Abstract PD2-7: Vigorous exercise across the lifespan and reduced risk of estrogen receptor negative breast cancer in African American women

Abstract

Abstract Background. Recreational exercise has been associated with a reduced risk of breast cancer, but evidence regarding breast cancer among African American women and about breast cancer subtypes is sparse. Methods. We assessed lifetime vigorous exercise (average of high school, age 21, age 30, and baseline) in the Black Women's Health Study in relation to the incidence of invasive breast cancer overall (n = 1,377), estrogen receptor-positive (ER+) breast cancer (n = 556), estrogen receptor-negative (ER-) breast cancer (n = 327), and triple negative breast cancer (TN) (n = 103); analyses were based on 275,188 person years of follow-up of 44,704 African American women who were aged 30 or more at entry to the study. Cox proportional hazards models estimated incidence rate ratios (IRR) and 95% confidence intervals (CI), controlling for breast cancer risk factors. Results. For ER- breast cancer, the IRRs for 1-2.2 hours/week, 2.3-2.9 hours/week, and 3+ hours/week relative to <1 hour/week were 0.76 (95% CI 0.52-1.11), 0.78 (95% CI 0.52-1.17) and 0.53 (95% CI 0.31-0.90), respectively; the p value for trend was 0.058. The inverse association was apparent only among postmenopausal women. There was also an inverse association, although nonsignificant, of exercise with the incidence of TN breast cancer. Vigorous exercise was not associated with a reduction in ER+ breast cancer risk. Conclusion. These results indicate that physical activity may protect against the development of ER- breast cancer in African American women. The association, if confirmed, is of great public health importance given the high mortality associated with this subtype and its higher incidence in African American women. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD2-7.