Prenatal DES exposure in relation to breast size
Prenatal DES exposure has been associated with increased risk of breast cancer, but the mechanisms are unknown. Larger bra cup size has also been associated with increased breast cancer risk, although not consistently. We investigated the relation of prenatal DES exposure to mammary gland mass, as estimated by bra cup size.
In 2006, 3,222 DES-exposed and 1,463 unexposed women reported their bra cup size, band size (chest circumference), and weight at age 20. Prevalence ratios (PR) were calculated for DES exposure in relation to large bra cup size, with control for year of birth and study cohort. Primary analyses were carried out among women who reported a chest circumference of no more than 32 inches because their cup size would be less influenced by fat mass.
Within this group, DES-exposed women had an estimated 45 % increased prevalence (95 % CI 0.97–2.18) of large cup size (C or greater) relative to unexposed women. The PR was further increased among women in this group who had a body mass index of < 21 at age 20: PR = 1.83 (95 % CI 1.11–3.00). The PR for high-dose DES exposure relative to no exposure was 1.67, 95 % CI 1.02–2.73, whereas there was no association of bra cup size with low-dose exposure.
These results provide support for the hypothesis that in utero DES exposure may result in greater mammary gland mass. Taken together with previous research on bra size and breast cancer risk, these findings suggest a mechanism for a possible association of in utero DES exposure with increased risk of breast cancer.
KeywordsBreast Cancer Risk Prevalence Ratio Increase Breast Cancer Risk Breast Size Chest Circumference
This research was support by a contract from the National Cancer Institute, National Institutes of Health, U.S. Department of Health and Human Services. We thank the field center study managers, Diane Anderson, Elizabeth Barnard, Toni Oliver, Elaine Campbell, Polly Goralski, Kathleen Rowlings, Helen Bond, Ann Urbanovitch, and Kathyln Tucke. We also appreciate the support of Cathy Ann Grundmayer, Shelley Niwa, and Bob Saal of Westat, Inc., for study-wide coordination efforts. Finally, we thank the DES-exposed and unexposed daughters for their longstanding participation in this study.