Volumetric De-Escalation and Improved Acute Toxicity with Proton
Craniospinal Irradiation Using a Vertebral Body Sparing Technique
Abstract
Purpose: Craniospinal irradiation (CSI) has historically treated the
entire vertebral body (VB) in growing children. Vertebral body sparing
proton craniospinal irradiation (VBSpCSI) is a technique which spares
the majority of the VB from significant irradiation. This retrospective
study reviews the acute toxicity of VBSpCSI compared to photon CSI.
Methods: Pediatric CSI patients treated between 2008 and 2018 were
evaluated. Patients were stratified to the VBSpCSI cohort or the photon
cohort and analyzed for acute toxicity profile during treatment and
disease-free survival (DFS). Statistical analysis was performed using
Kaplan-Meier log rank analysis for DFS and Fisher’s exact test for
toxicity. Results: Twenty-five patients received VBSpCSI and 13 patients
received photon CSI. Mean patient age at treatment was 7.5y (range 2 to
16). The cohorts were well-matched with respect to gender, age, and CSI
dose. Two-year DFS was similar between cohorts (81% VBSpCSI vs 61%
photon, p=0.18). Patients receiving VBSpCSI had lower rates of grade 2+
GI toxicity (24% vs 76.5%, p=0.005), grade 2+ nausea (24% vs 61.5%,
p=0.035), and any-grade esophagitis (0% vs 38%, p=0.0026). Patients
treated with VBSpCSI had lower red blood cell transfusion rates (21.7%
vs 60%, p=0.049) and grade 4+ lymphopenia (33.3% vs 77.8%, p=0.046).
Conclusions: VBSpCSI in children is a volumetric de-escalation from
traditional volumes which irradiate the entire vertebral body. Based on
our results, VBSpCSI was associated with less acute gastrointestinal and
hematologic toxicity. The study adds to the growing body of evidence
supporting the use of protons over photons for pediatric CSI.