Prognostic factors and outcomes in women with breast cancer in Slovenia in relation to step-wise implementation of organized screening.

Introduction: The aim of organized breast cancer screening is early detection and reduction in mortality. Organized screening should promote equal access and reduce socio-economic inequalities. In Slovenia, organized breast cancer screening achieved complete coverage in 11-years' time. We explored whether step-wise implementation reflects in prognostic factors (earlier diagnosis and treatment) and survival of breast cancer patients in our population.

Methods: Using population-based cancer registry and screening registry data on breast cancer cases from 2008-2018, we compared stage distribution and mean time to surgical treatment in (A) women who underwent at least one mammography in the organized screening programme, women who received at least one invitation but did not undergo mammography and women who did not receive any screening invitation, and in (B) women who were invited to organized screening and those who were not. We also compared net survival by stage in different groups of women according to their screening programme status.

Results: Women who underwent at least one mammography in organized screening had lower disease stage at diagnosis. Time-to-treatment analysis showed mean time to surgery was shortest in women not included in organized screening (all stages = 36.0 days vs. 40.3 days in women included in organized screening). This could be due to quality assurance protocols with an obligatory multidisciplinary approach within the organized screening vs. standard treatment pathways which can vary in different (smaller) hospitals. Higher standard of care in screening is reflected in better survival in women included in organized screening (5-years net survival for regional stage: at least one mammography in the screening programme- 96%; invitation, but no mammography- 87.4%; no invitation or mammography in the screening programme- 82.6%).

Conclusion: Our study, which is one of the first in central European countries, shows that introduction of organized screening has temporary effects on population cancer burden indicators already during roll-out period, which should therefore be as short as possible.