ACTR-72. A PROSPECTIVE PHASE II RANDOMIZED TRIAL TO COMPARE INTENSITY MODULATED PROTON RADIOTHERAPY (IMPT) VS. INTENSITY MODULATED RADIOTHERAPY (IMRT) FOR NEWLY DIAGNOSED GLIOBLASTOMA (GBM)

Abstract

PURPOSE: To determine if IMPT compared to IMRT delayed time to cognitive failure in patients with newly diagnosed GBM. METHODS: Eligible patients were randomized to IMPT vs. IMRT. Randomization was stratified for RPA class (III‐IV vs. V), Mini Mental Status Examination score (21‐26 vs. 27‐30) and age (< 65 vs. 65 or older). The primary endpoint was time to cognitive failure on any of the 6 cognitive outcomes (HVLT‐R, TMT, COWA) with failure defined as a decline that met or exceeded the reliable change index (RCI). RESULTS: A total of 90 patients were enrolled (45 per arm) and 75 were evaluable with median follow‐up of 14.5 (0.1, 32.1) months; median of 7.0 (0.1, 25.4) months for IMPT (n=32) vs. 25.6 (1.5, 32.1) months for IMRT (n=43). There were no differences in sociodemographic characteristics or baseline cognitive function between arms. Time to cognitive failure was shorter in the IMPT arm vs. the IMRT arm (p<0.05) and cumulative incidence of cognitive deterioration at 4 months was 0.593 (0.378, 0.755) IMPT vs. 0.372 (0.224, 0.52) IMRT. The number of grade 2 or higher toxicities were greater in patients who received IMRT (n=21) vs. IMPT (n=9). CONCLUSIONS: Preliminary results of this study suggest IMPT is not associated with a delay in time to cognitive failure but did reduce toxicity. Additional evaluation of the impact of tumor location and volume, radiation dosimetry, and tumor molecular subtypes on cognition is ongoing. Larger randomized trials are needed to determine the impact of IMPT vs. IMRT on GBM tumor control and survival.