammography. Current status, interventions and implications[END_REF][START_REF] Zackrisson | Social predictors of non-attendance in an urban mammographic screening programme: a multilevel analysis[END_REF]. For the Netherlands, a country with equal access to screening and care for all women, these data are lacking. We hypothesized that Dutch women with low SES also show lower screening attendance rates, more advanced stage breast cancers and worse survival. Therefore, we conducted a regional study on SES and screening attendance and we explored the consequences of socioeconomic differences in attendance rate for the stage distribution at diagnosis and survival.

Materials and Methods

The population-based screening program for breast cancer in southern Netherlands (Bevolkings Onderzoek Borstkanker Zuid, BoBZ) was started in 1991 and fully implemented in 1996. The program initially offered biennial screening mammography to women aged 50-69 years; in 1998 the upper age limit was extended to 75. The attendance rate was more than 84% [16]. The BoBZ database was used to select all women invited for screening from 1998 to 2005. These women received an invitation letter 4/20 23-1-2011 approximately 2 weeks before the screening. Reminder letters with a new appointment were sent to women who did not appear.

The Eindhoven Cancer Registry (ECR) records data on all patients newly diagnosed with cancer in the southern part of the Netherlands, an area with currently 2.4 million inhabitants (about 15% of the Dutch population) and only non-university hospitals. Trained registry personnel actively collects data on diagnosis, staging (Tumor-Node-Metastasis [START_REF] Sobin | UICC International Union against Cancer. TNM Classification of malignant tumours[END_REF]), treatment and comorbidity (slightly adapted from Charlson [START_REF] Charlson | A new method of classifying prognostic comorbidity in longitudinal studies: development and validation[END_REF]) from the medical records after notification by pathologists and medical registration offices.

Previous admissions, letters from and to general practitioners and other specialists, medical history and preoperative screening were used as sources. Pathological and clinical TNM were combined into one variable, primarily referring to the pathological stage unless missing.

The regions of the BoBZ and ECR cover an area of approximately 2.2 million inhabitants. Linkage of the databases of BoBZ and the ECR enabled us to compare stage at diagnosis of patients who attended with those who did not attend screening in the two years preceding diagnosis. Only invasive breast cancers and ductal carcinoma in situ (DCIS) were included. Screen-detected breast cancers were defined as registry-ascertained cancers if breast cancer had been diagnosed within 1 year following positive screening mammography (i.e., a woman had been referred for evaluation of a screening abnormality). Interval cancers were registry-ascertained cancers if 1) breast cancer had been diagnosed within 24 months following a negative screen (i.e., a woman had not been referred after screening mammography); or 2) breast cancer had been diagnosed 12-24 months after a positive screen. Patients with breast cancer diagnosed more than 2 years after screening mammography were considered to have not attended the screening program.

Statistics Netherlands developed an indicator of SES, using individual fiscal data based on the economic value of the home and household income. This SES indicator is provided at an aggregated level for each postal code (covering an average of 17 households). SES was categorized as low (deciles 1-3), medium (deciles 4-7), or high (deciles 8-10). A separate class was used for postal codes in areas comprising a long-term care providing institution (such as a nursing home) [START_REF] Van Duin | Sociaal-economische status indicator op postcodeniveau[END_REF].

Statistics

Statistical analyses were performed using SAS version 9.1 (SAS Institute Inc., Cary, NC, USA). All tests were two-sided and considered significant if p≤0.05. The distribution of sociodemographic and 5/20 23-1-2011 clinical characteristics were studied across the SES strata. Significance was tested with non-parametric tests (continuous variables) and χ 2 -tests (categorical variables). Attendance rates according to SES were computed according to year of invitation and age category. Stage comparisons were based on invasive and non-invasive tumors. Survival analyses were based on invasive cancers only. Survival time was defined as the time from diagnosis to death or January 1 st , 2009 for the patients who were still alive.

Survival analyses were stratified into 1) screen-detected cancers, 2) interval cancers 3) patients who did not attend the screening program. Univariate SES differences in survival were evaluated with the log rank test. The crude survival was calculated with the life test method and the independent prognostic effect of SES was estimated using Cox regression analyses. The hazard rates for death were adjusted for age (51≤60 versus ≤50, 61≤70, 71≤75 or ≥76). Subsequently we added the mediators stage (stages I versus II, III, IV or unknown) and therapy (surgery+radiotherapy versus surgery+radiotherapy+systemic therapy, surgery alone, surgery+systemic therapy or systemic therapy alone/other therapy/unknown), and the confounder comorbidity (no versus yes or unknown), and the combination of these to investigate whether the effect of SES on prognosis could be explained by differences in stage, treatment or comorbidity. Hazard ratios (HR) with 95% confidence intervals were reported. The relative contributions of comorbidity, treatment or stage were calculated with the formula: (((HR model adjusted for age) -(HR model adjusted for age +comorbidity or stage or treatment))/(HR model adjusted for age -1))*100.

Results

Attendance rates

From 1998 to 2005, the BoBZ sent 1,112,263 invitations for breast examination to women living in the area covered by the ECR. Those with unknown SES [START_REF] Gentil-Brevet | The influence of socioeconomic and surveillance characteristics on breast cancer survival: a French population-based study[END_REF]166) and those living at a postal code that includes an institution, such as nursing homes or rehabilitation centers, [START_REF] Visser | Results of breast cancer screening in first generation migrants in Northwest Netherlands[END_REF]145) were excluded, leaving data of 1,067,952 invitations to be analyzed (Figure 1, Table 1).

Attendance rates showed a positive correlation with increasing SES and were respectively 79%, 85% and 87% for women with low, intermediate or high SES (p<0.001). Among screening attendees, the first screening mammography was made for 12%, 14% and 15% of low, intermediate and high SES.

During the study period, attendance increased slightly from 77%, 84% and 86% to 80%, 87% and 88% for low, intermediate and high SES (Figure 2). The socioeconomic inequalities in screening attendance 6/20 23-1-2011 was significant in all years and in all age categories (p<0.001). Among non-attendees, women with high SES more often informed the screening organization about their refusal (54%) than women with low SES (38%). The most common reason for not attending the screening was "having a self-reported medical condition related to the breast."

