Abstract
Cancer of the brain and central nervous system (CNS) is the second most common of all pediatric cancers. Treatment of many of these cancers includes radiation therapy of which radiation induced cerebral necrosis (RICN) can be a severe and potentially devastating side effect. Risk factors for RICN include brain volume irradiated, the dose given per fraction and total dose. Thirteen pediatric patients were selected for this study to determine the difference in predicted risk of RICN when treating with volumetric modulated arc therapy (VMAT) compared to passively scattered proton therapy (PSPT) and intensity modulated proton therapy (IMPT). Plans were compared on the basis of dosimetric endpoints in the planned treatment volume (PTV) and brain and a radiobiological endpoint of RICN calculated using the Lyman-Kutcher-Burman probit model. Uncertainty tests were performed to determine if the predicted risk of necrosis was sensitive to positional errors, proton range errors and selection of risk models. Both PSPT and IMPT plans resulted in a significant increase in the maximum dose to the brain, a significant reduction in the total brain volume irradiated to low doses, and a significant lower predicted risk of necrosis compared with the VMAT plans. The findings of this study were upheld by the uncertainty analysis.
Highlights
Cancer of the brain and central nervous system (CNS) is the second most common of all pediatric cancers
The Surveillance Epidemiology and End Result (SEER) program reported that astrocytomas and other gliomas make up approximately 67% of pediatric brain cancers, and ependymomas make up 9% [2]
The intensity modulated proton therapy (IMPT) plans resulted in significantly better conformity than the volumetric modulated arc therapy (VMAT) plans with an average conformity index (CI) value of 0.83 ± 0.06
Summary
Cancer of the brain and central nervous system (CNS) is the second most common of all pediatric cancers. The Surveillance Epidemiology and End Result (SEER) program reported that astrocytomas and other gliomas make up approximately 67% of pediatric brain cancers, and ependymomas make up 9% [2]. Treatment for these tumors often incorporates radiation therapy and/or chemotherapy [3] with typical prescriptions of 50–60 Gy in 1.8–2Gy/fraction to the planned treatment volume (PTV) [4]. The potential side effects from CNS irradiation can include acute effects and late effects. Acute affects are seen early and can include alopecia, erythema, otitis, tinnitus, or even temporary demyelination [3]
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