Impact of COVID-19 on breast cancer screening: time series analysis of pre-pandemic, pandemic and post-pandemic periods

OBJECTIVES: This study aimed to evaluate the impact of the COVID-19 pandemic on breast cancer screening activity, cancer detection rates, and stage at diagnosis by comparing pre-pandemic, pandemic, and post-pandemic periods. METHODS: This retrospective cross-sectional study included women who underwent breast cancer screening between March 2018 and February 2024. The study period was divided into three phases: pre-pandemic (March 2018 - February 2020), pandemic (March 2020 - February 2022), and post-pandemic (March 2022 - February 2024). Screening activity, including mammography and breast ultrasonography examinations, cancer detection rates, age at diagnosis, tumour size, and stage distributions were evaluated. RESULTS: A total of 102,833 women underwent breast cancer screening during the study period. Significant differences were observed in the numbers of screened women, mammography examinations, ultrasound examinations, and breast cancers detected across the study periods (all p < 0.001). The cancer detection rate increased from 10.64 per 1,000 screened women in the pre-pandemic period to 12.68 during the pandemic and 16.32 in the post-pandemic period (p < 0.001). Early-stage diagnoses decreased from 84% to 72%, whereas advanced-stage diagnoses increased from 16% to 28% (p = 0.002). The proportion of metastatic disease increased from 5.6% to 22% (p = 0.028). No significant differences were observed in age at diagnosis (p = 0.896), tumour size (p = 0.201), or T stage distribution (p = 0.519). CONCLUSIONS: The COVID-19 pandemic substantially affected breast cancer screening and diagnosis. Although screening activity declined during the pandemic, cancer detection rates increased and a significant shift toward advanced-stage and metastatic disease was observed in the post-pandemic period. Maintaining resilient and accessible breast cancer screening services during future healthcare crises is essential to minimize diagnostic delays and improve patient outcomes.