Abstract 5739: Lifetime recreational physical activity, hormone therapy use and breast cancer risk in postmenopausal women

Abstract

Abstract Studies consistently demonstrate that physical activity is inversely associated with postmenopausal breast cancer. Whether the strength of this association varies with exposure to menopausal hormone therapy (HT) is clearly important given the marked decline in HT use since 2002. The Women's Contraceptive and Reproductive Experiences Study, a multi-center population-based case-control study of invasive breast cancer recruited white women and black women ages 35-64 years, and collected histories of lifetime exercise activity and HT use. Unconditional logistic regression models assessed possible associations between lifetime exercise activity measures (hr/wk/yr and metabolic equivalents of energy expenditure [MET]-hrs/wk/yr) and breast cancer among postmenopausal women (1908 case patients, 2013 control subjects) stratified by duration of HT use (never, ≤5 years of use, or ≥5 years of use), and current HT-use status (current use of estrogen-alone therapy [ET], current use of estrogen plus progestin therapy [EPT], or past HT use). Breast cancer risk decreased as level of physical activity increased among women who had never used HT, among women who used HT for fewer than 5 years, and among current ET users; Ptrend values ranged from 0.004 to 0.019. Despite the lack of association among long-term HT users, current EPT users, and past HT users, no statistical heterogeneity of trends was observed across duration-of-use categories or by current-use status. Although the inverse association between physical activity and breast cancer was limited to women with no HT use, short duration of HT use or current ET use, this study did not demonstrate effect modification by HT use. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5739.