The relation of breast size to breast cancer risk in postmenopausal women (United States)

Objective: Breast size has been hypothesized to predict a woman's risk of b reast cancer although studies in the main have not supported an association . In a large, population-based case-control study we examined whether breas t size might emerge as a significant risk factor among very lean women in w hom breast size might be a truer reflection of the volume of gland mass at risk for malignant change. Methods. The data derive from a population-based case-control study of wome n aged 50 to 79 years conducted in several New England states and Wisconsin . Incident cases of invasive breast cancer (n = 2015) were identified throu gh state tumor registries and controls (n = 2556) were selected at random w ithin age strata from population lists. Telephone interviews were conducted to obtain information on known and suspected risk factors which included b ra dimensions (cup and back size) prior to a first birth, or at the age of 20 for nulliparous women. Results: We observed a significant positive association for cup size which was limited to women who were the most lean as young adults based on chest circumference. Among those reporting a chest size under 34 inches multivari ate-adjusted relative risks were 1.34 (95% CI: 1.04 to 1.74) for cup size B , and 1.76 (95% CI: 1.04 to 3.01) for cup size C and larger, compared to a cup size smaller than B, and the trend for increasing cup size was statisti cally significant (P = 0.005). There was no relation with breast size among women reporting an average or larger back circumference (34 inches or larg er). Conclusion: Breast size before a pregnancy is a positive predictor of postm enopausal breast cancer, but this association is limited to those who were especially lean as young women.