Family history and breast cancer subtype among women of Mexican descent.

Abstract

41 Background: A family history of breast cancer in a first-degree relative is associated with a 2-fold increase in breast cancer risk; however, breast cancer is a heterogeneous disease and there may be differences in risk profiles driven by tumor subtype or by racial/ethnic group. Methods: We assessed prevalence of familial breast cancer and its association with tumor subtype among 914 women with breast cancer of Mexican descent enrolled in the Ella Study, a case-only, binational (U.S.-Mexico) breast cancer study. Logistic regression was conducted to compare odds of triple negative breast cancers to non triple-negative breast cancers according to family history. Results: The prevalence of family history of breast cancer in a first- or second-degree relative was 24.1%, with 13.1% having an affected first-degree relative. Among participants who were diagnosed at age < 50, prevalence of family history of breast cancer in a first- or second-degree relative was 27.4%. After adjustment for age and country of residence, women with a first-degree relative with breast cancer were significantly more likely to be diagnosed with triple-negative breast cancers compared to non triple-negative breast cancers (OR = 1.98; 95% CI, 1.26-3.11). Similar results were seen for odds of triple-negative breast cancers compared to non-triple negative breast cancers for women with affected first- or second-degree relatives (OR=2.04; 95% CI, 1.40–2.98). The odds of triple-negative breast cancer compared to non-triple negative breast cancer was 1.93 (95% CI, 1.26–2.97) for women with first-degree relatives affected with breast or ovarian cancer. Conclusions: Findings suggest that familial cancers are most likely to be associated with triple negative subtype, supporting etiologic heterogeneity by tumor subtype in this population of Hispanic women. This association may be related to the prevalence of BRCA1 founder mutations in this population, which are strongly associated with triple-negative breast cancers. Identification of such differences in risk factors can help personalize screening and prevention approaches.