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.