Alcohol use and subsequent primary cancer in breast cancer survivors: A case-cohort study.

Abstract

e22562 Background: With continued advances in treatment, there are an increasing number of breast cancer survivors at risk of developing a second primary cancer. Not much is known about modifiable behaviors such as alcohol use on the risk of second primary cancers in breast cancer survivors. Here we evaluated the associations between alcohol use and risk of the four most common second primary cancers in a population-based case-cohort study. Methods: We identified a total of 2630 breast cancer survivors from the Seattle-Puget Sound region including 1930 cases who developed a second primary cancer (602 breast, 621 lung, 300 colorectal, and 307 endometrial) and 800 non-cases who did not develop a second primary cancer. Alcohol exposure was assessed by interview at first breast cancer diagnosis as never, former or current. Alcohol dose was further classified as heavy use (4 or more drinks a week) or moderate use (< 4 drinks a week). Associations between alcohol use and second primary cancer risk were assessed using multivariable Cox proportional hazards models adjusting for age, year of diagnosis, histology, estrogen receptor status, stage, and confounders that changed estimates by 10%. Results: Ongoing alcohol use at initial breast cancer diagnosis was associated with a more than 2.5-fold increased risk of developing lung cancer [hazard ratio (HR): 2.57, 95% confidence interval (CI): 1.52-4.34]. Former alcohol use also appeared to increase lung cancer risk but did not reach statistical significance (HR: 1.95, 95% CI: 0.97-3.92). The association between ongoing alcohol use and developing lung cancer was not observed to be dose dependent. Ongoing alcohol was associated with a reduced risk of developing endometrial cancer, but the risk estimate was within the limits of chance (HR: 0.69, 95% CI: 0.44-1.06). Former alcohol use was not associated with developing endometrial cancer (HR: 0.96, 95% CI: 0.32-2.90). The protective association between ongoing alcohol use and developing endometrial cancer appeared to be dose dependent (HR for moderate use: 0.92, 95% CI: 0.55-1.55 vs. HR for heavy use: 0.39, 95% CI: CI 0.22- 0.70). Ongoing or former alcohol use at initial breast cancer diagnosis was not associated with risk of developing either a second breast cancer or a subsequent colorectal cancer. Conclusions: These findings suggest that alcohol remains an important modifiable risk factor for specific secondary cancers in breast cancer survivors and have important implications on risk assessment for tailored surveillance and preventative strategies for breast cancer survivors.