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.
calibrations were constructed for all the tube voltages. All HU images and direct ED images were imported into a treatment planning system, where all HU images were assigned the corresponding CT calibration curves while all direct ED images were assigned a linear CT calibration curve. A cylindrical planning target volume of 5 cm in diameter was planned to receive full prescription dose from 9 coplanar beams on all images. Gamma analysis was performed to demonstrate dosimetric change quantitatively. Results: The deviation of ED obtained from the direct ED images was -0.4%AE1.7% from the true values for all inserts, slightly better than that from the HU images, which was determined to be -0.7%AE1.8%. Gamma analysis on intercomparison between the direct ED images and the HU images acquired at the same tube voltage indicated negligible difference with lowest passing rate at 99.9%. Gamma analysis on cross-comparison among the direct ED images acquired at various voltages indicated negligible inherent variation with lowest passing rate at 99.1%, slightly better than the lowest passing rate of 99.0% scored on cross-comparison among the HU images acquired at various tube voltages. Conclusion: Direct ED images require no CT calibration while showing equivalent dosimetry, regardless of tube voltages, compared to that obtained from standard HU images. The ability of acquiring direct ED images simplifies the current practice at a safer level by eliminating CT calibration and HU conversion from commissioning and treatment planning, respectively. Furthermore, it unlocks a wider range of tube voltages in CT scanner for better imaging quality while maintaining similar dosimetric accuracy.Purpose/Objective(s): Traditional radiation therapy inverse planning relies on the weighting factors to subjectively balance the conflicting criteria for different structures. The resulting manual trial-and-error determination of the weighting factors has long been recognized as the most timeconsuming part of treatment planning. The purpose of this work is to develop a novel inverse planning framework that parameterizes the dosimetric tradeoff among the structures with physically more meaningful quantities to simplify the search for a clinically sensible plan.Materials/Methods: A permissible dosimetric uncertainty is introduced for each of the structures to balance their conflicting dosimetric requirements. For simplicity, the uncertainty of a structure is extracted from a library of previous cases that possess similar anatomy and prescription. The inverse planning is then formulated into a convex feasibility problem with the goal of generating plans with acceptable dosimetric uncertainties. A sequential procedure (SP) is derived to simultaneously tune and solve the model. In SP, the feasibility problem is reduced to 3 submodels to contain the uncertainty in the planning target volume (PTV), the critical structures, and all other structures to spare, respectively. The proposed technique is applied to plan a liver case and a head-and-neck case in...
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.
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