Studies of breast cancer and alcohol consumption.

Alcohol consumption as a potential risk factor for breast cancer was examined in a case-control study of 1,467 female breast cancer patients and 10,178 hospital controls. Lean females (Quetelet index less than 22) had elevated unadjusted odds ratios for breast cancer of 2.1, 1.7, and 1.4, associated with consuming less than 5, 5-15, and greater than 15 g of alcohol per day, respectively. However, this pattern is not consistent with a dose-response, and adjustment for a risk profile of confounding factors, including education and occupation (which are strong correlates of age at first pregnancy and parity), reduced these estimates to 1.4, 1.2, and 0.9; none of which differs significantly from 1.0. Among all subgroups, the odds ratios adjusted for pertinent confounders and interactions fluctuated randomly by about 0.9 and showed no consistent trend with increased alcohol consumption. In a second investigation, proportional breast cancer rates were estimated for female veterans diagnosed in Veterans Administration Hospitals during 1970-1982 using 1973-1977 rates for the general population as the standard of comparison. In the VA cohort of females, which had an approximate twofold higher prevalence of alcohol abuse and chronic cigarette smoking, the proportional rates of known alcohol and tobacco-related malignancies were significantly elevated but the rates of breast cancer were not. The standardized proportional morbidity rates of breast cancer for white, black, and all VA females were 0.92, 0.85, and 0.91, respectively. Although these results do not rule out weak associations between breast cancer and alcohol in certain subgroups, neither do they provide any compelling evidence that alcohol has a role in the genesis of this malignancy.