Persistent Advanced Stage Migration in Breast Cancer Following COVID-19 Screening Disruptions: A 6-Year Population-Based Surveillance Study in Southern Brazil

PURPOSE This study evaluated the long-term impact of COVID-19 screening disruptions on breast cancer stage at diagnosis in Southern Brazil. Investigation focused on whether record screening volume in 2023 mitigated the pandemic-induced shift toward more advanced-stage disease. This analysis is critical for understanding health system resilience and the long-term effectiveness of cancer control programs in middle-income settings undergoing epidemiological transitions. METHODS A retrospective population-based study utilized secondary data from DATASUS and IBGE. Women aged 50-69 diagnosed between 2018 and 2023 were included. Stage-specific adjusted rates were calculated per 100,000 annual mammograms. Temporal trends in mammography volume and stage distribution were evaluated across pre-pandemic (2018-2019), pandemic (2020-2021), and post-pandemic (2022-2023) periods using surveillance data. Differences between periods were assessed using chi-square tests ( P < .05). Statistical modeling ensured that fluctuations in screening accessibility were properly normalized across the distinct biennial comparison periods. RESULTS Screening volume was stable before the pandemic (437,657 exams in 2018; 457,268 in 2019). In 2020, mammography volume plummeted 40.2% (273,166 exams). This disruption was accompanied by increased adjusted diagnosis rates for stage II (+58.7%), stage III (+63.9%), and stage IV (+63.5%). While partial recovery occurred in 2021, advanced-stage rates remained elevated. Screening volume normalized in 2022 and reached a series peak in 2023 with 497,817 mammograms. However, despite this record volume, stage III and IV diagnosis rates in 2023 remained 23% to 25% higher than baseline values. Record screening capacity alone was insufficient. A persistent “stage shift” exists where screening yield is dominated by late-stage presentations. This suggests that biological tumor progression during the diagnostic interruption now outpaces the system's ability to effectively clear the accumulated disease burden. CONCLUSION The COVID-19 pandemic induced a sustained shift toward advanced-stage breast cancer in Southern Brazil. Stage III and IV disease remained prevalent even after screening volume hit record levels in 2023. Findings reinforce the need for resilient surveillance systems in Low- and Middle-Income Countries (LMICs). “Catch-up” strategies must prioritize clearing the diagnostic backlog to prevent rising cancer mortality and ensure that future crises do not exacerbate existing geographical health inequities.