Incidence and Survival by Human Epidermal Growth Factor Receptor 2 Status in Young Women With Stage I-III Breast Cancer: SEER, 2010-2016.

BACKGROUND: Young premenopausal women with breast cancer often experience more aggressive disease biology and poorer survival than older women. Diagnostic and therapeutic advances, including human epidermal growth factor receptor 2 (HER2)-directed therapy, may lessen treatment burden and improve survival for these young women, but contemporary incidence and survival data by HER2 status are limited. PATIENTS AND METHODS: We identified women aged 20-49 years (n = 68,530) diagnosed with stage I-III breast cancer during 2010-2016 from the United States Surveillance, Epidemiology, and End Results 18 registries database. Age-adjusted average annual percent changes in incidence (diagnosis 2010-2016) and 5-year Kaplan-Meier survival curves (diagnosis 2010-2015) were estimated by HER2 and hormone receptor (HR) status and stratified independently by cancer stage and race/ethnicity. RESULTS: With increasing age decade, proportions of HER2-/HR+ cancer increased, whereas proportions of HER2+/HR+, HER2+/HR-, and HER2-/HR- decreased. The greatest increases in incidence during 2010-2016 were observed for HER2+ among women aged 20-49 years and HER2-/HR- among women aged 20-29 years. Incidence decreased for HER2-/HR- among women aged 40-49 years. Five-year survival was lowest for HER2-/HR- status compared to other receptor-based subtypes among women aged 20-49 years. HER2+ status was more beneficial for 5-year survival than HR+ status among women aged 20-29 years, with the opposite observed among women aged 30-49 years, particularly those aged 40-49 years. CONCLUSION: HER2+ breast cancer increased among premenopausal women and was also associated with higher early survival within each HR status. HER2-/HR- cancer also increased among women aged 20-29 years and was associated with lower early survival. Our contemporary data provide important insights to help inform preventive and therapeutic strategies for premenopausal women.