Radt-24. phase ii study of proton radiation therapy for lower grade gliomas

Abstract PURPOSE To report preliminary results on outcomes of patients with lower grade gliomas (LGG) treated with proton therapy. METHODS Patients with grade II or IDH mutant grade III glioma and indications for radiation therapy were enrolled in a prospective single arm trial of proton therapy (PRT), receiving a dose of 54 Gy(RBE) or 59.4 Gy(RBE), respectively. Comprehensive baseline and regular post-treatment evaluations of neuroendocrine function, neurocognitive functions (NCF), quality of life (QOL), and progression-free survival (PFS) were performed. RESULTS Among 60 patients (median age 40.8) who received PRT, 28 (47%) were men, and 39 (65%) were WHO grade II. Eighteen patients (30%) were IDH mutant+1p/19q co-deleted, 36 (60%) were IDH mutant astrocytoma, and 6 (10%) were IDH wildtype. Treatment was at initial diagnosis (41; 68%) or progression (19; 32%). Median follow-up after PRT was 4.1 years. All current data are reported for 3 years from PRT. PFS at 3 years was 86% for all patients, 84% for grade II (n = 39), and 90% for favorable grade III gliomas (n = 21). PFS was 83% for IDH mutant astrocytoma, and 94% for IDH mutant+1p/19q co-deleted oligodendrogliomas. New endocrine dysfunction was detected in 3 patients (5%). There was one grade 4 case of brain necrosis (2%) but no grade 3 toxicities. NCF decline, defined by Z-score drop of >/= 1SD on clinical trials battery composite, occurred in 7% (n = 3/43). QOL assessment by FACT-Brain showed 16% with decline of >/= 10 points (n = 7/43). CONCLUSIONS At 3 years post-treatment, LGG patients receiving PRT have a high PFS, similarly to previous reports on photon therapy, few new neuroendocrine deficiencies, modest treatment toxicities, and minimal decline in NCF or QOL. These positive outcomes may be attributable to limited integral dose to the brain by use of PRT, demonstrating its value in treatment of LGG patients with long survival expectations.