After adjustment for age and year of invitation, an odds ratio (OR) for attending breast screening of 1.75 (95% confidence interval: 1.7-1.8) was found if comparing women with high SES to women with low SES, whereas women with intermediate SES had an OR of 1.54 (95% CI: 1.5-1.6, Table 1). The odds of attending the screening increased from the age of 50 until 70 and with each year of invitation.

Stage at diagnosis

From 1998 to 2006 6,086 women eligible for screening were diagnosed with invasive breast cancer or DCIS in the overlapping regions of the BoBZ and IKZ. After exclusion of patients with noncarcinoma (N=22: 3 benign neoplasms NOS; 1 leiomyosarcoma NOS; 2 carcinosarcomas NOS; 2 malignant myoepitheliomas; 12 phyllodes tumours; 2 hemangiosarcomas), data on 6,064 patients could be analyzed (Figure 1). Among patients with screen-detected cancer, those with high SES had slightly more in situ tumors and less stage 1 tumors (17% versus 12% in situ and 56% versus 52% stage 1, p<0.01, Figure 3). For patients with interval cancer, stage 4 disease was significantly less common in the high SES group compared to the low SES group (2% versus 8%, p<0.05). Within the SES groups of both screen-detected and interval cancers, no differences were observed in stage distribution between tumors detected by the initial screening mammogram versus those detected by subsequent mammograms (data not shown).

Among non-attendees, stage 4 cancers were found in respectively 10% and 5% of women with low SES or high SES (p<0.01). No significant differences in stage distribution were found for low versus intermediate and intermediate versus high SES in non-attenders.

In low stages of disease treatment differences were present. In stage 1, high SES patients more often received radiotherapy in addition to surgery for screen-detected cancers, and less often received surgery alone or the combination of surgery, radiotherapy and systemic therapy for interval cancer. In stage 2, surgery plus radiotherapy was less common in high SES patients with interval, while high SES patients who did not attend the screening program more often received surgery alone.

7/20

23-1-2011 Survival Complete follow up had been obtained of all but 18 (0.3%) patients with invasive cancer. Crude five-year survival was 89% among screening attendees (N=4,098), more specifically 83% in interval cancers (N=852), 91% in screen-detected cancers (N=3,246), and 77% among non-attendees (N=1,233, log-rank test p<0.001). A socioeconomic gradient in survival was observed, with worst survival for women with low SES and best survival for women with high SES (Figure 4). Patients with low SES and screen-detected cancer had worse survival (89%) compared to patients with intermediate SES (91%, log rank-test p<0.01) and high SES (91%, p<0.01). Patients with low SES and interval cancer had a worse survival (81%) compared to those with high SES (89%, p<0.01), and those with intermediate SES and interval cancer had worse survival rates than those with high SES as well (81%, p=0.02). Within the groups of screen-detected and interval cancer, no significant differences were observed for survival of initial versus subsequent screening rounds, although survival rates were generally slightly higher for cancers detected at subsequent screening mammography (data not shown). Patients with low SES and who had not attended screening showed significantly worse survival compared to women with intermediate SES (crude 5-year survival 74 versus 77%, log rank test: p<0.01) and high SES (81%, p<0.001).

The socioeconomic inequalities in survival remained after age adjustment, with a hazard ratio (HR) of 1.4 (1.1-1.9) for low SES if compared to high SES in non-attendees, and 1.3 (1.0-1.7) and 1.7

(1.1-2.6) for screen-detected cancers and interval cancers (Table 2). As comorbidity was inversely associated with SES (46%, 39% and 32% in low, intermediate and high SES), we additionally adjusted for comorbidity in the age-adjusted model. Socioeconomic inequalities in breast cancer survival seemed to be related to socioeconomic inequalities in presence of comorbidities in screen-detected cancers (23%), but had less impact in interval cancers or in non-attenders. In these latter two groups, survival disparities seemed to be largely related to stage, which explained respectively 35% and 48% of the survival disparities, while treatment had a minor role (16% and 16%, respectively).

Discussion

The current study shows that women with high SES show higher attendance rates for breast cancer screening in the south of the Netherlands. Socioeconomic inequalities persist resulting in significantly worse stage and lower survival for women with low SES. Compared to other European countries, Dutch screening attendance rates are rather high: 84% compared to 65% in Sweden (1990Sweden ( -2003, clinical trial) , clinical trial) [START_REF] Zackrisson | Non-attendance in breast cancer screening is associated with unfavourable socio-economic circumstances and advanced carcinoma[END_REF], 73% in England (3-year screening, 2007-2008) [START_REF]The Health and Social Care Information Centre: Breast screening programme[END_REF] and 63% (1999)(2000)(2001) in Copenhagen [START_REF] Vejborg | Early outcome of mammography screening in Copenhagen 1991-99[END_REF]. Comparable attendance rates were reported in another Danish region (around 84% from 1991-2001 [START_REF] Von Euler-Chelpin | Women's patterns of participation in mammography screening in Denmark[END_REF]) and in a Spanish screening program (82%, 1995-1998) [START_REF] Bare | Factors related to non -participation in a population-based breast cancer screening programme[END_REF]. The socioeconomic inequalities in attendance rates in this study (OR 1.75 for high compared to low SES) are somewhat smaller than the results presented by others, although the magnitude seems to depend on the SES indicator used [START_REF] Moser | Inequalities in reported use of breast and cervical screening in Great Britain: analysis of cross sectional survey data[END_REF][START_REF] Zackrisson | Non-attendance in breast cancer screening is associated with unfavourable socio-economic circumstances and advanced carcinoma[END_REF][START_REF] Duport | Do socio-demographic factors influence mammography use of French women? Analysis of a French cross-sectional survey[END_REF]. Studies on the association with education however have given mixed results, with some showing higher educational levels had a tendency toward lower non-attendance rates [START_REF] Moser | Inequalities in reported use of breast and cervical screening in Great Britain: analysis of cross sectional survey data[END_REF][START_REF] Duport | Do socio-demographic factors influence mammography use of French women? Analysis of a French cross-sectional survey[END_REF] and one study shown higher [START_REF] Zackrisson | Non-attendance in breast cancer screening is associated with unfavourable socio-economic circumstances and advanced carcinoma[END_REF] non-attendance rates. A U-shaped association has also been reported [START_REF] Von Euler-Chelpin | Does educational level determine screening participation?[END_REF].

