RISK OF BREAST-CANCER IN RELATION TO LIFETIME ALCOHOL-CONSUMPTION

Background: Although an association between alcohol consumption and ri sk of breast cancer has been observed in many studies, questions of ma jor importance remain, including the nature of the dose-response relat ionship and the effects of drinking at various periods in life. Purpos e: Our goal was to address the issues listed above with a large case-c ontrol study. Methods: We conducted a population-based case-control st udy in Maine, Massachusetts (excluding the four counties that include metropolitan Boston), New Hampshire, and Wisconsin. Case patients were eligible if their diagnosis of invasive breast cancer was first repor ted to one of the four statewide cancer registries during the period o f 1988 through 1991. During the accrual period, 11 879 potentially eli gible case patients and 16 217 control subjects were identified. After excluding ineligible women from the study, telephone interviews were obtained from 6888 case patients and 9424 control subjects. Complete d ata for recent alcohol consumption, and thus final eligibility for stu dy participation, were determined for 6662 case patients and 9163 cont rol subjects. The average age at time of interview was 58.7 years. The questions on alcohol use addressed average consumption during five pe riods of the subjects' lives: ages 16-19, 20-29, 30-39, 40-59, and 60- 74 years, Similar responses from 211 control subjects upon reinterview 6-12 months later were taken to be indicative of the reliability of t he questionnaire used in this study. Results: Lifetime average alcohol consumption (measured as the average grams per day consumed from age 16 to the recent past) and recent alcohol consumption (average grams p er day consumed in the previous age interval) were associated with ris k of developing breast cancer. The multivariate relative risk of breas t cancer, in those who drink compared with abstainers, associated with average lifetime consumption of 12-18 g/day of alcohol (about one dri nk) was 1.39 (95% confidence interval [CI] = 1.16-1.67), of 19-32 g/da y (about two drinks) was 1.69 (95% CI = 1.36-2.10), of 33-45 g/day (ab out three drinks) was 2.30 (95% CI 1.51-3.51), and of greater than or equal to 46 g/day (four or more drinks) was 1.75 (95% CI = 1.16-2.64) (P for trend <.0001). The multivariate relative risk per 13 g/day (abo ut one drink) of alcohol consumed before 30 years of age was 1.09 (95% CI = 0.95-1.24), whereas the relative risk associated with recent con sumption of 13 g/day was 1.21 (95% CI = 1.09-1.34). Conclusions: In th ese data, alcohol consumption was clearly related to breast cancer ris k. Risk appeared to increase even at moderate levels of consumption, F or women of all ages combined, consumption before 30 years of age was not an important determinant of risk.