1046 - Hematologic Toxicity, Treatment Completion Time, and Dosimetric Comparison between Proton and Photon Craniospinal Irradiation in Pediatric Tumor Patients: A Propensity Score-Matched Study
Presenter(s)
R. Li1, X. Ding1, D. Meng1, J. Zhu2, and Q. Wang1; 1Shandong Cancer Hospital, Shandong Provincial Key Medical and Health Laboratory of Pediatric Cancer Precision Radiotherapy, Ji Nan, China, 2Shandong Cancer Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China
Purpose/Objective(s): To compare treatment completion time, acute hematologic toxicity, and dosimetric differences between proton and photon radiotherapy in pediatric tumor patients undergoing CSI, and to evaluate the clinical implementation efficiency advantages of proton therapy.
Materials/Methods: Retrospective analysis of 65 patients (proton: 21, photon: 44) after propensity score matching. We compared baseline characteristics, radiotherapy duration, weekly blood counts, and acute toxicity (CTCAE 5.0). Dosimetric parameters (Dmean, V5-V30) were extracted for hematopoietic organs and abdominal structures. Logistic regression identified risk factors for grade =3 toxicity.
Results: Groups were balanced for age, sex, disease status, dose, and chemotherapy (P>0.05). Proton therapy significantly shortened treatment duration (P<0.001). From week 2, platelet counts were higher with protons (P<0.05), with similar trends for leukocytes and neutrophils. Significant differences favored protons for leukopenia (P=0.027), lymphocytopenia (P<0.001), neutropenia (P=0.024), and thrombocytopenia (P=0.001). Grade 3-4 leukopenia occurred in 42.86% (proton) versus 76.74% (photon); 71.43% of proton patients had no thrombocytopenia versus 20.93% with photons, where 20.93% developed grade 3 toxicity. Photon therapy independently predicted grade =3 toxicity (OR=6.38, 95%CI:0.75-23.35, P=0.005). Dosimetrically, protons significantly reduced spinal V20+, skull V30+, thoracic/pelvic V5-V10, and abdominal organ doses (P<0.01).
Conclusion: Proton craniospinal irradiation significantly reduces the irradiated volume of hematopoietically active bone marrow regions and abdominal organs through the Bragg peak physical characteristics substantially lowering the risk of acute hematologic toxicity while significantly shortening total radiotherapy duration and improving treatment completion efficiency. This dual advantage supports the priority use of proton therapy in pediatric tumor patients requiring craniospinal irradiation to reduce long term toxicities and improve treatment quality.