Volumetric de‐escalation and improved acute toxicity with proton craniospinal irradiation using a vertebral body‐sparing technique

Abstract

Purpose: In growing children, craniospinal irradiation (CSI) has historically treated the entire vertebral body (VB) to avoid potential long-term spinal abnormalities. Vertebral body-sparing proton craniospinal irradiation (VBSpCSI) is a technique that spares the majority of the VB from significant irradiation, and long-term safety outcomes have been reported previously. This retrospective study reviews the acute toxicity profile of children treated with VBSpCSI in a cohort comparison with photon-based craniospinal radiotherapy (3DCRT). Methods: Thirty-eight pediatric CSI patients treated between 2008 and 2018 were retrospectively evaluated for treatment-related toxicity. Acute toxicity outcomes and acute hematologic profiles were compared according to treatment modality, either VBSpCSI or 3DCRT. Statistical analysis was performed using Fisher's exact test for toxicity.Results: Twenty-five patients received VBSpCSI and 13 patients received photon CSI.Mean patient age at treatment was 7.5 years (range 2-16). The cohorts were well matched with respect to gender, age, and CSI dose. Patients receiving VBSpCSI had lower rates of grade 2+ gastrointestinal (GI) toxicity (24% vs. 76.5%, p = .005), grade 2+ nausea (24% vs. 61.5%, p = .035), and any-grade esophagitis (0% vs. 38%, p = .0026).Patients treated with VBSpCSI had lower red blood cell transfusion rates (21.7% vs. 60%, p = .049) and grade 4+ lymphopenia (33.3% vs. 77.8%, p = .046).Conclusions: VBSpCSI in children is a volumetric de-escalation from traditional volumes, which irradiate the entire VB to full or intermediate doses. In our study, VBSpCSI was associated with lower rates of acute GI and hematologic toxicities. Long-term growth outcomes and disease control outcomes are needed for this technique.

Late-onset lymphopenia during radiation is associated with an increased risk of tumor recurrence in newly-diagnosed pediatric medulloblastoma

“…However, there is increasing awareness that proton beam RT may induce less lymphopenia than photons. [25][26][27] When proton vertebral body sparing techniques are utilized for CSI, which in our cohort occurred for skeletally mature patients, data shows that lymphopenia is lessened 28,29 , as the vertebral bodies contain >25% of the total bone marrow. 30 The majority of our patients had their entire vertebral body covered by the CSI dose due to receiving photon beam RT or being skeletally immature during proton beam RT.…”

Late‐onset lymphopenia during radiation is associated with an increased risk of tumor recurrence in newly diagnosed pediatric medulloblastoma

“…However, there is increasing awareness that proton beam RT may induce less lymphopenia than photons 13–15 . When proton vertebral body‐sparing techniques are utilized for CSI, which in our cohort occurred for skeletally mature patients, data show that lymphopenia is lessened, 16,17 as the vertebral bodies contain more than 25% of the total bone marrow 18 . The majority of our patients (77/79, 97%) had their entire vertebral body covered by the CSI dose due to receiving photon beam RT (38 patients) or being skeletally immature during proton beam RT (39/41 patients); only two skeletally mature patients (one male, one female) treated with proton beam RT had their anterior vertebral bodies spared.…”

“…However, there is increasing awareness that proton beam RT may induce less lymphopenia than photons. [13][14][15] When proton vertebral body-sparing techniques are utilized for CSI, which in our cohort occurred for skeletally mature patients, data show that lymphopenia is lessened, 16,17 as the vertebral bodies contain more than 25% of the total bone marrow. 18 The majority of our patients (77/79, 97%)…”