In contrast to many European countries, breast cancer screening in the U.S. is done opportunistically. This may contribute to the larger socioeconomic inequalities in attendance rates in the U.S., where around 60% of women with low and 75-80% with high income (or education) (self)reported to have had a mammogram or clinical breast examination in the past 2 years [START_REF] Kim | Socioeconomic disparities in breast cancer screening among US women: trends from 2000 to 2005[END_REF][START_REF] Peek | Disparities in screening mammography. Current status, interventions and implications[END_REF][START_REF]American Cancer Society: Cancer Prevention & Early Detection Facts & Figures[END_REF][START_REF] Coughlin | Breast cancer screening practices among women in the United States, 2000[END_REF]. In line with the trend we observed, U.S. participation rates increased over time from 77% (1988-1990) to even 92% (1998)(1999)(2000) in the health-aware nurses in the Nurses Health Study [START_REF] Cook | Mammographic Screening and Risk Factors for Breast Cancer[END_REF].

Not attending screening may be related to inadequate knowledge of cancer, attitudes, health consciousness, cultural differences, language problems and illiteracy [START_REF] Peek | Disparities in screening mammography. Current status, interventions and implications[END_REF][START_REF] Lale | Factors associated with non-participation of Turkish women to cervical cancer screening in the Netherlands[END_REF]. These are all more often seen in people with low SES [START_REF] Stein | Prevalence and sociodemographic correlates of beliefs regarding cancer risks[END_REF][START_REF] Wardle | Socioeconomic differences in attitudes and beliefs about healthy lifestyles[END_REF] and could thus have contributed to the socioeconomic gradient in attendance rate. In the Netherlands, immigrants were found to have lower attendance rates [START_REF] Visser | Results of breast cancer screening in first generation migrants in Northwest Netherlands[END_REF], which might be attributed to a lack of proficiency of the Dutch language [START_REF] Lale | Factors associated with non-participation of Turkish women to cervical cancer screening in the Netherlands[END_REF]. Nowadays, the Dutch screening organization has invitations and accompanying information leaflets in the Dutch, English, Turkish and Arabic language. Presence of financial and health system barriers also have been suggested as reasons for not attending the screening [START_REF] Peek | Disparities in screening mammography. Current status, interventions and implications[END_REF]. However, the Dutch government offers mammographies free of charge, thus this is unlikely to play a role in the Netherlands. Because non-attendees are not inclined to seek mammography elsewhere [START_REF] Jensen | Do nonattenders in mammography screening programmes seek mammography elsewhere?[END_REF], it is very important to reach all women for screening.

In previous studies having a low SES has also been associated with more advanced stage at diagnosis [START_REF] Dalton | The relation between socioeconomic and demographic factors and tumour stage in women diagnosed with breast cancer in Denmark, 1983-1999[END_REF][START_REF] Macleod | Socio-economic deprivation and stage of disease at presentation in women with breast cancer[END_REF][START_REF] Schrijvers | Deprivation, stage at diagnosis and cancer survival[END_REF][START_REF] Gentil-Brevet | The influence of socioeconomic and surveillance characteristics on breast cancer survival: a French population-based study[END_REF][START_REF] Adams | Are there socioeconomic gradients in stage and grade of breast cancer at diagnosis? Cross sectional analysis of UK cancer registry data[END_REF] but to our knowledge this has not been studied in association with attendance to screening. It is likely that at least part of this association can be attributed to socioeconomic inequalities in attendance rates of screening programs. For example, 36-47% of the breast tumors in Switzerland is 9/20 23-1-2011 stage 2 or higher in regions with screening programs, compared to 50-64% in regions without a screening program [START_REF] Bulliard | Effectiveness of organised versus opportunistic mammography screening[END_REF]. Studies from Italy and Sweden found comparable results [START_REF] Zackrisson | Non-attendance in breast cancer screening is associated with unfavourable socio-economic circumstances and advanced carcinoma[END_REF][START_REF] Cortesi | Prognosis of screendetected breast cancers: results of a population based study[END_REF]. Not surprisingly, patients who attended screening had a more favorable stage distribution than those who did not attend, and patients with high SES had less advanced tumors than low SES. Remarkable socioeconomic stage differences were observed in screen-detected cancer, suggesting other tumor biology [START_REF] Taylor | Social deprivation and breast cancer[END_REF]. In screen-detected cancers, we observed small differences in morphology (65% had infiltrating duct carcinoma versus 71% in low SES), estrogen receptor status (88% ER+ versus 85%) and progesterone receptor status (10% PR+ versus 12%) but not in tumor size or grade. For cervical cancer higher proliferation rates have been suggested in low SES [START_REF] Symonds | Advanced-stage cervix cancer: rapid tumour growth rather than late diagnosis[END_REF], which could hold for breast cancer as well.

The presence of a socioeconomic gradient in breast cancer survival has been reported in previous studies [START_REF] Schrijvers | Socioeconomic variation in cancer survival in the southeastern Netherlands, 1980-1989[END_REF][START_REF] Gentil-Brevet | The influence of socioeconomic and surveillance characteristics on breast cancer survival: a French population-based study[END_REF][START_REF] Bastiaannet | Socioeconomic differences in survival among breast cancer patients in the Netherlands not explained by tumor size[END_REF][START_REF] Schrijvers | Cancer patient survival by socioeconomic status in seven countries: a review for six common cancer sites [corrected][END_REF] and our results show that this is, at least partly, related to screening attendance.

The crude 5-year survival rates we observed (respectively 89% and 76% for those who did and did not attend screening, i.e. RR 1.2) were fairly comparable to results reported in Sweden, where the age and stage adjusted relative risk of death was 1.4 for non-attenders [START_REF] Zackrisson | Non-attendance in breast cancer screening is associated with unfavourable socio-economic circumstances and advanced carcinoma[END_REF]. Moreover, the crude 5-year survival rates observed in our study (77% for patients with cancers not detected by screening versus 91% for those with screen-detected cancers) are comparable to the rates of 84% and 94% observed in a study performed in Northern Italy [START_REF] Cortesi | Prognosis of screendetected breast cancers: results of a population based study[END_REF]. Unfortunately, no SES-specific life tables were available to estimate breast cancer specific survival according to SES. Similar patterns to overall survival were observed when using general life tables, although this may lead to underestimation of the relative survival rates in low SES and overestimation in high SES.

