SU‐E‐T‐43: Calculation of the Risks of Second Cancer and Cardiac Toxicities for a Pediatric Patient Treated with Photon and Proton Radiotherapies

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Conference Proceeding

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Purpose: Although advanced radiation treatment methods deliver highly conformal primary dose, they will expose patients to stray radiation doses, which increases patients' risks of radiation‐induced late effects. Second cancer and cardiac toxicity, two chief late effects of concern, can be physically and psychologically devastating to patients that survive their first cancer. There are limited comparative studies about second cancer risk for patients following photon and proton craniospinal irradiation (CSI), and there is a lack of predicted risk of cardiac toxicities for those patients. The purpose of this work was to calculate the risks of second cancer and cardiac toxicities after receiving photon and proton CSI therapies, based on realistic patient data, accurate dose calculation and latest dose‐response models. Methods: Treatment plans were created for both modalities for a pediatric patient with medulloblastoma. The risks of second cancer for radiosensitive organs and normal tissue complication probabilities (NTCP) for the heart sub‐structures were calculated using existing models and dose volume histograms (DVH) from commercial treatment planning system (TPS). Primary doses were taken from TPS directly, and stray radiation doses were obtained from measurements or Monte Carlo simulations. Sensitivity tests were carried out to test the sensitivity of the final results to the changes of dose‐risk relationship, NTCP model parameters and neutron radiation weighting factor. Results: The preliminary results showed that proton therapy generated much lower risks of second cancer and cardiac toxicities compared to conventional photon therapy, regardless of the changes of potential uncertainties in plausible ranges. Conclusions: The findings of this study suggest that proton therapy will confer lower risks of second cancer and cardiac toxicity compared to conventional photon therapy for children receiving CSI. Sensitivity tests strengthened our conclusion. This study is the prototype of an evidence‐based approach for selecting best treatment modality for pediatric patients. © 2011, American Association of Physicists in Medicine. All rights reserved.

Publication Source (Journal or Book title)

Medical Physics

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