Cancer Frequency in the Samtgemeinde Asse Statement by the German Commission on Radiological Protection
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Strahlenschutzkommission Geschäftsstelle der Strahlenschutzkommission Postfach 12 06 29 D-53048 Bonn http://www.ssk.de Cancer Frequency in the Samtgemeinde Asse Statement by the German Commission on Radiological Protection Adopted at the 260th meeting of the German Commission on Radiological Protection on 28 February/1 March 2013 The German original of this English translation was published in 2013 by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety under the title: Krebshäufigkeit in der Samtgemeinde Asse Stellungnahme der Strahlenschutzkommission This translation is for informational purposes only, and is not a substitute for the official statement. The original version of the statement, published on www.ssk.de, is the only definitive and official version. Cancer frequency in the Samtgemeinde Asse 3 Contents 1 Background ......................................................................................................... 4 2 Epidemiological findings ..................................................................................... 4 3 Statistical analysis of regional differences .......................................................... 7 4 Risk factors for leukaemia and thyroid cancer .................................................... 8 4.1 Leukaemia .................................................................................................. 8 4.2 Thyroid cancer ............................................................................................ 9 5 Exposure of the population to radiation as a result of release of radioactive substances from the Asse II mine ....................................................................... 9 6 The radiation exposure needed to explain the observed increases .................. 12 7 Summing up and position statement ................................................................. 13 References ................................................................................................................ 14 Cancer frequency in the Samtgemeinde Asse 4 1 Background A special analysis carried out by the Epidemiological Cancer Register of Niedersachsen (Epidemiologisches Krebsregister Niedersachsen, EKN) in response to an enquiry from the district (Landkreis) of Wolfenbüttel about the incidence of cancer in the municipal confederation (Samtgemeinde) Asse showed that between 2002 and 2009 there were significantly more new cases of leukaemia and thyroid cancer than would have been expected by comparison with the rest of the district of Wolfenbüttel (excluding the Samtgemeinde Asse) (EKN 2010a). The reason for the EKN’s analysis of Samtgemeinde Asse and the district of Wolfenbüttel was: “The background to this special analysis is an enquiry by the district of Wolfenbüttel to the Epidemiological Cancer Register of Niedersachsen (EKN) in 2008 regarding the frequency of leukaemias in the Samtgemeinde Asse. At that time there was insufficient data available and leukaemias and lymphomas were significantly under-recorded; small-scale analysis was not therefore possible. There is now sufficient data for the analysis to be carried out. The results of the analysis are presented in this report.” (EKN 2010a). The query thus related solely to leukaemias and the Samtgemeinde Asse. The EKN’s analysis of the incidence of leukaemia was therefore hypothesis-led; for other cancers and other municipalities in the former administrative district of Braunschweig, exploratory analysis was undertaken in (EKN 2010a) and later in (EKN 2010b). All distinctions between men and women were likewise exploratory. In view of the large number of tests carried out, it was necessary for a correction for multiple testing to be applied to significant results. Following the publication of (EKN 2010a), members of the state parliament and representatives of the district of Wolfenbüttel asked whether other municipalities in the district also had elevated cancer rates. In response the EKN conducted a supplementary analysis of all 41 reported diagnoses of cancer (EKN 2010b). The EKN established in (EKN 2010b) that after correction for multiple testing the results for all the municipalities of the district of Wolfenbüttel other than the Samtgemeinde Asse were not significant. The only significant findings were the results for leukaemia and thyroid cancer in the Samtgemeinde Asse. The Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) wrote to the Commission on Radiological Protection (SSK) on 20 December 2010 requesting a statement on the results of the EKN’s analysis of the incidence of cancer in the Samtgemeinde Asse. In particular, the statement needed to examine the statistical methods used and answer the following questions: Is there radiobiological information that could plausibly explain the findings? How can the findings be explained? 