Interactions between alcohol consumption and adjuvant hormone therapy in relation to breast cancer-free survival

Purpose: Alcohol consumption is associated with an increase in breast cancer risk, but findings on the association of alcohol with survival after breast cancer diagnosis have been inconsistent. Further, whether these associations could differ by adjuvant hormone therapy status is unknown. We examined interactions between alcohol consumption and adjuvant hormone therapy in relation to breast cancer-free survival among women with a primary breast cancer diagnosis. Methods: Participants in this study included 1,399 women diagnosed with primary breast cancer between 2007 and 2012 at the Moffitt Cancer Center. Alcohol consumption during the year preceding diagnosis was assessed in a patient survey. Information on tumor characteristics, breast cancer treatment and outcomes was available from the Moffitt Cancer Registry. Associations were examined using Cox proportional hazards models in stratified analyses by adjuvant hormone therapy status, after adjustment for potential con-founders. Results: Overall, alcohol consumption was associated with significantly improved breast cancer-free survival (any vs. none: hazard ratio [HR], 0.77; 95% confidence interval [CI], 0.65–0.92). Among women without adjuvant hormone therapy, alcohol consumption was associated with better survival in heavy drinkers (HR, 0.63; 95% CI, 0.43–0.93). Among women with adjuvant hormone therapy, survival was better in women consuming alcohol as compared to nondrinkers (moderate: HR, 0.69, 95% CI, 0.51–0.93; heavy: HR, 0.74, 95% CI, 0.57–0.96; any: HR, 0.71, 95% CI, 0.57–0.87). There was no significant interaction between alcohol and adjuvant hormone therapy (p-interaction=0.54 for alcohol modeled as none or any and p= 0.34 for alcohol modeled as none, moderate, and heavy). Conclusion: Associations of alcohol consumption with breast cancer-free survival are similar in women with and without adjuvant hormone therapy. Future studies are warranted to elucidate potential mechanisms underlying the observed inverse associations.