Prognosis of Patients with Breast Cancer Following Delayed Diagnosis During the COVID-19 Pandemic: A Real-World Cohort Study

Background: The coronavirus disease 2019 (COVID-19) pandemic has globally impacted healthcare systems, delaying cancer screening, diagnosis, and treatment. South Korea experienced a 3-month lockdown during the peak of the pandemic, leading to postponements in breast cancer diagnosis and treatment. Although the pandemic's severity has decreased, addressing the treatment gap remains a concern. Methods: This retrospective cohort study included patients diagnosed with breast cancer at five academic hospitals in South Korea during the pre-COVID (May–July 2019) and COVID (May–July 2020) periods. The primary endpoint was recurrence-free survival (RFS), and secondary endpoints included overall survival (OS), stage distribution, and age subgroup analyses. Results: Among 716 patients (374 pre-COVID, 342 COVID), the 3-year RFS was significantly lower in the COVID group (88.3 vs. 89.7%, p = 0.030), while the 3-year OS was similar between groups (96.2 vs. 95.5%, p = 0.439). Age subgroup analysis revealed a significant RFS difference in patients under 65 years of age (p = 0.005) but not in those aged 65 years and older (p = 0.682). Stage distribution did not differ significantly between groups (p = 0.531). Conclusions: The COVID-19 pandemic adversely affected 3-year RFS, especially among younger patients, despite no significant increase in advanced-stage distribution. Timely cancer screening remains crucial for young patients with fewer infectious disease complications.