Cigarette smoking and breast cancer

Abstract

To investigate the relationship of smoking to breast cancer risk, the authors conducted a case-control study involving 1,547 patients and 1,930 controls identified between 1973 and 1980 through a nationwide screening program. There was no evidence that smoking affected risk (relative risk (RR) = 1.2), nor were there any apparent relationships with more detailed exposure measures. No substantial variations in risk were noted by menopausal status; in particular, there was no support for the notion that smoking is associated with a reduced risk among naturally menopausal women (RR = 1.1). In addition, the data provided no general evidence that smokers experience an earlier menopause than nonsmokers, even when heavy smoking was considered. Evaluation of a number of sources of confounding and effect modification failed to alter the conclusion that smoking status does not appear to alter breast cancer risk among this population.

PIP: The association between cigarette smoking and breast cancer risk was investigated in a case-control study involving 1547 patients and 1930 controls identified in 1973-80 through a multicenter breast cancer screening program. A total of 47.8% of the cases and 43.4% of the controls reported ever having smoked 100 or more cigarettes--resulting in a relative risk of 1.2 (95% confidence interval, 1.0-1.4). There was little variation in risk according to whether women were current or noncurrent smokers or by number of years smoked, number of cigarettes consumed/day, and age at which smoking began. In addition, no substantial variations in risk were noted by menopausal status, and there was no support for the notion that smoking is associated with a reduced risk among naturally menopausal women (relative risk, 1.1). The data further provided no evidence that smokers experience an earlier menopause than nonsmokers. The conclusion that smoking status does not appear to affect breast cancer risk remained unaltered even after evaluation of numerous other sources of confounding and effect modification, including family history of breast cancer, weight, age at 1st live birth, and oral contraceptive use.