Heterogeneity of breast cancer subtypes and survival among Hispanic women with invasive breast cancer in California

There are limited data regarding breast cancer subtypes among Hispanic women. The current study assessed the distribution and prognosis of molecular subtypes defined by joint expression of the hormone receptors (HR; estrogen and progesterone) and human epidermal growth factor receptor 2 (HER2). Using California Cancer Registry data, we identified Hispanic women diagnosed with invasive breast cancer from 2005 to 2010. Breast cancer subtypes were defined as HR+/HER2-, HR+/HER2+, HR-/HER2+, and HR-/HER2- (triple negative). We estimated breast cancer subtype frequencies and used polytomous logistic regression, Kaplan-Meier survival plots and Cox regression to examine differences in relation to demographic and clinical characteristics. Among 16,380 Hispanic women with breast cancer, HR+/HER- subtype was the most common (63 %), followed by triple negative (16 %), HR+/HER2+ (14 %), and HR-/HER2+ (8 %). Women in lower SES neighborhoods had greater risk of triple negative and HR-/HER2+ subtypes relative to HR+/HER2- (p < 0.05). Hispanic women with triple negative and HR-/HER2+ tumors experienced poorer survival than those with HR+/HER- tumors. Breast cancer-specific mortality increased with decreasing SES, relative to the highest SES quintile, from HR = 1.38 for quintile 4 to HR = 1.76 for quintile 1 (lowest SES level). Our findings indicate that Hispanic women residing in low SES neighborhoods had significantly increased risk of developing and dying from HR- than HR+ breast cancers. Similar patterns of subtype frequency and prognosis among California Hispanic women and studies of other racial/ethnic groups underscore the need to better understand the impact of SES on risk factor exposures that increase the risk of breast cancer subtypes with poor prognosis.