ALCOHOL AND BREAST-CANCER IN WOMEN - A POOLED ANALYSIS OF COHORT STUDIES

Objective.-To assess the risk of invasive breast cancer associated wit h total and beverage-specific alcohol consumption and to evaluate whet her dietary and nondietary factors modify the association. Data Source s.-We included in these analyses 6 prospective studies that had at lea st 200 incident breast cancer cases, assessed long-term intake of food and nutrients, and used a validated diet assessment instrument. The s tudies were conducted in Canada, the Netherlands, Sweden, and the Unit ed States. Alcohol intake was estimated by food frequency questionnair es in each study. The studies included a total of 322 647 women evalua ted for up to 11 years, including 4335 participants with a diagnosis o f incident invasive breast cancer. Data Extraction.-Pooled analysis of primary data using analyses consistent with each study's original des ign and the random-effects model for the overall pooled analyses. Data Synthesis.-For alcohol intakes less than 60 g/d (reported by >99% of participants), risk increased linearly with increasing intake; the poo led multivariate relative risk for an increment of 10 g/d of alcohol ( about 0.75-1 drink) was 1.09 (95% confidence interval [CI], 1.04-1.13; P for heterogeneity among studies, .71). The multivariate-adjusted re lative risk for total alcohol intakes of 30 to less than 60 g/d (about 2-5 drinks) vs nondrinkers was 1.41 (95% CI, 1.18-1.69), Limited data suggested that alcohol intakes of at least 60 g/d were not associated with further increased risk. The specific type of alcoholic beverage did not strongly influence risk estimates. The association between alc ohol intake and breast cancer was not modified by other factors. Concl usions.-Alcohol consumption is associated with a linear increase in br east cancer incidence in women over the range of consumption reported by most women. Among women who consume alcohol regularly, reducing alc ohol consumption is a potential means to reduce breast cancer risk.