Survival Outcomes With Short-Course Radiation Therapy in Elderly Patients With Glioblastoma: Data From a Randomized Phase 3 Trial

Purpose To perform a subset analysis of survival outcomes in elderly patients with glioblastoma from a randomized phase 3 trial comparing 2 short-course radiation therapy (RT) regimens in elderly and/or frail patients. Methods and Materials The original trial population included elderly and/or frail patients with a diagnosis of glioblastoma. Patients joined the phase 3, randomized, multicenter, prospective, noninferiority trial; were assigned to 1 of 2 groups in a 1:1 ratio, either short-course RT (25 Gy in 5 fractions, arm 1) or commonly used RT (40 Gy in 15 fractions, arm 2); and were stratified by age (<65 years and ≥65 years), Karnofsky Performance Status (KPS), and extent of surgery. For the subset analysis in this study, only patients aged ≥65 years were evaluated (elderly and frail patients were defined as patients aged ≥65 years with KPS of 50%-70%; elderly and non-frail patients were defined as patients aged ≥65 years with KPS of 80%-100%); 61 of the 98 initial patients comprised the patient population, with 26 patients randomized to arm 1 and 35 to arm 2. Results In this unplanned analysis, the short-course RT results were not statistically significantly different from the results of commonly used RT in elderly patients. The median overall survival time was 6.8 months (95% confidence interval [CI], 4.5-9.1 months) in arm 1 and 6.2 months (95% CI, 4.7-7.7 months) in arm 2 (P=.936). The median progression-free survival time was 4.3 months (95% CI, 2.6-5.9 months) in arm 1 and 3.2 months (95% CI, 0.1-6.3 months) in arm 2 (P=.706). Conclusions A short-course RT regimen of 25 Gy in 5 fractions is an acceptable treatment option for patients aged ≥65 years, mainly those with a poor performance status or contraindication to chemotherapy, which would be indicated in cases of methylated O6 methylguanine-DNA-methyltransferase promoter tumors.