e12584 Background: The COVID-19 pandemic disrupted cancer diagnostic pathways and screening programmes. The long-term impact on breast cancer presentation patterns and immunohistochemical (IHC) subtype distribution remains incompletely characterised. This study evaluated temporal trends in breast cancer presentations at a regional Irish cancer centre. Methods: A retrospective longitudinal cohort study was conducted including approximately 80% of breast cancer cases from the South East region of Ireland treated at University Hospital Waterford. Patients diagnosed between January 2015–December 2019 (pre-pandemic) and January 2020–December 2024 (pandemic/post-pandemic) were analysed. Tumours were classified by IHC subtype (ER-positive, HER2-positive, triple-negative) and metastatic status. The primary endpoint was change in subtype distribution over time. Secondary endpoints included total case volume and incidence of de novo metastatic disease. Results: Breast cancer diagnoses declined during peak pandemic periods, followed by recovery with a 10% increase in post-pandemic case volume compared with pre-pandemic levels. Subtype analysis demonstrated a 4% increase in ER-positive disease, a 6% reduction in HER2-positive disease, and a 3% increase in triple-negative breast cancer (TNBC). TNBC showed a sustained upward trend following service recovery. The incidence of de novo metastatic disease doubled compared with pre-pandemic baseline. Conclusions: Post-pandemic recovery has been associated with increased breast cancer presentations and a shift towards more aggressive disease phenotypes, including rising TNBC and metastatic disease rates. These findings highlight the downstream impact of diagnostic delays and disrupted screening pathways and support the need for national-level analyses to guide future healthcare service planning.
Mohammed et al. (Thu,) studied this question.