The joint contribution of tumor phenotype and education to breast cancer survival disparity between Hispanic and non-Hispanic white women

Some studies suggest that Hispanic women are more likely to have ER- and triple-negative (ER-/PR-/HER2-) tumors and subsequently poorer prognosis than non-Hispanic white (NHW) women. In addition, only a handful of studies have examined period-specific effects of tumor phenotype and ethnicity on breast cancer survival, leaving the time-varying effects of hormonal status and ethnicity on breast cancer survival poorly defined. This study describes short and long-term breast cancer survival by ethnicity at 0-5 years and 5+ years post-diagnosis using data from the New Mexico Health, Eating, Activity, and Lifestyle cohort of Hispanic and NHW women ages 29-88 years newly diagnosed with stages I-IIIA breast cancer. The survival rate for Hispanics at 0-5 years was 82.2 % versus 94.3 % for NHW. Hispanics were more likely to have larger tumors, more advanced stage, and ER- phenotypes compared to NHW women. There was a significantly higher risk of breast cancer mortality in Hispanics over 5 years of follow-up compared to NHW (HR = 2.78, 95 % CI 1.39-5.56), adjusting for age, tumor phenotype, stage, and tumor size. This ethnic difference in survival, however, was attenuated and no longer statistically significant when additional adjustment was made for education, although a > 1.5-fold increase in mortality was observed. In contrast, there was no difference between ethnic groups for survival after 5 years (HR = 1.08, 95 % CI 0.36-3.24). Our results indicate that the difference in survival between Hispanic and NHW women with breast cancer occurs in the first few years following diagnosis and is jointly associated with tumor phenotype and socio-demographic factors related to education.