SU-E-T-258: Assessment of Radiation Induced Second Cancer Risks in Proton Therapy and IMRT for Organs inside the Main Radiation Field

Medical Physics
Harald PaganettiTorunn I Yock

Abstract

Radiation therapy can potentially cause a second malignancy. There is clinical evidence that those occur typically within the beam path in the medium/high dose region. The purpose of this study was to assess the risk for developing a radiation induced tumor within the treated volume and to compare this risk for proton therapy and IMRT. Fully contoured age and gender specific whole body phantoms (4-year and 14-year old) were uploaded into a treatment planning system and typical tumor volumes were contoured based on patients treated for optic glioma and vertebral body Ewing's sarcoma. Lifetime attributable risks (LARs) for developing a second malignancy were calculated using a risk model incorporating factors for cell kill, mutations, repopulation, and inhomogeneous organ doses. For standard fractionation schemes, the LAR for developing a second malignancy from radiation therapy alone were found to be up to 2.7% for a 4-year old optic glioma patient treated with IMRT considering a soft tissue carcinoma risk model only. Sarcoma risks were found to be below 1% in all cases. For the 14-year old, risks were found to be about a factor of 2 lower. For the Ewing's sarcoma cases the risks based on the sarcoma model were typically higher ...Continue Reading

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