In this study, Cox' regression has been applied to assess causality in socioeconomic inequalities in survival from breast cancer. This method requires several stringent assumptions to be satisfied and does not allow for interactions between exposure (SES) and mediators (stage and treatment) [START_REF] Kaufman | A further critique of the analytic strategy of adjusting for covariates to identify biologic mediation[END_REF].

Furthermore, for hazard ratios the decomposition into effects was stated not to be valid [START_REF] Kaufman | A further critique of the analytic strategy of adjusting for covariates to identify biologic mediation[END_REF]. To the best of our knowledge, there is no accessible better way to analyze mediation than via Cox' regression.

Although interpretation of effects from regression models should be guarded, these results suggest an effect of stage on survival differences for interval cancers and in non-attenders, while comorbidities affected survival in screen-detected patients. 10/20

23-1-2011

The socioeconomic differences in stage at diagnosis explained some of the socioeconomic inequalities in breast cancer survival. Stage distribution was only slightly different between the SES categories in screen-detected cancers, while differences were larger in patients who did not attend the screening and especially in interval cancers. In these latter two groups, stage indeed explained (part of) the socioeconomic differences. In three other studies in the UK and France socioeconomic inequalities in breast cancer survival were ascribed to stage [START_REF] Macleod | Socio-economic deprivation and stage of disease at presentation in women with breast cancer[END_REF][START_REF] Gentil-Brevet | The influence of socioeconomic and surveillance characteristics on breast cancer survival: a French population-based study[END_REF][START_REF] Kaffashian | Socioeconomic effects on breast cancer survival: proportion attributable to stage and morphology[END_REF]. However, in an older study from the UK, including patients diagnosed between 1980 and 1987, tumor stage or biology did not contribute to the socioeconomic gradient in breast cancer survival [START_REF] Carnon | Relation between socioeconomic deprivation and pathological prognostic factors in women with breast cancer[END_REF]. More recently, a study in the Netherlands on breast cancer patients diagnosed from 1995 to 2005 observed that 10-year relative survival rates were 79% in high SES compared to 74% in low SES, and the accompanying relative excess risk of dying from breast cancer was 1.19. This was after adjustment for (among others) grade, stage, nodal status, treatment [START_REF] Bastiaannet | Socioeconomic differences in survival among breast cancer patients in the Netherlands not explained by tumor size[END_REF]. Only one of the foreign studies took into account the role of breast cancer screening and compared the survival of cancers detected clinically with those detected in the screening program.

Survival inequalities were only present for stage 3 [START_REF] Gentil-Brevet | The influence of socioeconomic and surveillance characteristics on breast cancer survival: a French population-based study[END_REF].

Interventions to increase screening participation have been reviewed and distinguished into factors related to invitees, health-care providers, health-care context, and media and financial factors [START_REF] Weller | Uptake in cancer screening programmes[END_REF]. Most important to increase participation in the Netherlands will be the factors related to invitees, e.g. by timing of invitation, personal factors (perceived risk of cancer, perceived self-efficacy), customizing invitation to the individual needs (for example by telephone counseling), and address psychological mediators of cancer screening behavior [START_REF] Weller | Uptake in cancer screening programmes[END_REF].

A limitation of this study is the fact that we do not know the reasons of non-participation in 54% of the cases. To increase attendance rates, this should be studied. Comorbidity could explain (part of) the non-participation, as it was present at diagnosis in 42% of the women who did not compared to 37% in women who did attend. As stated earlier, we used an indicator of SES based on the postal code of a residential area and not on individual data on income, education, etc. Since this aggregate covers a relatively small geographical area (on average 17 households), it is likely to represent a reliable approximation of individual SES. Furthermore, routinely collected income tax data have been found to provide reliable estimates of household income [START_REF] Bos | Nationale gegevens over sociaal-economische sterfteverschillen op basis van informatie over kleine geografische eenheden[END_REF]. Previous studies in the Netherlands have proven that socioeconomic differences based on neighborhood data tend to reflect socioeconomic differences 11/20 23-1-2011 accurately at the individual level [START_REF] Bos | Nationale gegevens over sociaal-economische sterfteverschillen op basis van informatie over kleine geografische eenheden[END_REF][START_REF] Bos | De omvang van sociaal-economische verschillen gemeten op buurtniveau: vergelijking met schattingen op basis van informatie op individueel niveau[END_REF][START_REF] Smits | Effecten van sociaal-economische status van kleine, middelgrote en grote geografische eenheden op de sterfte[END_REF]. In addition, we defined non-participation in patients as women who did not attend the screening program within the last 2 years before diagnosis. In fact, 64% of these women indeed never attended, but 32% had attended more than 3 but less than 4 years before diagnosis, and 4% had attended the program more than 3 years before diagnosis. Despite these limitations, the results of this study form an important contribution to the limited information available on socioeconomic inequalities in screening attendance and the consequences in terms of stage at diagnosis and survival in the Netherlands. Moreover, in this large population-based study we included all women being eligible for breast cancer screening and all breast cancer patients.

In conclusion, despite the absence of financial barriers for participation in the Dutch mass screening program, socioeconomic inequalities in attendance rates remain present, resulting in a significantly worse tumor stage and lower survival rate for women with low SES. Therefore, these results underline the importance of increasing participation among women of all SES groups, with special attention to those with low SES. Women <50 were included as they are first invited in the year of their 50 th birthday. Some women aged >75 were included as they received their last invitation just before their 76 th birthday. 16/20

Figure 2 .Figure 3 .Figure 4 . 5 -

 2345 Figure 2. Attendance of breast cancer screening according to socioeconomic status in southern Netherlands 1998-2005.

Table 1 .

