2455 - Safety and Efficacy of Photon Re-Irradiation with Whole Brain Radiotherapy or Craniospinal Irradiation for Recurrent Pediatric Central Nervous System Malignancies
Presenter(s)
P. P. Patel1, H. Elhalawani2, K. J. Marcus2, D. A. Haas-Kogan3, and K. X. Liu2; 1Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, Boston Children's Hospital, Harvard Medical School, Boston, MA, 2Department of Radiation Oncology, Mass General Brigham, Harvard Medical School, Boston, MA, 3Brigham and Women's Hospital and Dana-Farber Cancer Institute/ Harvard, Boston, MA, Boston, MA
Purpose/Objective(s): With continued advancements in treatment for patients with recurrent pediatric central nervous system (CNS) malignancies, photon re-irradiation with whole brain radiotherapy (WBRT) or craniospinal irradiation (CSI) remains an option, but few studies have investigated the safety and outcome of this approach. Our study aims to characterize clinical outcomes, including toxicity, and correlate outcomes with dosimetric parameters.
Materials/Methods: This single-institution retrospective study was approved by the IRB. Inclusion criteria was <21 years at diagnosis, received definitive focal RT or CSI at initial diagnosis, and received either WBRT or CSI as part of treatment at relapse or secondary malignancy from 2013-2024. Patients with <1 month of follow-up were excluded. Clinical and treatment characteristics were recorded. Kaplan-Meier method and log-rank test were used to assess overall survival (OS) and progression-free survival (PFS). Toxicity was graded using CTCAE v5.
Results: Of the 15 patients in the cohort, 6 (40%) were female. Median age at diagnosis was 7.3 years (range: 3.1-17.0). The most common diagnoses were medulloblastoma (n=6) and high-grade glioma (n=3). At diagnosis, 11 patients received CSI and 4 patients received focal RT. The median dose for first RT was 54 Gy/GyRBE (range: 21.6-59.4) and 12 patients received proton RT at diagnosis. Median time to first relapse was 18.4 months (range: 3.2-94.8). Location of first recurrence was brain (n=5), spine (n=3), or both brain and spine (n=7). Nine patients received chemotherapy and seven received additional radiotherapy before re-CSI/re-WBRT. All patients had progression noted =2 times radiographically prior to re-CSI/reWBRT. Eight patients received re-CSI and 7 received re-WBRT with median dose of 30 Gy including simultaneously integrated or sequential boost (range: 20-54 Gy). Median dose of re-CSI or re-WBRT was 24 Gy (range: 18-30.6). Median cumulative doses to the brain, brainstem, optic chiasm, left optic nerve, right optic nerve, and spinal cord were 88.4 Gy (range: 60.1-112.7), 79.9 Gy (range: 58.3-111.4), 57.6 Gy (range: 43.8-104.2), 54.8 Gy (range: 32.7-80.3), 56.1 Gy (33.4-64.7), 57.7 Gy (range: 25-79.5), respectively. Median follow-up after re-CSI/re-WBRT was 8.4 months (range: 1.6-88.4 months), and PFS and OS at 8 months was 31.7% and 72.2%, respectively. For 5 patients, areas of prior RT were purposely undercovered during re-CSI/re-WBRT and 4 of those patients had recurrences within the underdosed areas. Two patients are without evidence of disease at 5.1 months and 88.4 months after re-CSI. No grade =2 CNS toxicity was observed.
Conclusion: Re-CSI/re-WBRT can be a safe option and provide local control, but the median follow-up time remains short and cumulative doses to critical organs at risk remain important considerations for this approach. Future prospective studies are needed to further characterize safety and efficacy of re-CSI/re-WBRT for pediatric patients with recurrent CNS disease.