Survival, late toxicity and ability to return to work after proton radiotherapy for low-grade gliomas

PURPOSE: Level I evidence to inform decisions on radiation modality and chemotherapy regimen choice in adult-type diffuse gliomas CNS WHO grade 2 are awaited. The retrospective analysis was performed to assess overall survival (OS), progression-free survival (PFS) and late toxicity including ability to return to work in 2016 CNS WHO grade 1 and grade 2 gliomas (low-grade gliomas [LGG]) patients treated with intensity modulated proton beam radiotherapy (IMPT). METHODS: Patients with 2016 CNS WHO LGG after surgery, treated with IMPT at our institution from 2016 to 2021 were eligible for this analysis. Data were retrospectively collected from medical and imaging records. RESULTS: 143 patients were identified. Diffuse astrocytoma isocitrate dehydrogenase (IDH) mutant was the predominant phenotype. Median follow-up was 66.5 months. Five-year OS and PFS were 78.21%, 76.52%, 85.92% and 80.34%, 65.59%, 86.07% for the whole cohort, diffuse astrocytoma IDH mutant and gemistocytic astrocytoma combined, and oligodendroglioma IDH mutant 1p19q codeleted respectively. Mean residual tumor volume was 61.3 cm³ and mean planning target volume (PTV) was 335.7 cm³. At 12, 36 and 60 months after IMPT 61 (42.66%), 61 (42.66%) and 59 (41.26%) patients held down in full-time employment. Each additional cubic centimeter of PTV significantly reduced ability to return to the initial full-time work by 0.5% (Odds Ratio [OR] = 0.995, p = 0.046). 4 cases of CTCAE grade 3 late toxicity were reported (2 cases of optic neuropathy, 1 late fatigue, and 1 muscle weakness). CONCLUSIONS: Irradiation brain volume is associated with maintaining ability to work.