 1 Characteristics of women invited for mass breast cancer screening and multivariable analyses of the odds of attending the mass breast cancer screening in southern Netherlands

		Characteristics	Multivariable analyses
		Not attended	Attended	Odds of attending
		N %	N %	OR	(95%CI)
	Age
	<50	12586 8%	67768 8%	0.96	(0.9-1.0)
	50-54	34097 20%	190490 21%	1.00
	55-59	34533 21%	207443 23%	1.08	(1.1-1.1)
	60-64	27779 17%	169409 19%	1.13	(1.1-1.2)
	65-69	25886 16%	147179 16%	1.08	(1.1-1.0)
	70-75	27247 16%	108970 12%	0.73	(0.7-0.7)
	>75	4269 3%	10296 1%	0.31	(0.3-0.4)
	Year of invitation
	1998	19329 12%	95121 11%	1.00
	1999	20007 12%	100765 11%	1.09	(1.1-1.1)
	2000	21490 13%	113472 13%	1.11	(1.1-1.1)
	2001	20487 12%	103502 11%	1.09	(1.1-1.1)
	2002	22396 13%	123958 14%	1.15	(1.1-1.2)
	2003	19427 12%	114023 13%	1.26	(1.2-1.3)
	2004	23397 14%	132171 15%	1.16	(1.1-1.2)
	2005	19864 12%	118543 13%	1.27	(1.2-1.3)
	Socioeconomic status
	Low	54008 32%	201396 22%	1.00
	Intermediate	65015 39%	381152 42%	1.54	(1.5-1.6)
	High	47374 28%	319007 35%	1.75	(1.7-1.8)
	All values are adjusted for age, year of invitation and socioeconomic status. OR: odds ratio, 95% CI: 95%
	confidence interval. Values in bold are significant.

Table 2 .

 2 Hazard ratios of death from breast cancer according to screening attendance and the contribution of comorbidity and stage to socioeconomic differences § HR = Hazard Ratio, low versus high socioeconomic status. Values in bold are significant. Figure 1. Flow-chart of the invitations and attendance of breast cancer screening according to socioeconomic status. Int.: intermediate, interv: interval cancer, SD: screen-detected cancer, SES: socioeconomic status.

	23-1-2011

12/20 23-1-2011 Acknowledgement This work was supported by a grant from Bevolkings Onderzoek Borstkanker Zuid (which organizes the population-based screening for breast cancer in southern Netherlands). 13/20 23-1-2011

Conflict of interest statement

None declared.


Dr Martin Tepel
email: mtepel@health.sdu.dk

Alexandra Scholze

Igor W Blau

M.D. Arnold Ganser

Acute megakaryoblastic leukaemia AML FAB-M7 in a patient 15 years after kidney transplantation

Keywords: Kidney transplantation, leukaemia, AML FAB-M7, fever of unknown origin

Answers to Reviewer's comments 1. Molecular changes were not determined.

2. Because the patient presented severely disabled (Karnofsky score 30), the therapy was limited.

3. The immunosuppressive regimen consisted of cyclosporine A and prednisolone. The antihypertensive treatment comprised furosemide, a beta blocker and an ACE inhibitor. No episodes of acute rejection had occurred in the post-transplant course.

4.

A computed tomography of thorax and abdomen did not show pathological findings except enlargement of the spleen with 15 cm. Lymph node enlargement was not observed.

Transoesophageal echocardiography did not show signs of endocarditis. A broncho-alveolar lavage excluded pneumocystis carinii, mycobacteria or legionellae, and the patient was tested negative for human immunodeficiency virus and hepatitis. Screening for cytomegalovirus was negative, whereas polymerase chain reaction for Epstein-Barr virus was slightly positive. A bone marrow aspirate showed mainly myeloid cells with enhanced expression of cluster of differentiation 13 (CD 13), representing an early granulocytic antigen. On the other hand, CD 33, an antigen of myeloid progenitor cells, was observed in only 3%. The stemcell factor receptor c-kit, a marker of immature blast cells, was enhanced and could be detected in 4% of cells. A cytogenetic analysis showed no structural or clonal numerical chromosomal aberrations. The cytological picture showed an extensive megakaryopoiesis with a shift to early cell stages and partially atypical nuclei (Figure 1). Staining showed an excess of stored iron. The erythropoiesis/granulopoiesis (E/G) ratio was markedly shifted in favor of granulopoiesis. All specimens showed a population of megakaryocytic blast cells. Cytology of the bone marrow aspirate showed acute AML FAB-M7. Because the patient was severely disabled, a therapy with low dose cytarabine was started. However, the patient developed severe aplasia and septicemia. The patient died 3 weeks after diagnosis.

A wide variety of causes are considered when fever occurs in a patient after renal transplantation. The most common causes are viral, bacterial or opportunistic infections, transplantat rejection, side effects of new medications or malignancies [START_REF] Cohen | General health management and long-term care of the renal transplant recipient[END_REF]. It appears that AML does develop more frequently after transplantation than in the normal population [START_REF] Gorschlüter | Successful induction and consolidation therapy of acute myeloid leukaemia in a renal allograft recipient[END_REF][START_REF] Subar | Acute leukaemia following renal transplantation[END_REF][START_REF] Thalhammer-Scherrer | Post-transplant acute myeloid leukemia (PT-AML)[END_REF].

The incidence of AML after solid organ transplantations is about 0.2 to 2.5%. Post-transplant-AML seems to develop after a median interval of 5 years (range 1-17 years). It is heterogeneous with respect to FAB classification and may show chromosomal and molecular changes [START_REF] Thalhammer-Scherrer | Post-transplant acute myeloid leukemia (PT-AML)[END_REF]. However, the present case shows that AML FAB-M7 may develop as treatment related without carrying multiple chromosomal aberrations. French-American-British M7 (AML FAB-M7).

4 4 Figure legend Figure 1 .

