Long-term outcomes after irradiation (RT) for pediatric low-grade glioma.

Abstract

10549 Background: Treatment for pediatric low-grade glioma (LGG) is variable, depending on age and tumor location. Systemic therapy (ST) is often used to delay RT, but ST does not result in durable local control. The goal of this study was to evaluate event-free survival (EFS) and toxicities for pediatric LGG treated with RT over a 30-year period. Methods: All patients age ≤21 with intracranial pediatric LGG (WHO grade I-II) treated with RT at a single institution since May 1986 were included in this retrospective review. Patients with metastatic disease (M+) received craniospinal irradiation (CSI); otherwise, RT was conformal. EFS and overall survival (OS) were measured from the first day of RT. Events included death, progression, or secondary high-grade glioma. Results: 221 patients were eligible. Median follow-up was 11.3 yrs (range, 0.1-30.5). Median RT dose was 54 Gy. 10-yr EFS and OS were 67.9% (95% CI 60.4-74.3) and 91.1% (95% CI 85.8-94.5) for non-metastatic patients, respectively. For 12 M+ patients treated with CSI, 10-yr EFS and OS were 58.9% (95% CI 23.4-82.5) and 70.0% (32.9-89.2), respectively. 28.6% developed pseudoprogression (PP) with median time to onset and resolution of 6.1 months (IQR 3.6-14.6) and 6.4 months (IQR 3.5-11.7), respectively. Patients with PP had improved 10-yr EFS (83.4% vs. 61.0%, HR 0.40, p = .006). Patients with grade II tumors and who received pre-RT ST had lower EFS (Table). Sex, NF-1, tumor location, extent of surgery and CSI were not independently associated with EFS. 10-yr cumulative incidence of grade ≥2 vasculopathy was 7.5% (95% CI 4.9-11.4). There were 12 cases of secondary high-grade glioma, with a 20-yr cumulative incidence of 5.5% (95% CI 2.6-11.4). Conclusions: Irradiation provides long-term control of pediatric LGG in a majority of patients. Receipt of pre-RT systemic therapy was associated with reduced EFS; this association requires further investigation. [Table: see text]