Association of family history and other risk factors with breast cancer risk among Japanese premenopausal and postmenopausal women

Objectives: To determine the impact of family history (FH) on anthropometric and reproductive risk factors for breast cancer, a case-referent study was conducted using data from the Hospital-based Epidemiologic Research Program at Aichi Cancer Center (HERPACC), Japan. Methods: In total, 1584 breast cancer cases were included and 15,331 women, confirmed as free of cancer, were recruited as the referents. Odds ratios and 95% confidence intervals were determined by logistic regression analysis. Separate analyses were performed for premenopausal and postmenopausal women. Results: Height, weight, and current body mass index (BMI) were positively associated with postmenopausal breast cancer regardless of FH, while these anthropometric factors did not alter risk in premenopausal women. The impacts of height and weight on postmenopausal breast cancer were more pronounced among FH women. There was little association with reproductive risk factors for premenopausal or postmenopausal breast cancer in FH cases, in clear contrast to the non-FH cases. Conclusions: These findings suggest some differences in risk impact of common etiologic factors between familial breast cancer and sporadic cases that may give pointers to further analysis of host-specific factors. They imply that avoidance of obesity after menopause may reduce the risk of breast cancer, regardless of FH.