 44legend1 Figure legend

  The patient had been transplanted with a cadaveric kidney 15 years earlier. The cause of end stage renal disease was unknown. No episodes of acute rejection had occurred in the post-transplant period. There was a slow progressive loss of renal function, a renal transplant biopsy obtained 1 year earlier showed a pronounced chronic allograft

	Manuscript
	Click here to download Manuscript: Scholze NTx Leukemia7 Ann Hematol Letter.doc	Click here to view linked References
			2
		Letter to the Editor Dear Editor
	1 1
	2 2
	3 4 3 4	Acute megakaryoblastic leukaemia FAB-M7 in a patient 15 years after kidney we report a case of acute megakaryoblastic leukaemia French-American-British classification
	5 6 5 6	transplantation M7 (AML FAB-M7), a rare form of leukaemia in the late post-transplantation period, which
	7 7	occurred in a patient 15 years after kidney transplantation. A 42-year-old man presented
	8 9 8 9	Alexandra Scholze 1 , Igor W. Blau 2 , Martin Tepel 1 severely disabled (Karnofsky score 30) with fever of unknown origin and pancytopenia. He
	10 11 10 11	complained of weakness, loss of appetite and elevated temperature for several days, ranging
	12 13 12 13	1 Odense University Hospital, Department of Nephrology, Odense, Denmark, from 38°C to 40°C.
	14 15 14 15	2 Charité Campus Benjamin Franklin, Department of Hematology, Oncology and Transfusion
	16 17 16 17	Medicine, Berlin, Germany.
	18 18
	19 19
	20 20	Word count 594 words
	21 21
	22 22
	23 23
	24 24
	25 26 25 26	Address for correspondence:
	27 28 27 28	Dr. Martin Tepel
	29 29	Odense University Hospital, Department of Nephrology
	30 30
	31 31	University of Southern Denmark, Institute of Molecular Medicine
	32 33 32 33	Winslowparken 21.3
	34 35 34 35	DK 5000 Odense C
	36 37 36 37	Denmark
	38 39 38 39	Fax. +45-6613-3479
	40 40	Email. mtepel@health.sdu.dk
	41 41
	42 42
	43 43
	44 44
	45 45
	46 46
	47 47
	48 48
	49 49
	50 50
	51 51
	52 52
	53 53
	54 54
	55 55
	56 56
	57 57
	58 58
	59 59
	60 60
	61 61
	62 62
	63 64 63 64		2
	65 65

nephropathy with a severe arteriolohyalinosis but no signs of acute rejection or calcineurin inhibitor toxicity. The immunosuppressive regimen consisted of prednisolone (10 mg/day) and cyclosporine A (200 mg/day) throughout. The antihypertensive treatment comprised furosemide, beta blockers and angiotensin converting enzyme inhibitor. White blood count was reduced to 1.83/nL consisting of 76% neutrophilic granulocytes, 11% lymphocytes 13 % monocytes 0% eosinophilic granulocytes and 0% basophilic granulocytes. Platelet count was reduced to 70/nL and hemoglobin was reduced to 7.0g/dL. The clinical evaluation of the skin, head and neck, heart and lung, abdomen including the side of transplantation, and the neurological status showed no pathological findings. Kidney function was stable with creatinine values of 400µmol/L. Urinanalysis did not show urinary tract infection. Blood cultures were negative. Ultrasound of the transplanted kidney showed no pathologic findings.

Scholze et al., Figure 1.


Wojciech Baran
email: wbaran@mp.pl

and cyclophosphamide in patient with B-cell chronic

Effective treatment of leukemia cutis with combination of rituximab, cladribine

Dear Editor B-cell chronic lymphocytic leukemia (B-CLL) is the most common adult leukemia in Western countries with annual incidence rate 3-5 cases per 100 000 [START_REF] Robak | Skin lesions in chronic lymphocytic leukemia[END_REF]. Skin lesions in patients with CLL may represent nonspecific manifestations related to the impaired immune system or specific skin involvement, known as leukemia cutis (LC). The presence of LC varies from the type of leukemia, but in patients with B-CLL is far less common comparing to T-cell leukemia [START_REF] Robak | Skin lesions in chronic lymphocytic leukemia[END_REF][START_REF] Agnew | Cutaneous findings in chronic lymphocytic leukaemia[END_REF]. The limited literature [START_REF] Agnew | Cutaneous findings in chronic lymphocytic leukaemia[END_REF][START_REF] Ali | Subclinical chronic lymphocytic leukemia with atypical cutaneous presentation[END_REF][START_REF] Cerroni | Specific cutaneous infiltrates of B-cell chronic lymphocytic leukemia: a clinicopathologic and prognostic study of 42 patients[END_REF][START_REF] Plaza | Unusual cutaneous manifestations of B-cell chronic lymphocytic leukemia[END_REF][START_REF] Khandelwal | Subclinical chronic lymphocytic leukaemia associated with a 13q deletion presenting initially in the skin: apropos of a case[END_REF][START_REF] Ural | Oral fludarabine treatment of cutaneous infiltration in a patient with B-cell chronic lymphocytic leukaemia[END_REF][START_REF] Anyfantakis | Efficacy of intralesional methotrexate in specific cutaneous involvement of B-cell chronic lymphocytic leukaemia[END_REF] shows that LC usually appears later in the course of the disease, after the symptoms of fatigue, night sweats, weight loss, easy bruising, heapatosplenomegaly and enlarged lymph nodes. Solitary skin lesions manifesting as papules, plaques, nodules, tumours, more rarely as vesicobullous lesions, erythoderma or paronychia may mimic other, benign skin disorders [START_REF] Robak | Skin lesions in chronic lymphocytic leukemia[END_REF][START_REF] Anyfantakis | Efficacy of intralesional methotrexate in specific cutaneous involvement of B-cell chronic lymphocytic leukaemia[END_REF]

  Figure a. Numerous teleangiectatic papules.

Figure b .

 b Figure b. After 2 cycles of CCR regimen, all lesions almost completely resolved.

Figure c .

 c Figure c. Multiple nodules on the arm.

Figure d .

 d Figure d. After 2 cycles of CCR regimen, all lesions almost completely resolved.


Dr Frederik Damm
email: damm.frederik@mh-hannover.de

Birgit Markus

Felicitas Thol

Michael Heuser

Arnold Ganser

Jürgen Krauter

Genetic changes of miR-182 G106A: rather a polymorphism than a somatic mutation

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Damm et al.

