Abstract D101: Breast cancer in Black women: Do risk factors differ for those who have a family history of breast cancer?
Authors: Zirpoli Gary R , Bethea Traci N , Bernstein Leslie , Troester Melissa A , Ambrosone Christine B , Palmer Julie R 
Published: September 2020

Background: Women who have at least one first-degree relative diagnosed with breast cancer have an almost two-fold risk of developing breast cancer themselves. Therefore, there is particular interest in identifying modifiable factors that can reduce risk. To date, most studies of breast cancer risk in women with a family history of breast cancer have focused on White women. Methods: We pooled questionnaire data on Black women from three case-control studies (Women’s Contraceptive and Reproductive Experiences, Carolina Breast Cancer Study, and Women’s Circle of Health Study) and nested case-control data from the prospective Black Women’s Health Study for an analytic sample of 5,015 invasive breast cancer cases and 15,354 controls; 15.9% of cases and 9.4% of controls reported a first-degree family history of breast cancer (“family history”). We used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for risk of breast cancer overall, and by estrogen receptor (ER) status, within strata of family history. All models were adjusted for age and study. Additional covariates were body mass index (recent and at age 18), adult height, smoking, alcohol consumption, parity, breastfeeding, age at first birth, age at menarche, interval between menarche and first birth, age at menopause, and history of benign breast disease. Results: ORs were consistent among women with and without a family history for most factors. However, associations of parity and breastfeeding with risk of ER negative breast cancer were stronger among women with a positive family history: the OR for ever parous vs. nulliparous was 1.63 (1.11-2.39) among women with a family history and 1.31 (1.13-1.53) among those without. In both groups, the elevated OR associated with parity was reduced if the women had breastfed at least one child. The ORs for ER negative breast cancer associated with parity without breastfeeding were 1.86 (1.25-2.77) and 1.43 (1.22-1.67), among women with and without a family history of breast cancer, respectively (p-interaction &gt;0.05). Additional control for other reproductive factors did not materially change the estimates. Breastfeeding was not associated with risk of ER positive breast cancer in either group. Conclusion: As has been shown previously, parous women were found to be at increased risk of ER negative breast cancer, with the increase attenuated by breastfeeding. Stratification by family history of breast cancer indicated that the associations may be stronger among women with a first-degree family history, although interactions were not statistically significant. Findings from the present study demonstrate that Black women who already have a higher than average baseline risk of ER negative breast cancer due to their familial history may favorably modify their risk by breastfeeding.

Citation Format: Gary R Zirpoli, Traci N Bethea, Leslie Bernstein, Melissa A Troester, Christine B Ambrosone, Julie R Palmer. Breast cancer in Black women: Do risk factors differ for those who have a family history of breast cancer? [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr D101.