Alcohol consumption increases breast cancer incidence risk in women with varying intake levels.

BACKGROUND: While alcohol consumption appears to influence the incidence of breast cancer (BC), its association with prognosis after a BC diagnosis remains less established. This meta-analysis aimed to explore the association between alcohol consumption on both BC incidence and outcomes. METHODS: A systematic literature search was conducted up to May 1st, 2025 (CRD42025593784). Retrospective and prospective studies reporting BC incidence, recurrences, and survival outcomes in women with history of alcohol consumption were included. Analyses according to alcohol intake levels (light, intermediate, heavy consumption) were performed. Main outcomes were BC incidence, BC recurrences, BC-specific survival (BCSS), and overall survival (OS). Pooled relative risk (RR) and hazard ratio (HR) with 95% confidence interval (CI) were calculated. RESULTS: Out of 5208 screened records, 37 studies including 2,565,920 women were included. Among 17 studies reporting on BC incidence, any alcohol consumption was associated with an increased BC incidence (RR 1.17, 95%CI 1.09-1.26; p < 0.001). BC incidence increased proportionally with higher levels of alcohol consumption: light RR 1.13 (95%CI 1.05-1.23; p = 0.002), intermediate RR 1.28 (95%CI 1.18-1.39; p < 0.001)​, and heavy consumption RR 1.52 (95%CI 1.38-1.67; p < 0.001). Among 20 studies assessing BC outcomes, no associations were found between alcohol consumption and BC recurrences (RR 1.02, 95%CI 0.93-1.11) nor BCSS (HR 0.93, 95%CI 0.87-1.00), while light and intermediate alcohol consumption were associated with slightly improved OS: HR 0.85 (95%CI 0.78-0.92; p < 0.001) and HR 0.84 (95%CI 0.75-0.94; p = 0.002), respectively. CONCLUSIONS: Among over 2.5 million women, alcohol consumption was associated with a dose-dependent increased risk of BC, while alcohol consumption did not appear to worsen prognosis in patients with prior BC diagnosis.