Purpose: To investigate the association between hormone-related risk factors and breast cancer subtype in African American women. We hypothesized that African American women with triple-negative breast cancer (TNBC) would have a lower prevalence of hormone-related risk factors than women with other breast cancer subtypes (1) hormone receptor [HR +/-] and human epidermal growth factor receptor 2 [HER2-] or (2) HR +/- and HER2+.

Methods: African American women ages 25-75 years diagnosed with primary invasive breast cancer in 2009-2013 in Tennessee, South Carolina, and Georgia were eligible for the study. A total of 629 women (premenopausal n=175; postmenopausal n=454) provided information on hormone-related risk factors in a telephone interview and consented to review of tumor tissue; breast cancer subtype was obtained from pathology reports.

Results: Although not significantly different, pre- and postmenopausal women with TNBC were more likely to have early age at menarche than women with other subtypes. Obesity was higher among pre- and postmenopausal women with HR+/- HER2+ disease and intermediate among women with TNBC relative to women with HR+/- HER2- disease. Oral contraceptive use was less likely among women with TNBC, significantly so for postmenopausal women (odds ratio=0.70, 95% confidence interval=0.53-0.91) than women with other subtypes.

Conclusions: Histologic subtyping is currently being performed on collected tissue to confirm the reported breast cancer subtypes in the pathology reports. The large number of African American women participating in our study can further our understanding of hormone-related risk factors and their relationship with breast cancer subtypes in this population.

Citation Format: Jennifer Davis, Cecilia Jimenez, Chrystina Clinton, Mary Kay Fadden, Loren Lipworth, Maureen Sanderson. Hormone-related risk factors and breast cancer subtype in African American women [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr C064.