2 Epidemiological findings The SSK has examined whether the EKN’s analysis conforms with good epidemiological practice and whether the findings are transparent and reliable. The SSK is of the view that the EKN’s analysis of the issue of a regional cancer cluster in the district of Wolfenbüttel was correctly carried out. The conclusions are likewise correct. The SSK asked the EKN to go beyond the published analyses (EKN 2010a, 2010b) and conduct a similar analysis of the data from the SG Asse using the former administrative district of Braunschweig as a comparison region. The larger population in the former administrative district of Braunschweig permits a more robust analysis. The SSK has also taken this analysis into account in its statement. Cancer frequency in the Samtgemeinde Asse 5 In (EKN 2010a) the EKN’s hypothesis-led analysis of cancer frequency in the Samtgemeinde Asse by comparison with the district of Wolfenbüttel excluding the Samtgemeinde Asse revealed a significant increase in the standard incidence ratio (SIR) for cases of leukaemia (ICD10 C91C95) (Table 1). Gender-differentiated analysis yielded different SIR values for men and women. This is based on 18 new cases recorded in the period 2002 until 2009 (males: 12; females: 6) by comparison with the expected number of 8.5 cases (males: 5.2, females: 3.3). In (EKN 2010a) the EKN’s exploratory analysis of cancer frequency in the Samtgemeinde Asse by comparison with the district of Wolfenbüttel excluding the Samtgemeinde Asse revealed a significant increase in the standard incidence ratio for thyroid cancer (ICD10 C73) in women (Table 2). Gender-differentiated analysis yielded different SIR values for men and women. This is based on 12 new cases recorded in the period 2002 until 2009 (males: 2, female: 10) by comparison with the expected number of 3.9 cases (males. 0.6, females: 3.3). Using the former administrative district of Braunschweig as a comparison region, the EKN again found a significantly elevated SIR for leukaemia in the Samtgemeinde Asse (Table 1). Here, too, gender-differentiated analysis yielded different SIR values for men and women. This is based on 18 new cases recorded in the period 2002 until 2009 (males: 12, females: 6) by comparison with the expected number of 8.3 cases (males: 4.8, females: 3.5). Using the former administrative district of Braunschweig as a comparison region, the EKN also found a significantly elevated SIR for thyroid cancer in the Samtgemeinde Asse (Table 2), although this was not significant at the 5 % level for 41 tests corrected for multiple testing. Gender-differentiated analysis again yielded different SIR values for men and women. This is based on 12 new cases recorded in the period 2002 until 2009 (males: 2, females: 10) by comparison with the expected number of 4.7 cases (males: 1.3, females: 3.4). Table 1: SIR of leukaemia in the Samtgmeinde Asse (compared to the district of Wolfenbüttel excluding the Samtgemeinde Asse (EKN 2010a) and the district of Braunschweig(EKN 2011)). The row shaded grey was the result of an external enquiry; the confidence interval (CI) can therefore be regarded as hypothesis-led. All the other findings should be regarded as exploratory. SIR 95% CI Total 2.12 1.253.35 Comparison region: district of Wolfenbüttel Men 2.33 1.204.06 excl. the Samtgemeinde Asse Women 1.80 0.663.91 Total 2.17 1.283.43 Comparison region: former administrative Men 2.49 1.294.35 district of Braunschweig Women 1.72 0.633.74 Cancer frequency in the Samtgemeinde Asse 6 Table 2: SIR of thyroid cancer in the SG Samtgmeinde Asse (compared to the district of Wolfenbüttel excluding the Samtgemeinde Asse (EKN 2010a) and the district of Braunschweig(EKN 2011)). All the findings should be regarded as exploratory. SIR 95% CI Total 3.05 1.585.33 Comparison region: district of Men 3.36 0.3812.13 Wolfenbüttel excl. the Samtgemeinde Asse Women 3.00 1.435.51 Total 2.55 1.324.46 Comparison region: former administrative Men 1.56 0.185.56 district of Braunschweig Women 2.94 1.415.40 The SSK is of the view that of the two available analyses of the Samtgemeinde Asse – one by comparison with the district of Wolfenbüttel (excluding the Samtgemeinde Asse) and the other by comparison with the former administrative district of Braunschweig – the calculations by comparison with the former administrative district of Braunschweig should be used for analysis, since they are based on a larger data set. It is possible that the district of Wolfenbüttel’s enquiry to the EKN was made not without cause but as the result of a concrete suspicion. This is supported by the fact that, of the two municipal confederations (Samtgemeinde