# Evaluating the Feasibility and Safety of Daily Inter-facility Travel for Proton Beam Therapy During Chemotherapy-Induced Myelosuppression in Children With Cancer

## TL;DR

This study examines the safety and feasibility of daily travel for proton beam therapy in children with cancer during myelosuppression, finding it generally safe with comparable infection risks to conventional therapy.

## Contribution

The study provides empirical evidence supporting the safety of inter-facility proton beam therapy during myelosuppression in pediatric oncology.

## Key findings

- Daily inter-facility travel for PBT during myelosuppression was feasible with no travel-related adverse events.
- Infectious outcomes were comparable between PBT and XRT groups despite more frequent treatment interruptions in PBT.
- No significant differences in febrile neutropenia or documented infections were observed between the two treatment groups.

## Abstract

Introduction: Proton beam therapy (PBT) is widely used in pediatric oncology to reduce radiation exposure to normal tissues and mitigate late adverse effects. In Japan, the limited availability of centers that can provide pediatric PBT with sedation and/or concurrent chemotherapy often necessitates inter-facility travel. However, the safety of daily inter-facility travel for PBT during chemotherapy-induced myelosuppression has not been well evaluated. We assessed the feasibility and safety of this model in Nagano Prefecture.

Methods: We conducted a retrospective cohort study using data from three hospitals in Nagano Prefecture (Nagano Children’s Hospital, Shinshu University Hospital, and Aizawa Hospital) from June 2011 to August 2021. Patients who underwent PBT at a proton center with daily inter-facility travel during chemotherapy-induced myelosuppression were compared with patients who received conventional X-ray therapy (XRT) without transfer. Myelosuppression was defined as an absolute neutrophil count <500/µL. We extracted data on infection prophylaxis, febrile neutropenia (FN), documented infections, radiotherapy interruptions, and other adverse events, including events related to inter-facility travel or sedation.

Results: Among 166 pediatric patients who received radiotherapy, 55 underwent PBT and 111 underwent XRT. Of these, 20 patients in the PBT group and 18 in the XRT group developed myelosuppression during concurrent chemoradiotherapy and were included in the analysis. Treatment interruptions were more frequent in the PBT group, but most lasted one to two days. FN was the most common immediate reason for interruption. There were no significant differences between groups in the incidence of FN or documented infections, and no adverse events were clearly attributable to inter-facility travel or sedation in the PBT group.

Conclusions: In this cohort, daily inter-facility travel for pediatric PBT during chemotherapy-induced myelosuppression was feasible. Although brief treatment interruptions were more frequent in the PBT group, infectious outcomes were comparable to those of patients receiving XRT without transfer, and no travel- or sedation-related adverse events were identified. Coordinated multidisciplinary protocols may help minimize avoidable interruptions while maintaining safety.