Clinical outcomes and late endocrine, neurocognitive, and visual profiles of proton radiation for pediatric low-grade gliomas.

Purpose/objective(s): Primary low-grade gliomas are common brain tumors of childhood, many of which require radiation therapy (RT) as definitive treatment. Increased conformality of RT could decrease the incidence and severity of late effects. We report our experience with 32 pediatric patients treated with proton RT.

Methods And Materials: Thirty-two pediatric patients with low-grade gliomas of the brain or spinal cord were treated with proton RT from 1995 to 2007. Sixteen patients received at least 1 regimen of chemotherapy before definitive RT. The median radiation dose was 52.2 GyRBE (48.6-54 GyRBE).

Results: The median age at treatment was 11.0 years (range, 2.7-21.5 years), with a median follow-up time of 7.6 years (range, 3.2-18.2 years). The 6-year and 8-year rates of progression-free survival were 89.7% and 82.8%, respectively, with an 8-year overall survival of 100%. For the subset of patients who received serial neurocognitive testing, there were no significant declines in Full-Scale Intelligence Quotient (P=.80), with a median neurocognitive testing interval of 4.5 years (range, 1.2-8.1 years) from baseline to follow-up, but subgroup analysis indicated some significant decline in neurocognitive outcomes for young children (<7 years) and those with significant dose to the left temporal lobe/hippocampus. The incidence of endocrinopathy correlated with a mean dose of ≥40 GyRBE to the hypothalamus, pituitary, or optic chiasm. Stabilization or improvement of visual acuity was achieved in 83.3% of patients at risk for radiation-induced injury to the optic pathways.

Conclusions: This report of late effects in children with low-grade gliomas after proton RT is encouraging. Proton RT appears to be associated with good clinical outcome, especially when the tumor location allows for increased sparing of the left temporal lobe, hippocampus, and hypothalamic-pituitary axis.