Differences in breast tumor subtype according to family history of breast cancer among Hispanic Women

B45

Pathologic differences have been reported among breast tumors when comparing ethnic populations. Limited research has been done to evaluate the relationship between breast cancer risk factors and the pathologic features of breast cancer among different ethnic populations. Given that family history of breast cancer represents one of the biggest risk factors and genetic variation is likely to contribute to ethnic-related etiologic differences in breast cancer, the purpose of this study was to determine whether breast tumor characteristics differ among Hispanic and non-Hispanic white (NHW) women according to family history among women in the 4-Corners’ Breast Cancer Study. This study is a population-based, case-control study of breast cancer designed to investigate various factors that may contribute to disparities in breast cancer outcomes among Hispanic and NHW women. Women ages 25-79 at diagnosis of breast cancer (1999-2002) were recruited from the Southwest United States (Arizona, Colorado, New Mexico, and Utah). Participants completed an interview, which included questions regarding reproductive history, family history, and other breast cancer risk factors. Data describing tumor characteristics, such as stage, grade, histology, estrogen and progesterone receptor status, were obtained through the Surveillance, Epidemiology, and End Results (SEER) cancer registry or the state tumor registry database. Using univariate and multivariate methods, we initially evaluated the relationship between family history of breast cancer and pathologic characteristics of the invasive breast tumors among 525 Hispanic and 1012 NHW women in the Study. Among NHW women with breast cancer, there were no significant differences in any of the prognostic factors when comparing women with to those without a family history. Among Hispanic women, cases with a family history had a significantly lower proportion of ER positive tumors compared to cases without a family history (44% versus 58%, P=0.03). This relationship remained significant when adjusting for other prognostic factors. We also evaluated the relationship between family history and risk of ER-defined breast cancer (1537 cases and 2452 controls). Among NHW women, having a family history of breast cancer was associated with a borderline significant 1.43-fold increased risk (95% CI: 0.95-2.16) of ER negative breast cancer and a significant 2-fold increased risk (95% CI: 1.59-2.50) of having an ER positive breast cancer when compared to women without breast cancer. Among Hispanic women, having a family history was associated with a 2.5-fold increased risk of ER negative breast cancers (95% CI: 1.48-4.12), but no association was observed for ER positive breast cancers (OR=1.06, 95% CI: 0.73-1.56). The odds ratios were significantly different between Hispanics and NHW for the relationship between family history and ER positive tumors (P, interaction = 0.007), but not for ER negative tumors (P, interaction = 0.20). These results may reflect ethnic-specific predisposing genetic factors that promote the development of specific breast tumor subtypes and emphasize the importance of evaluating the relationship between breast cancer risk factors and breast tumor subtypes among different ethnic populations.