Pseudoprogression in pediatric low-grade glioma after irradiation

This study aimed to assess the incidence and management of pseudoprogression after radiation therapy (RT) in patients with pediatric low-grade glioma (LGG). This retrospective review included patients aged 21 years or younger with intracranial LGG treated with curative-intent RT. Pseudoprogression was defined as an increase in tumor size by ≥10% in at least two dimensions between two and three consecutive MR imaging studies. Overall survival (OS) and event-free survival (EFS) were measured from the first day of RT. EFS was defined as survival without true progression or secondary high-grade glioma. Sixty-two of 221 patients developed pseudoprogression, with a 10-year cumulative incidence of 29.0% (95% CI 23.0-35.2). Median time to pseudoprogression was 6.1 months after RT. Symptomatic pseudoprogression was managed with subtotal resection, shunt/Ommaya reservoir placement, or corticosteroids in 11 (18%), 7 (11%), and 2 patients (3%), respectively. The remaining tumors were observed (68%). Patients with pilocytic astrocytoma (PA) had 5.4-fold greater odds of developing pseudoprogression relative to tumors of other histology (odds ratio 95% CI 2.5-11.4, P < 0.0001). Among patients with PA (n = 127), the 10-year cumulative incidence of pseudoprogression was 42.9%. In this group, pseudoprogression was associated with improved 10-year EFS (84.5% vs. 58.5%, P = 0.008) and OS (98.0% vs. 91.2%, P = 0.03). Pseudoprogression after irradiation was common, especially in patients with pilocytic astrocytoma, and was associated with improved survival. Knowledge of the incidence and temporal course of pseudoprogression may help avoid unnecessary salvage therapy.