Proton therapy for low-grade gliomas: Results from a prospective trial

Abstract

Background: In this prospective study, the authors evaluated potential treatment toxicity and progression-free survival in patients with low-grade glioma who received treatment with proton radiation therapy.

Methods: Twenty patients with World Health Organization grade 2 glioma who were eligible for radiation therapy were enrolled in a prospective, single-arm trial of proton therapy. The patients received proton therapy at a dose of 54 Gy (relative biological effectiveness) in 30 fractions. Comprehensive baseline and regular post-treatment evaluations of neurocognitive function, neuroendocrine function, and quality of life (QOL) were performed.

Results: All 20 patients (median age, 37.5 years) tolerated treatment without difficulty. The median follow-up after proton therapy was 5.1 years. At baseline, intellectual functioning was within the normal range for the group and remained stable over time. Visuospatial ability, attention/working memory, and executive functioning also were within normal limits; however, baseline neurocognitive impairments were observed in language, memory, and processing speed in 8 patients. There was no overall decline in cognitive functioning over time. New endocrine dysfunction was detected in 6 patients, and all but 1 had received direct irradiation of the hypothalamic-pituitary axis. QOL assessment revealed no changes over time. The progression-free survival rate at 3 years was 85%, but it dropped to 40% at 5 years.

Conclusions: Patients with low-grade glioma tolerate proton therapy well, and a subset develops neuroendocrine deficiencies. There is no evidence for overall decline in cognitive function or QOL.

Keywords: late effects; low-grade glioma; neurocognitive function; neuroendocrine function; pituitary function; proton radiation; proton therapy; quality of life.