Abstract A60: Differences in survival for older compared to younger female breast cancer patients in the California cancer registry by race/ethnicity, insurance, socioeconomic status, and tumor subtype
Authors: Miguel Yazmin San , Tao Li , Gomez Scarlett , Komenaka Ian , Schwab Richard , Thompson Caroline , Nodora Jesse , Murphy James , Martinez Maria Elena 
Published: February 2019

Background: Younger age at diagnosis of breast cancer has been associated with lower survival when compared to older patients. Survival differences by race/ethnicity, socioeconomic status (SES), health insurance, and tumor subtype have been documented in the literature. However, how these sociodemographic and clinical factors affect cancer mortality in younger versus older women is unknown.

Methods: The study used data from the population-based California Cancer Registry, which included invasive female breast cancer cases with Stage I-III disease, 18 years of age and older when diagnosed between 2005 and 2014. Follow-up was completed through December 31, 2014. Tumor subtypes were classified into four categories: hormone receptor (HR) positive (ER and/or PR positive) and HER2 negative (HR+/HER2-), HR+/HER2+, HR-/HER2+, and triple-negative (HR-/HER2-). Multivariate Cox proportional hazards modeling was used to generate mortality rate ratios (MRR) and 95% confidence intervals (CI) for older (50+ years) versus younger (&lt;50 years) patients. We conducted stratified analysis by race/ethnicity, neighborhood socioeconomic status (nSES), insurance status, and tumor subtype.

Results: Among 156,828 breast cancer cases, 2,391 breast cancer deaths occurred in patients &lt;50 years of age and 13,833 in those 50+ years. Risk of dying from breast cancer was higher in older than younger patients (MRR=1.13; 95% CI, 1.07-1.19), after adjusting for multiple patient and tumor characteristics. MRRs comparing older to younger patients varied by racial/ethnic group, with highest risk observed for non-Hispanic white (NHW) women (MRR=1.20; 95% CI, 1.11-1.30) and null findings shown for Asian/Pacific Islander patients (MRR=1.00; 95% CI, 0.85-1.18). Small differences in survival between older and younger patients across levels of nSES were observed, with no clear trend across quintiles. MRRs (95% CI) comparing older vs. younger patients ranged from 1.06 (0.95-1.18) for women with Medicaid/public/military insurance to 1.20 (1.10-1.29) for privately insured patients. Higher MRRs comparing older to younger patients were observed for HR+/HER2- (MRR=1.25; 95% CI, 1.14-1.37) and HR+/HER2+ (MRR=1.42; 95% CI, 1.18-1.71) tumors but not for HR-/HER2+ (MRR=0.91; 95% CI, 0.77-1.08) or triple-negative tumors (MRR=1.03; 95% CI, 0.94-1.13).

Conclusion: Results from our population-based study show that breast cancer patients 50 years and older have lower survival than those under the age of 50. Variations by race/ethnicity and tumor subtype were observed. The results provide evidence of the racial/ethnic and tumor subtype differences in survival for younger versus older breast cancer patients. Understanding reasons for these differences is an important direction for future research.

Citation Format: Yazmin San Miguel, Li Tao, Scarlett Gomez, Ian Komenaka, Richard Schwab, Caroline Thompson, Jesse Nodora, James Murphy, Maria Elena Martinez. Differences in survival for older compared to younger female breast cancer patients in the California cancer registry by race/ethnicity, insurance, socioeconomic status, and tumor subtype [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr A60.