Proton Therapy in the Treatment of Pediatric Neuroblastoma — A Single-Center Analysis of Acute Treatment-Related Toxicities

Background and Aims: Neuroblastoma (NB) is the most common extracranial solid tumor in pediatric patients.Radiotherapy (RT) plays a key role in the multimodal treatment of intermediate-and high-risk disease.Proton therapy (PT) offers highly conformal dose distributions while minimizing exposure to surrounding healthy tissues, which is particularly relevant in young children.This study aims to evaluate the acute toxicity profile of PT in pediatric patients with NB.Methods: A retrospective analysis was conducted on 16 pediatric patients with intermediate-or high-risk neuroblastoma treated with PT at the National Centre for Oncological Hadrontherapy (CNAO) between 2022 and 2024.Hematological and biochemical parameters (hemoglobin, white blood cells, neutrophils, lymphocytes, platelets, and creatinine) were assessed at four time points: baseline (T0), during treatment (T1), at the end of treatment (T2), and after boost completion (T3).Clinical evaluations were performed weekly.Acute toxicities were graded according to CTCAE v5.0 criteria.Results: All patients were treated using PBS-PT.The median prescribed dose was 21 GyRBE (range 21-36 GyRBE); five patients received a boost to residual disease up to 36 GyRBE.In 75% of cases, the irradiation volume encompassed more than five vertebral bodies.Median age at treatment was 3.3 years (range 1.6-11.6),with a male-to-female ratio of 10:6.Treatment was well tolerated, with no interruptions.Six patients (37.5%) experienced no acute adverse events.Grade 1 radiodermatitis was observed in eight patients, while five patients developed grade 1 gastrointestinal toxicity.No statistically significant changes were detected in hematological or biochemical parameters across the evaluated time points (p > 0.05).Platelet transfusion was required in two patients with pre-existing grade 3 thrombocytopenia.Conclusions: PT appears to be a safe and well-tolerated treatment modality for pediatric NB, with a low incidence of acute toxicity and no treatment interruptions, even in complex cases involving large target volumes.These findings support the use of PT as a valuable radiotherapeutic option in this vulnerable patient population.