Evaluation of recall rates in the Irish national breast screening programme: Insights from two million screening mammograms

Background: Breast cancer screening aims to reduce breast cancer mortality and morbidity through early detection and treatment. Recall rate is a key performance indicator of population-based breast screening, representing the proportion of women recalled for further evaluation. Guidance on acceptable recall rates vary internationally. Aim: To examine recall patterns and characteristics within the population-based breast screening programme in Ireland. Methods: An anonymous aggregate retrospective study of 2,031,995 mammography screening examination results, was conducted between 2000 and 2019. Descriptive patterns of recall rates and characteristics were examined and stratified by prevalent and incident examinations. Differences across the time-periods (2000–2008, 2009–2017 and 2018–2019) were assessed using Chi-square tests. Results: Recall rate for screening examinations conducted during the full study period was 4.05 % (n = 82,338/2,031,995). Across three time-periods examined, recall rates among the prevalent screening examination group, increased, from 5.5 % to 8.0 % to 10.0 % and within the incident group from 2.3 % to 2.8 % to 3.0 %. Recalls due to calcifications and asymmetry increased over the time periods, most notably within the prevalent examinations where recalls due to calcification increased from 6.0/1,000 to 9.0/1,000 to 13.4/1,000 (p < 0.001), whilst recalls due to asymmetry increased from 17.1/1,000 to 31.3/1,000 to 41.0/1,000 (p < 0.001). Overall, among both prevalent and incident screening examinations, an increase in the cancer detection rate (CDR) was observed (p = 0.005 and p < 0.001 respectively). However, the overall positive predictive value (PPV) remained relatively stable. Conclusion: This study highlights the upward trajectory of recall within Ireland's national breast screening service. The findings highlight the need for discussions among a diverse range of stakeholders, including national and international screening networks, to determine the optimal recall rate to ensure the benefits of screening are maximised and all potential harms are minimised.