Associations between frailty and cancer-specific mortality among older women with breast cancer

Purpose Frailty is assessed when making treatment decisions among older women with breast cancer (BC), which in turn impacts survival. We evaluated associations between pre-diagnosis frailty and risks of BC-specific and all-cause mortality in older women. Methods We conducted a retrospective cohort study of Medicare beneficiaries ages ≥ 65 years with stage I-III BC using the Surveillance, Epidemiology and End Results-Medicare Health Outcome Survey Data Resource. Frailty was measured using the deficit-accumulation frailty index, categorized as robust, pre-frail, or frail, at baseline and during follow-up. Fine and Gray competing risk and Cox proportional hazards models were used to estimate subdistribution hazard ratios (SHR) and hazard ratios (HR) with 95% confidence intervals (CI) for BC-specific and all-cause mortality, respectively. Results Among 2411 women with a median age of 75 years at BC diagnosis, 49.5% were categorized as robust, 29.4% were pre-frail and 21.1% were frail. Fewer frail women compared to robust women received breast-conserving surgery (52.8% vs. 61.5%, frail vs. robust, respectively) and radiation (43.5% vs. 51.8%). In multivariable analyses, degree of frailty was not associated with BC-specific mortality (frail vs robust SHR 1.47, 95% CI 0.97-2.24). However, frail women with BC had higher risks of all-cause mortality compared to robust women with BC (HR 2.32, 95% CI 1.84-2.92). Conclusion Among a cohort of older women with BC, higher degrees of frailty were associated with higher risk of all-cause mortality, but not BC-specific mortality. Future study should examine if preventing progression of frailty may improve all-cause mortality.