Genetic changes of miR-182 2 syndrome (MDS) and acute myeloid leukemia (AML). The association of -7/7q-with myeloid leukemia suggests that these regions contain novel tumor suppressor gene(s) whose loss of function contributes to leukemic transformation or tumor progression. Based on chromosome banding analysis, two critical regions have been identified: one in band 7q22 and a second in bands 7q32-q35 [START_REF] Fischer | Molecular cytogenetic delineation of deletions and translocations involving chromosome band 7q22 in myeloid leukemias[END_REF] . Molecular analyses of these two regions led to the identification of mutations in the EZH2 gene in MDS [START_REF] Nikoloski | Somatic mutations of the histone methyltransferase gene EZH2 in myelodysplastic syndromes[END_REF][START_REF] Ernst | Inactivating mutations of the histone methyltransferase gene EZH2 in myeloid disorders[END_REF] . Furthermore, high expression levels of the histone methyltransferase MLL5, located on chromosome 7q22, were reported to be associated with favorable prognosis in AML [START_REF] Damm | Prognostic importance of histone methyltransferase Mixed Lineage Leukemia 5 (MLL5) expression in acute myeloid leukemia[END_REF] . Searching for further genes located in this specified region we found the article by Watkins et al on the mutational screening of microRNAs in splenic marginal zone lymphoma (SMZL) [START_REF] Watkins | Characterisation of 7q32 deletion of splenic marginal zone lymphoma demonstrates frequent miR-182 somatic mutations in a wide range of lymphoma subtypes[END_REF] . Sequencing of microRNAs clustering in the minimally deleted region of 7q32 revealed a recurrent genetic aberration of the miR-182 affecting 22% of 60 analysed SMZL cases. In all of these cases a G to A substitution at nucleotide position 106 of the pri-miRNA was reported. Nucleotide position 106 was postulated to be important for DGCR8 binding and subsequent accurate Drosha cleavage but is not located in the seed sequence of mature miR182 or in the miR182* sequence [START_REF] Watkins | Characterisation of 7q32 deletion of splenic marginal zone lymphoma demonstrates frequent miR-182 somatic mutations in a wide range of lymphoma subtypes[END_REF] . Furthermore, Watkins et al screened a large cohort of different lymphoma types and found this genetic change with different frequencies ranging from 0-22% in various other lymphomas [START_REF] Watkins | Characterisation of 7q32 deletion of splenic marginal zone lymphoma demonstrates frequent miR-182 somatic mutations in a wide range of lymphoma subtypes[END_REF] .

We sought to establish whether miR-182 alterations identified in SMZL could also be present in AML. For this purpose, we sequenced the primary miRNA for mature miR-182 in 109 AML patients. Mutation screening was performed with primers and PCR conditions as described in the work of Watkins et al [START_REF] Watkins | Characterisation of 7q32 deletion of splenic marginal zone lymphoma demonstrates frequent miR-182 somatic mutations in a wide range of lymphoma subtypes[END_REF] . All 109 patients were enrolled on the AML SHG 0199 trail (ClinicalTrials Identifier NCT00209833). All patients received intensive, response-adapted double induction and consolidation therapy as previously described [START_REF] Damm | Single Nucleotide Polymorphism in the Mutational Hotspot of WT1 Predicts a Favorable Outcome in Patients With Cytogenetically Normal Acute Myeloid Leukemia[END_REF][START_REF] Wagner | Impact of IDH1 R132 mutations and an IDH1 single nucleotide polymorphism in cytogenetically normal acute myeloid leukemia: SNP rs11554137 is an adverse prognostic factor[END_REF] . Alteration of the nucleotide at position 106 with a G to A Damm et al.

Genetic changes of miR-182 3 substitution (G106A) was found in 15% (16 of 109) of the patients (Figure 1A). The same G106A alteration was previously reported as a somatic mutation [START_REF] Watkins | Characterisation of 7q32 deletion of splenic marginal zone lymphoma demonstrates frequent miR-182 somatic mutations in a wide range of lymphoma subtypes[END_REF] . Furthermore, we identified another G to A substitution at position 94 in two of the 109 AML patients. No difference in treatment response or patient outcome was observed between patients with the miR-182 G106A substitution (n=16) compared to patients without this alteration (n=93; complete remission rate: 67% vs. 71%, p=.73; relapsefree survival: p=.78, and overall survival: p=.14). In three of the 16 patients with the G106A variation we were able to analyse serial follow-up bone marrow or peripheral blood samples. All three patients were in complete remission (CR) from their AML at the time point of follow-up analysis. Surprisingly, in all three patients, the G106A variation was detected in at least 2 available follow-up samples of each patient.

These results suggest that the G106A variation is not a mutation but a polymorphism instead. To verify this hypothesis, we screened a series of 63 healthy blood donors for the presence of the miR-182 G106A alteration. In 12 of the 63 controls (19%) the miR-182 G106A variation was detected (Figure 1B). One healthy control even showed a homozygous G to A substitution (Figure 1C), confirming that we are indeed dealing with a common population polymorphism rather than a somatically acquired mutation. Also the other observed G94A variant was detected in one healthy control.

Watkins et al called the miR-182 G106A variant a somatic mutation as they detected this alteration only in tumour but not in normal tissue from a small, exemplary series of their affected lymphoma patients [START_REF] Watkins | Characterisation of 7q32 deletion of splenic marginal zone lymphoma demonstrates frequent miR-182 somatic mutations in a wide range of lymphoma subtypes[END_REF] . Our analysis in healthy controls underlines the importance of a disease-free population cohort when classifying genetic alterations as either mutations or polymorphisms. Similar findings for other gene variations led to a re-evaluation of the assumed pathogenic role in the last years 8,9 .

Figure Legend

Figure 1 :

 1 Figure 1: Representative sequence traces for the miR-182 G106A substitution of (A) an AML patient, (B) a healthy blood donor and (C) a healthy blood donor with a homozygous miR-182 G106A substitution. The arrows are indicating the miR-182 G106A substitution o n t h e lef t and a single nucleotide polymorphism in the intronic region o n t h e r ig h t . MiR-182 nucleotide numbering uses the first base of the primary miRNA for mature miR-182 as nucleotide _1 on the basis of National Center for Biotechnology Information sequence NR_029614.1.

