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

Purpose: Total body irradiation (TBI) is a critical component of conditioning therapy prior to allogeneic hematopoietic stem cell transplantation in pediatric acute lymphoblastic leukemia. Our institution implemented volumetric modulated arc therapy-TBI (VMAT-TBI) in 2023, aiming to improve target conformity and organ-at-risk sparing using standard linear accelerators. This study describes our initial 2-year institutional experience with VMAT-TBI, focusing on treatment planning and delivery metrics, as well as early clinical outcomes and acute toxicities in pediatric patients. Methods and Materials: We conducted a review of 10 pediatric patients treated with VMAT-TBI at our institution from October 2023 to June 2025. All patients received myeloablative conditioning with 12 Gy in 6 fractions over 3 days, followed by intravenous etoposide preceding allogeneic hematopoietic stem cell transplantation. Data collected included treatment planning parameters, planning duration, delivery times, overall survival, relapse-free survival, and acute toxicities. Results: > 90%) and met organ-at-risk constraints, with mean lung, kidney, and lens doses of 8.8 Gy, 8.7 Gy, and 8.5 Gy, respectively. Mean beam-on time per fraction was 21.3 minutes, and in-room time was 77 minutes. Image guided verification showed that online translation was within 3 mm and