Coverage of mammography imaging in and outside an organized breast cancer screening program - variation by age and sociodemographic groups.

Introduction: In recent decades, attendance to organized breast cancer screening has been decreasing in European countries. This could be partly due to an increase in the use of opportunistic screening. The aim of this study was to assess the coverage of imaging in and outside the screening program in Finland during the period of 1999-2018. We also compared the usage of imaging services across sociodemographic groups in the more recent years (2017-2018).

Methods: Our initial data consisted of 1,159,000 screening-target-aged women (50-69 years) in 1999-2018 and 1,849,000 women aged 30-89 years in 2017-2018. Data on organized breast cancer screening program was drawn from the Finnish Cancer Registry and supplemented with comprehensive individual data on mammograms and ultrasounds performed outside the program.

Results: Among the screening-aged women (50-69), a clear decline in the overall imaging coverage was observed during the study period (from 89 to 85%). The use of outside imaging increased slightly but not enough to compensate for the overall decrease. There were large differences in coverages between sociodemographic groups. Compared to manual workers and the unemployed, upper-level employees were around two times more active in using outside imaging (8.2% vs. 3.6% and 4.3%, respectively).

Interpretation: Overall breast imaging coverage has slowly decreased during the 2000s, while outside imaging has increased slightly. The coverage of imaging in and outside the program largely followed the same trends, with the highest usage concentrating on higher socioeconomical groups, native speakers and highly educated women.