Real-world patterns of treatment and recurrence by frailty status among older women with HR-positive, HER2-negative early breast cancer.

535 Background: Frail health status impacts clinical decision making for older cancer patients and their families, and frailty is independently associated with increased risks of mortality. Our objective was to describe differences in treatment and rates of recurrence by frailty status among older women with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative early breast cancer. Methods: We performed a large, population-based retrospective cohort study of women aged 65 years and older diagnosed with first primary stage I-III HR+/HER2-breast cancer using the Surveillance, Epidemiology, and End Results Medicare-linked database between 2007 and 2015. Using administrative health claims, we ascertained information on breast cancer treatment and utilized validated claims-based algorithms to determine frailty status (robust, pre-frail, and frail) and identify subsequent invasive breast cancer recurrences. Relative hazards of recurrence were determined using Fine and Gray competing risks regression models with estimated subdistribution hazard ratios (SHR) and robust 95% confidence intervals (CI). Results: From an overall cohort of 46,027 women, most women (56%) were classified as robust at breast cancer diagnosis, whereas 37% and 7% were identified as pre-frail and frail, respectively. Compared to robust patients, frail patients were more likely to have stage III disease (10% vs. 7%) and receive mastectomy (27% vs. 18%), and less likely to receive radiation (35% vs. 57%) or chemotherapy (5% vs. 9%). Five-year cumulative incidences of recurrence were 15%, 18% and 22% among robust, pre-frail, and frail women, respectively. In multivariable competing risks models adjusted for age, race, stage, and treatment, frail (SHR 1.28, 95%CI 1.17-1.41) and pre-frail (SHR 1.15, 95%CI 1.09-1.21) women had a significantly increased risk of breast cancer recurrence. Conclusions: Independent of differences in treatment, frailty was associated with increased breast cancer recurrence risk in this population-based cohort of older women. However, the vast majority of older women living with HR+/HER2- early breast cancer were not identified as frail. These study results suggest that age alone is not an adequate indicator of physical resilience and underscores the need to consider additional factors when assessing the benefits and risks of treatments for the prevention of recurrence among HR+/HER2- early breast cancer patients.