Background: Alcohol consumption has been comprehensively investigated as an etiologic risk factor for breast cancer but has received little attention in terms of its effect on prognosis after breast cancer, particularly for young women.

Methods: 1,286 women diagnosed with invasive breast cancer at age < or =45 years from two population-based case-control studies in the Seattle-Puget Sound region were followed from their diagnosis of breast cancer (between January 1983 and December 1992) for survival through June 2002, during which time 364 women had died. Cox proportional hazards modeling was used to assess the effect of prediagnostic alcohol consumption on the risk of dying.

Results: After adjusting for age and diagnosis year, compared with nondrinkers, women who consumed alcohol in the 5 years before diagnosis had a decreased risk of death [>0 to <3 drinks per week: hazard ratio, 0.7; 95% confidence interval (95% CI), 0.6-0.95; 3 to <7 drinks per week: risk ratio, 0.6; 95% CI, 0.4-0.8;7 drinks per week: risk ratio, 0.7; 95% CI, 0.5-0.9]. This association was unchanged on additional adjustment for potential confounders including most notably treatment, stage at diagnosis, and mammogram history.

Conclusion: These results suggest that women who consume alcohol before a diagnosis of breast cancer have improved survival, which does not appear to be attributable to differences in stage, screening, or treatment.