Effects of vertebral-body-sparing proton craniospinal irradiation on the spine of young pediatric patients with medulloblastoma

Abstract

PurposeTo investigate the long-term effects of vertebral-body-sparing proton craniospinal irradiation (CSI) on the spine of young patients with medulloblastoma.Methods and materialsSix children between the ages of 3 and 5 years with medulloblastoma were treated with vertebral-body-sparing proton CSI after maximal safe resection. Radiation therapy was delivered in the supine position with posterior beams targeting the craniospinal axis, and the proton beam was stopped anterior to the thecal sac. Patients were treated with a dose of either 23.4 Gy or 36 Gy to the craniospinal axis followed by a boost to the posterior fossa and any metastatic lesions. Chemotherapy varied by protocol. Radiographic effects on the spine were evaluated with serial imaging, either with magnetic resonance imaging scans or plain film using Cobb angle calculations, the presence of thoracic lordosis, lumbar vertebral body-to-disc height ratios, and anterior-posterior height ratios. Clinical outcomes were evaluated by patient/family interview and medical chart review.ResultsOverall survival and disease free survival were 83% (5/6) at follow-up. Median clinical and radiographic follow-up were 13.6 years and 12.3 years, respectively. Two patients were clinically diagnosed with scoliosis and treated conservatively. At the time of follow-up, no patients had experienced chronic back pain or required spine surgery. No patients were identified to have thoracic lordosis. Diminished growth of the posterior portions of vertebral bodies was identified in all patients, with an average posterior to anterior ratio of 0.88, which was accompanied by compensatory hypertrophy of the posterior intervertebral discs.ConclusionVertebral-body-sparing CSI with proton beam did not appear to cause increased severe spinal abnormalities in patients treated at our institution. This approach could be considered in future clinical trials in an effort to reduce toxicity and the risk of secondary malignancy and to improve adult height.

<p>Outcome and prognostic factors following palliative craniospinal irradiation for leptomeningeal carcinomatosis</p>

“…Regarding field junctions, different techniques have been conceived to compensate for the positioning errors and avoid relevant over- or underdosage: exploiting the advantages of IMRT, low-gradient junction techniques, as well as non-coplanar IMRT techniques were proven effective dosimetrically 50,51. Superior sparing of bone marrow in the vertebral bodies, as well as even higher dose conformity can be achieved using proton irradiation 29,52. Favorable results regarding toxicity and tumor control have been described for proton CSI in pediatric tumors in several recent works, although proton therapy generally reintroduces the issue of field junctions 53–55…”

Updates in the management of intradural spinal cord tumors: a radiation oncology focus

“…63,64 This treatment delivery will also have the potential to reduce the risk of late treatment-related toxicities, such as radiation-induced malignancies. 65,66 A B C Fig. 5 Sagittal planning CT scans of (A) a patient undergoing craniospinal irradiation using multiple abutting conventional radiotherapy fields, (B) helical arc delivery technique, or (C) pencil beam scanning proton therapy with radiotherapy isodose lines illustrated for each treatment type.…”

Irradiating Residual Disease to 30 Gy with Proton Therapy in Pediatric Mediastinal Hodgkin Lymphoma

“…Although higher doses of RT have been avoided in PHL to limit late effects, the greatest concern is OAR dose. Mean heart and lung doses of 10 and 12 Gy [9,10], respectively, are considered reasonably tolerable, whereas doses of 18 to 20 Gy to the bone can stunt growth [11]. Our results demonstrate that higher RT doses to the target can be delivered while reducing the dose to the OARs with a smaller target volume, as with the rISRT 30Gy plan.…”