SU‐E‐T‐276: Equivalent Dose in Children Receiving Craniospinal Irradiation with Photons in a Developing Country Or with Protons in a Developed Country

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Conference Proceeding

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Purpose: Childhood cancer survivors who were treated with craniospinal irradiation (CSI) have a high risk of radiogenic late effects, for example second malignant neoplasms (SMNs). These effects can occur inside or outside of the therapeutic fields. Proton therapy, which is unavailable in developing countries, may offer the possibility to reduce the radiation dose in normal tissues and thereby reducing the risk of late effects. We quantified the equivalent dose in organs at risk for SMNs for 9 children ages 2 to 14 years who received proton CSI in a developed country and the doses they would have received from photon CSI in a developing country. Methods: For each child, 23.4‐Gy treatment plans were created according the standards of care of leading cancer centers in a developed country (proton CSI) and in a developing country (photon CSI). For each patient and clinic, equivalent dose was determined throughout the patients' bodies. In‐field dose was calculated using treatment planning systems of our clinics. Out‐of‐field dose was calculated using Monte Carlo simulations for proton CSI and applying a measurement‐based model for photon CSI. Mean equivalent dose was determined in organs at risk of SMNs‐‐red bone marrow, bladder, breasts, liver, lungs, ovaries, prostate, stomach, uterus, colon, skin, and remainder tissues. Results: Mean organ equivalent doses averaged over 9 all patients were less in proton CSI than in photon CSI in all organs and tissues except skin. We observed minor (<30%) reductions in equivalent dose in the lungs, red bone marrow, and remainder tissues and larger (>85%) reductions in all other organs. Conclusion: Equivalent dose was reduced for children receiving CSI with proton beams rather than photon beams. It may be possible to reduce the risk of radiogenic SMNs for children in developing countries needing CSI if proton therapy is made available to them. Fogarty International Center, National Institutes of Health, K01‐TW008409; National Cancer Institute, National Institutes of Health, R01‐CA131463‐01A1; Northern Illinois University through a subcontract of Department of Defense W81XWH‐08‐1‐0205; We do not have any conflicts of interest. © 2013, American Association of Physicists in Medicine. All rights reserved.

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Medical Physics

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