Optimal timing of chemoradiotherapy after surgical resection of glioblastoma: Stratification by validated prognostic classification

Background Previous studies examining the time to initiate chemoradiation (CRT) after surgical resection of glioblastoma have been conflicting. To better define the effect that the timing of adjuvant treatment may have on outcomes, the authors examined patients within the National Cancer Database (NCDB) stratified by a validated prognostic classification system. Methods Patients with glioblastoma in the NCDB who underwent surgery and CRT from 2004 through 2013 were analyzed. Radiation Therapy Oncology Group recursive partitioning analysis (RPA) class (III, IV, V) was extrapolated for the cohort. Time intervals were grouped weekly, with weeks 4 to 5 serving as the reference category for analyses. Kaplan‐Meier analysis, log‐rank testing, and multivariate (MVA) Cox proportional hazards regression were performed. Results In total, 30,414 patients were included. RPA classes III, IV, and V contained 5250, 20,855, and 4309 patients, respectively. On MVA, no time point after week 5 was associated with a change in overall survival for the entire cohort or for any RPA class subgroup. The periods of weeks 0 to 1 (hazard ratio [HR], 1.18; 95% CI, 1.02‐1.36), >1 to 2 (HR, 1.23; 95% CI, 1.16‐1.31), and >2 to 3 (HR, 1.11; 95% CI, 1.07‐1.15) demonstrated slightly worse overall survival (all P