This study was supported by the Hannelore-Munke Fellowship and the HiLF grant 2010 awarded to F.D.


Daniele Massera

Friedrich Mittermayer

Bettina Gisslinger

Damla Olcaydu

Michael Wolzt

Heinz Gisslinger
email: heinz.gisslinger@meduniwien.ac.at

Asymmetric dimethylarginine levels in essential thrombocythemia-a retrospective analysis

come

Dear Editor, Arterial and venous thromboembolic events are the major cause of morbidity and mortality in essential thrombocythemia (ET). Risk stratification is indispensable for choosing the appropriate patient-selective therapy [START_REF] Tefferi | Classification and diagnosis of myeloproliferative neoplasms: The 2008 world health organization criteria and point-of-care diagnostic algorithms[END_REF]. Established risk factors for cardiovascular events are age above 60 years and a history of thromboembolic events [START_REF] Cortelazzo | Incidence and risk factors for thrombotic complications in a historical cohort of 100 patients with essential thrombocythemia[END_REF]. In selected patients, genetic polymorphisms (Factor V Leiden, prothrombin G20210A mutation) and acquired risk factors for thrombophilia (homocysteinemia, antiphospholipid antibodies) have been described to increase the risk for thrombosis [START_REF] Harrison | Patients with essential thrombocythaemia have an increased prevalence of antiphospholipid antibodies which may be associated with thrombosis[END_REF][START_REF] Gisslinger | Mutation of the prothrombin gene and thrombotic events in patients with polycythemia vera or essential thrombocythemia: A cohort study[END_REF][START_REF] Gisslinger | Homocysteine levels in polycythaemia vera and essential thrombocythaemia[END_REF][START_REF] Ruggeri | Factor v leiden mutation carriership and venous thromboembolism in polycythemia vera and essential thrombocythemia[END_REF]. Currently, the JAK2-V617F mutation [START_REF] Lussana | Association of v617f jak2 mutation with the risk of thrombosis among patients with essential thrombocythaemia or idiopathic myelofibrosis: A systematic review[END_REF] and an elevated white blood cell count [START_REF] Carobbio | Leukocytosis is a risk factor for thrombosis in essential thrombocythemia: Interaction with treatment, standard risk factors, and jak2 mutation status[END_REF] are considered as additional risk factors for thrombosis. However, the pathogenesis for thrombosis in these patients is still unknown. Since levels of asymmetric dimethylarginine (ADMA) are elevated in patients with cardiovascular disease and predict cardiovascular morbidity and mortality [START_REF] Kielstein | Asymmetric dimethylarginine plasma concentrations differ in patients with endstage renal disease: Relationship to treatment method and atherosclerotic disease[END_REF], we speculated that ADMA elevation could play a role in the pathogenesis of thrombosis in ET.

The objective of this study was to investigate ADMA levels in 91 patients with ET as compared to 57 healthy individuals and to study the association between ADMA and other clinical parameters (complete blood cell count, JAK2-V617F mutation status, body mass index, smoking history, diabetes and hypertension, history of arterial and venous thrombosis).

For determination of ADMA levels, venous blood samples were collected at diagnosis, plasma separated and stored at -70°C. Analysis was performed by high-performance liquid chromatography as described previously [START_REF] Teerlink | Determination of arginine, asymmetric dimethylarginine, and symmetric dimethylarginine in human plasma and other biological samples by high-performance liquid chromatography[END_REF][START_REF] Mittermayer | Acute escherichia coli endotoxaemia decreases the plasma l-arginine/asymmetrical dimethylarginine ratio in humans[END_REF]. The coefficients of variation for inter-and intra-assay variation for this method were <3% for all analytes. The detection limit for methylarginines was 0.04 µmol/L. ADMA plasma concentrations were significantly higher in the patient cohort than in the control group. Mean ADMA concentration in the patient cohort was 1.01 µmol/L (SD = 0.49; 95% CI: 0.91 -1.11) compared to 0.48 µmol/L (SD = 0.11; 95% CI: 0.45 -0.51) in the control group (p<0.001). Additionally, we found a statistically significant correlation of ADMA with the platelet count (r = 0.312; p = 0.004). Since age cannot be excluded as a determinant of high ADMA levels and was also associated with the frequency of thrombotic events in previous studies [START_REF] Neunteufl | Endothelial dysfunction in patients with polycythaemia vera[END_REF], we performed a correlation analysis of ADMA levels and age, which showed no association. Furthermore, no correlation between ADMA and laboratory parameters other than the platelet count could be found (Table ). ADMA levels were also not influenced by the history of arterial or venous cardiovascular events. These findings could be a sign that ADMA is not a player in the pathogenesis of thrombosis in ET. Otherwise they might be caused by other factors: firstly, the limited number of patients included in this study may be insufficient to reveal a statistically significant association. Secondly, the determination of ADMA levels at a single time point -the time of diagnosis -might not be sufficient to show an increase in the risk for thrombotic events during the natural disease course of ET. Finally, other yet unknown risk factors might have a greater influence on the thrombotic tendency in ET patients than ADMA.

Elevations of ADMA levels have been described in several diseases, in some of which it has been shown to be an important surrogate parameter for survival. Our study demonstrates that ET has to be added to the list of disorders with elevated ADMA levels.

However, the clinical importance of elevated ADMA levels in ET needs to be established in studies with larger patient cohorts.

KEYWORDS

essential thrombocythemia, myeloproliferative neoplasms, asymmetric dimethylarginine,

Table

  Correlation of age, BMI and blood parameters with ADMA; r = Pearson correlation coefficient

	Clinical parameters	Mean (SD)	r	p
	age (years) [median-range]	53.96 (20.96 -85.50)	0.074	0.483
	BMI (kg/m 2 )	24.8 (3.49)	0.017	0.887
	white blood cell count (×10 9 /L)	9.3 (3.0)	0.178	0.120
	red blood cell count (×10 12 /L)	4.8 (4.8)	0.154	0.177
	hemoglobin (g/dL)	13.8 (1.4)	0.134	0.249
	hematocrit (%)	41.3 (4.3)	0.188	0.101
	platelet count (×10 9 /L)	964.6 (370.9)	0.312	0.004