Toxicity and Clinical Results after Proton Therapy for Pediatric Medulloblastoma: A Multi-Centric Retrospective Study

SIMPLE SUMMARY: Medulloblastoma is the most common malignant brain tumor in children. Treatment is effective, but survivors often develop long-term sequelae that impact their quality of life. Proton therapy has similar efficacy as traditional radiotherapy but might achieve lower toxicity. We present our retrospective results on 43 children treated with active scanning proton therapy for medulloblastoma. This case series confirms that protons for medulloblastoma are associated with a favorable toxicity profile. Results on late effects and survival, although preliminary, are encouraging. ABSTRACT: Medulloblastoma is the most common malignant brain tumor in children. Even if current treatment dramatically improves the prognosis, survivors often develop long-term treatment-related sequelae. The current radiotherapy standard for medulloblastoma is craniospinal irradiation with a boost to the primary tumor site and to any metastatic sites. Proton therapy (PT) has similar efficacy compared to traditional photon-based radiotherapy but might achieve lower toxicity rates. We report on our multi-centric experience with 43 children with medulloblastoma (median age at diagnosis 8.7 years, IQR 6.6, M/F 23/20; 26 high-risk, 14 standard-risk, 3 ex-infant), who received active scanning PT between 2015 and 2021, with a focus on PT-related acute-subacute toxicity, as well as some preliminary data on late toxicity. Most acute toxicities were mild and manageable with supportive therapy. Hematological toxicity was limited, even among HR patients who underwent hematopoietic stem-cell transplantation before PT. Preliminary data on late sequelae were also encouraging, although a longer follow-up is needed.