Population-based outcomes of chemoradiation therapy for muscle-invasive bladder cancer in older adults

Introduction We aimed to evaluate population-based outcomes of chemoradiation therapy (CRT) for muscle-invasive bladder cancer given a lack of population-based data, particularly in older adults. Materials and methods We conducted observational analyses using SEER-Medicare based on the CRT protocol in the control arm of SWOG/NRG 1806. We included adults aged 66–89 years with T2-T4a N0 M0 urothelial bladder cancer treated with radiation and concurrent chemotherapy (cisplatin, gemcitabine, or 5-FU + mitomycin C) within 90 days of transurethral resection of bladder tumor (TURBT) from 2000 to 2017. We examined progression-free (PFS), cancer-specific (CSS), and overall survival (OS) using claims-based proxies and the Kaplan-Meier method. Associations of baseline characteristics with outcomes were evaluated using Cox regression. Results A total of 283 patients were included. Median age was 78 years (IQR 73–82), and tumor stage was T2 in 247 (87%) patients. Median follow-up was 26.0 months. At five years, PFS was 47%, CSS was 53%, and OS was 35%. On multivariable analysis, female sex (HR 1.74) was associated with increased risk of cancer-specific mortality (CSM), while higher education level (HR 0.37 for <14% without high school education versus >29%) was associated with reduced CSM. Discussion Notwithstanding the limitations of SEER-Medicare, in observational analyses designed to evaluate outcomes of a hypothetical single-arm trial, CRT was associated with lower CSS and OS than reported in prior clinical trials. Additional studies are required to determine if this is related to the efficacy or completeness of CRT in population-based practices or differences between trial and non-trial populations.