CIGARETTE SMOKING AND BREAST CANCER

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.