Modern Radiation Treatment Planning Parameters and Outcomes in Pediatric Tectal Gliomas

Abstract

Purpose: Pediatric low-grade tectal gliomas are rare, indolent tumors of the brain stem. We reviewed outcomes of pediatric patients who received a diagnosis of low-grade tectal gliomas and report dosimetric parameters for those receiving radiation therapy (RT). Methods and Materials: We retrospectively reviewed all pediatric patients (age <18 years) at our institution diagnosed with a low-grade glioma between 1993 and 2020 (n = 288). Twenty-three patients with tectal gliomas were identified. Patients who received RT (n = 8) had detailed dosimetric analyses performed. Doses to critical structures and any resulting toxicities were reviewed. Minimum follow-up was 2 years and complete follow-up was available for all patients. Results: Twenty-three patients, with a median age of 8.9 years, were included (range, 0.5-16.2 years). At a median follow-up of 7.4 years (range, 2-24 years), all were alive at the end of the study period. Three patients (13%) were treated with upfront RT; none of these patients developed local failure (LF) after a median follow-up of 10.6 years. One patient was treated with upfront chemotherapy with no evidence of progression afterward. Nineteen patients were initially observed after diagnosis and 26% of them (n = 5) experienced local progression. All 5 were treated with salvage RT, with 1 patient requiring further treatment with chemotherapy. Fractionation schedules for patients undergoing upfront or salvage RT included 50.4 Gy in 28 fractions (n = 4), 54 Gy in 30 fractions (n = 2), and 51 Gy in 30 fractions (n = 2). For patients treated after 2007, the gross tumor volume was delineated on a T2 magnetic resonance imaging with an average gross tumor volume-to-planning target volume expansion of 4.5 mm (range, 3-5 mm). Detailed dosimetric parameters were available for all patients treated with RT. Conclusions: Our review supports the indolent behavior for most tectal gliomas. For the subset of tumors with evidence of progression, modern photon RT results in excellent oncologic outcomes with minimal late effects.