Extended Volumetric Follow-up of Juvenile Pilocytic Astrocytomas Treated with Proton Beam Therapy

Abstract Purpose: To describe volume changes following proton beam therapy (PBT) for juvenile pilocytic astrocytoma (JPA), we analyzed post-PBT magnetic resonance imaging (MRI) to clarify survivorship, response rate, and the concept of pseudoprogression. Materials and Methods: Pediatric patients with a histologic diagnosis of JPA after a biopsy or subtotal resection and at least 4 post-PBT MRIs were retrospectively reviewed. After PBT, tumors were contoured on follow-up T1-contrasted MRIs, and 3-dimensional volumes were plotted against time, with thresholds for progressive disease and partial response. Patterns of response, pseudoprogression, and progression were uncovered. Post-PBT clinical course was described by the need for further intervention and survivorship. Results: Fifteen patients with a median of 10 follow-up MRIs made up this report: 60% were heavily pretreated with multiple lines of chemotherapy, and 67% had undergone subtotal resection. With a median follow-up of 55.3 months after a median ...