Validation of a novel molecular RPA classification in glioblastoma (GBM-molRPA) treated with chemoradiation: A multi-institutional collaborative study

Abstract

Background and purposeA novel molecular recursive partitioning analysis classification has recently been reported integrating the MGMT promoter methylation (MGMTmeth) and IDH1 mutation (IDH1mut) status for glioblastoma (GBM-molRPA) patients treated with temozolomide-based chemoradiation. The current study was initiated to validate the model in a multi-institutional study. Materials and methodsFour-hundred seventy-one newly diagnosed GBM patients (validation cohort) were allocated to classes I–III of the previously reported GBM-molRPA model. Of the patients, 15.7%, 56.1%, and 28.2% patients were GBM-molRPA class I, II, and III, respectively. MGMTmeth and IDH1mut were observed in 32.3 and 8.8% of patients, respectively. In the training plus validation cohort of 692 patients, 16.2%, 60.8%, and 23.0% patients were class I, II, and III, respectively. ResultsThe median follow-up for survivors and the median survival (MS) of patients was 23.3 and 18.4 months, respectively. The MS for GBM-molRPA class I, II, and III was 49.7 (95% CI, 22.8–76.6), 19.2 (95% CI, 16.2–22.1), and 13.8 months (95% CI, 11.8–15.4) (P < .001 for all comparisons) in the validation cohort. In the training plus validation cohort, the MS was 58.5 (95% CI, 40.7–76.3), 21. (95% CI, 18.6–23.3), and 14.3 months (95% CI, 12.5–16.1) (P < .001 for all comparisons) for class I, II, and III, respectively. ConclusionThe GBM-molRPA is a valid model. This GBM-molRPA classification can be useful in clinics and guiding patient stratification in future clinical trials.