Abstract A77: Walking and vigorous exercise and risk of breast cancer in African American women

Abstract

The relationship between physical activity and breast cancer risk has been extensively studied among women of European descent, with most studies reporting an inverse association. However, data on African American (AA) women and by tumor subtypes are sparse. Thus, we examined associations of vigorous exercise and walking for exercise and breast cancer risk overall and by estrogen receptor (ER) status in the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. We pooled data on AA women from four large studies, the Black Women's Health Study, Carolina Breast Cancer Study, Multiethnic Cohort Study and Women's Circle of Health Study, for 2,482 ER+ cases, 1,374 ER- cases and 16,959 controls. Multivariable logistic regression was used to compute odds ratios (OR) and 95% confidence intervals (CI) for the risk of overall breast cancer, and polytomous logistic regression was used to model the risk of ER+ and ER- cancer. Based on all four studies, for recent vigorous exercise (reported by 29% of controls), the OR was 0.88 (95% CI: 0.81-0.96) for breast cancer overall, 0.88 (95% CI: 0.80-0.98) for ER+ breast cancer and 0.93 (95% CI: 0.82-1.06) for ER- breast cancer. There was a statistically significant trend across hours per week of vigorous activity for breast cancer overall (p for trend=0.006) and for ER+ cancer (p for trend=0.02), but there was not a clear dose response relationship, with the strongest reduced risk in the 1-2 and 3-4 hours/week categories. Data on walking for exercise, as the most frequently reported activity among adults who meet guidelines for regular physical activity (53% in controls), was available from two studies. Any walking for exercise was associated with reduced risk of breast cancer overall (OR=0.88, 95% CI: 0.80-0.97) and ER+ cancer (OR=0.87, 95% CI: 0.77-0.98), but not ER- cancer (OR=0.95, 95 CI: 0.81-1.12). There was a significant trend across hours per week of walking for breast cancer overall (p for trend=0.008) and ER+ breast cancer (p for trend=0.02), with the strongest reduced risk in the 5+ hours/week category. Our results from this large pooling study of AA women provide evidence that vigorous exercise and walking for exercise are associated with reduced risk of breast cancer, specifically ER+ cancer.

Citation Format: zhihong Gong, Chi-Chen Hong, Elisa Bandera, Lucile Adams-Campbell, Song-Yi Park, Gary Zirpoli, Andrew Olshan, Christine Ambrosone, Julie Palmer, Lynn Rosenberg. Walking and vigorous exercise and risk of breast cancer in African American women. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr A77.