Myeloablative Total Body Irradiation With Volumetric Modulated Arc Therapy for Children-a Single Center Experience

Area of Science:

• Radiation Oncology
• Pediatric Hematology-Oncology
• Stem Cell Transplantation

Background:

• Total body irradiation (TBI) is a crucial part of conditioning therapy for pediatric acute lymphoblastic leukemia (ALL) before allogeneic hematopoietic stem cell transplantation (HSCT).
• Volumetric modulated arc therapy-TBI (VMAT-TBI) was implemented to enhance target conformity and organ-at-risk sparing in TBI delivery.
• This study evaluates the initial institutional experience with VMAT-TBI in pediatric patients.

Purpose of the Study:

• To assess the feasibility and efficacy of VMAT-TBI in pediatric patients with ALL.
• To analyze treatment planning and delivery metrics for VMAT-TBI.
• To evaluate early clinical outcomes and acute toxicities associated with VMAT-TBI.

Main Methods:

• A retrospective review of 10 pediatric patients treated with VMAT-TBI between October 2023 and June 2025.
• Patients received myeloablative conditioning with 12 Gy in 6 fractions over 3 days, followed by etoposide.
• Data collected included treatment planning parameters, delivery times, survival rates, and acute toxicities.

Main Results:

• VMAT-TBI plans achieved excellent target coverage (V100 > 90%) and met organ-at-risk dose constraints (e.g., mean lung dose 8.8 Gy).
• Mean beam-on time was 21.3 minutes per fraction, with image guidance confirming accuracy within 3 mm and <1° rotation.
• One-year overall survival and relapse-free survival were 90%, with 10% nonrelapse mortality. Mucositis (70%) and gastrointestinal toxicities (50% vomiting, 40% diarrhea) were the most common acute toxicities.

Conclusions:

• VMAT-TBI is a safe, feasible, and effective treatment modality for pediatric ALL patients undergoing HSCT.
• The technique provides robust target coverage and an acceptable acute toxicity profile.
• These findings support the implementation of VMAT-TBI, even in resource-limited environments.