Abstract A73: Breast cancer subtype distribution and survival among Hispanic women in California
Authors: Banegas Matthew P. , Tao Li , Altekruse Sean , Anderson William F. , John Esther M. , Clarke Christina A. , Gomez Scarlett L. 
Published: May 2015

Background: Evidence on the burden of breast cancer subtypes among Hispanic women is limited, as prior research suggests that Hispanics may be prone to develop those subtypes that are associated with poor prognosis. Additionally, few studies have characterized the population-based distribution of breast cancer subtypes among Hispanic women, by the joint expression of hormone receptors (HR: estrogen receptor (ER) and/or progesterone receptor (PR)), and human epidermal growth factor receptor 2 (HER2).

Purpose: Our objective was to assess the distribution and survival of breast cancer subtypes among Hispanic women diagnosed with primary, invasive breast cancer between 2005 and 2010 in California.

Methods: Based on information from the California Cancer Registry, breast cancer subtypes were defined as: HR positive/HER2 negative (HR+/HER2-); HR+/HER2+; HR-/HER2+; and triple negative (HR-/HER2-). We calculated frequency distributions of breast cancer subtypes and used polytomous multivariate logistic regression to evaluate their associations with clinical and demographic factors, including socioeconomic status (SES) and Hispanic enclave (based on quintile distribution across the state of California), and nativity. Kaplan-Meier and Cox proportional hazards regression methods were used to assess breast cancer-specific survival and mortality.

Results: Among 16,380 Hispanic breast cancer patients, HR+/HER- was the predominant subtype (62.6%), followed by triple negative (15.6%), HR+/HER2+ (13.8%) and HR-/HER2+ (8.1%). Women living in lower SES neighborhoods had a greater risk of triple negative (p&lt;0.01) and HR-/HER2+ (p&lt;0.01) subtypes. Hispanic women diagnosed with triple negative and HR-/HER2+ tumors were substantially more likely to die from the disease (HR=5.00, 95% CI:4.19-5.96 and HR=2.74, 95% CI:2.20-3.41, respectively) than patients with the HR+/HER- subtype. Breast cancer-specific mortality increased with decreasing SES, from HR=1.37 (95% CI:0.97-1.93) for quintile 4 to HR=1.77 (95% CI:1.25-2.51) for quintile 1 (lowest neighborhood SES level).

Conclusion: In the most comprehensive analysis of breast cancer subtypes among Hispanic women in the United States to date, our findings indicate that low SES was significantly associated with increased risk of developing and dying from breast cancer subtypes with poor prognosis. Foreign-born women were at greater risk than US-born of HR-/HER2+ tumors, although nativity was not associated with other subtypes. Hispanic women diagnosed with HR- breast cancer subtypes were at significantly increased risk of death; especially, those with triple negative breast cancer. While these results indicate that the distribution and burden of breast cancer subtypes among California Hispanic women are similar to other racial/ethnic populations, it is imperative to better understand the impact of SES on risk factor exposures that increase the risk of developing specific breast cancer subtypes.

Citation Format: Matthew P. Banegas, Li Tao, Sean Altekruse, William F. Anderson, Esther M. John, Christina A. Clarke, Scarlett L. Gomez. Breast cancer subtype distribution and survival among Hispanic women in California. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr A73. doi:10.1158/1538-7755.DISP13-A73