Risk factors associated with the triple-negative breast cancer subtype within four race/ethnicities.

PURPOSE: The ER-/PR-/HER2- or triple-negative (TNBC) subtype is more prevalent among women who are young, black, Hispanic, and of lower SES. The purpose of this study is to determine if young age and low SES are associated with TNBC within four mutually exclusive race/ethnicities.

METHODS: The study identified 19,283 cases of TNBC and 89,089 of ER+/PR+/HER2- from the California Cancer Registry. Logistic regression analyses were conducted separately for whites, blacks, Hispanics, and Asian/Pacific Islanders (API) to compute the adjusted odds ratios (OR) for age and SES for the TNBC versus the ER+/PR+/HER2- subtype.

RESULTS: White (OR=1.37;1.23-1.53) and Hispanic and women (OR=1.35;1.17-1.56) 30-39 had increased odds of the TNBC when compared with women 50-59 of the same race/ethnicity. Black women under 40 had the same odds, and black women 40-49 had lower odds of the TNBC as black women 50-59. White, black, and Hispanic women 70 and older had decreased or the same odds of the TNBC as 50 to 59-year-old women. API women had a similar risk of TNBC at all ages. Lower SES was associated with increased risk of TNBC only for white and Hispanic women. The odds of TNBC were no worse for API women with lower SES than API women with higher SES. SES was not statistically significant for black women.

CONCLUSIONS: When assessing the odds of TNBC within a single race/ethnicity, young age and low SES are risk factors only for white and Hispanic women, but not for black and API women.