[Changes in therapy for breast cancer patients as a result of mammography screening. An analysis of Bavarian cancer registry data from 2000 to 2008]

Abstract

Purpose: A quality controlled mammography screening programme was initiated at the end of 2003 in Bavaria, a region with 12.5 million inhabitants, and transferred over to the national screening programme at the end of 2006. The purpose of this study was to evaluate immediate population-based consequences of mammography screening on breast cancer therapy.

Methods: Data from 75 475 breast cancer cases, diagnosed between 2000 and 2008 and registered in one of the 6 Bavarian clinical cancer registries were analysed. 51.4% of these patients were between 50 and 69 years of age and therefore the target population for screening. Trends of prognostic factors and standard therapies were calculated for 3 age groups (≤49 years, 50-69 years, ≥70 years) by means of annual percentages as well as 95%-confidence intervals for the percent difference between 2000 and 2008 (year of diagnosis). For interpretation of therapy trends, logistic regression models were calculated.

Results: Therapy trends showed that the increasingly favourable stage distribution may have resulted in the reduction of more radical surgical methods such as mastectomy (2000: 32.6%; 2008: 19.6%) or axillary dissection (89.0% vs. 37.0%), especially for women aged 50-69. An increase of radiation therapies (59.7% vs. 66.6%) can be explained to some extent by the increase in breast conserving surgeries. The shift to more favourable prognostic factors led, in accordance with the guidelines, to an increase of the proportion of singular endocrine therapies (28.5% vs. 40.7%), a decrease of chemotherapies (20.4% vs. 13.1%) and therefore to more gentle systemic therapies overall. These trends strengthened in the years following the introduction of screening, with a simultaneous rise of screening participants in the target population.

Conclusion: The introduction of mammography screening in Bavaria has already shown the expected trend towards more favourable prognostic factors. Among other things, this could be a reason for the increasing use of more gentle therapies. Whether the screening in Bavaria leads to a mortality reduction, has to be analysed on the basis of an initial comparison of participation status followed by the trends in mortality thereafter.