Introduction: Before the country-wide introduction of mammography screening, testing of the organised screening took place in Weser-Ems, Bremen and Wiesbaden. Important quality assurance parameters (carcinomas detected during checkup intervals, tumour stage distribution, breast cancer incidence rate, breast cancer mortality rate) are to be evaluated via epidemiological cancer registries. For the model region Weser-Ems (MSWE) the record linkage with the epidemiological cancer registry Lower Saxony (EKN) was successfully accomplished. The technical realisation and first comparison analyses for the development of breast cancer incidence and of tumour size are reported.
Material and methods: The target population of the MSWE was 22,600 women aged 50-69 years. They were invited since May 2002 to mammography screening with a screening interval of two years. The record linkage of 12,913 women who participated until February 2004 in the MSWE, was realised by the use of the control number system of the epidemiological cancer registries. The observation time was between 6 and 25 month (median: 15 month). Reference population for comparison analyses were all women between 50 and 69 years of the remaining governmental district Weser-Ems (255,000 women).
Results: In the first record linkage 96 screening-cases (ICD-10 C50 + D05) could be identified. Additionally six interval cancers were determined (time between screening and diagnosis in months: median 5.5; mean 7.7). The breast cancer incidence increased in the MSWE area and in the control-area, the rise in the MSWE area being higher. The increase was especially observed with the small tumours. Women with breast cancer diagnosed by screening: 19.8% in-situ-cancer and 18.8% very small tumours < = 10 mm. In the control area Weser-Ems this rate with 5.6% in-situ-cancer and 14.5% very small tumours, was relatively high, indicating the spread of opportunistic mammographies in absence of organised screening.
Conclusion: First effects of mammography screening can be evaluated early by comparison between screening data and the data of population-based cancer registries. Using the control number system of the epidemiological cancer registries and comparison by pseudonyms the evaluation of quality assurance parameters of the MSWE can be realised in compliance with the data security law. The feedback of cancers, detected during checkup intervals is not covered by the cancer registry law. For the implementation of the guidelines for early recognition cancer legal adjustments will be necessary. This concept can be easily adapted to other screening programme.