Zhang R, Howell R, Giebeler A, Taddei P, Mahajan A, Newhauser W
Mary Bird Perkins Cancer Center, BATON ROUGE, LA.
Louisiana State University, Baton Rouge, LA.
Med Phys. 2012 Jun;39(6Part13):3762-3962. doi: 10.1118/1.4735324.
To compare proton and photon therapies in terms of the risks of second cancers for a pediatric medulloblastoma patient receiving craniospinal irradiation (CSI).
Two CSI treatment plans with 23.4 Gy or Gy (RBE) prescribed dose were computed for a 4-year-old boy withmedulloblastoma: a three-field 6-MV photon therapy plan and a four-field proton therapy plan. The primary doses for both plans were determined using a commercial treatment planning system. Stray radiation doses for proton therapy were determined from Monte Carlo simulations, and stray radiation doses for photon therapy were determined from measured data. The dose-risk model based on Biological Effects of Ionization Radiation VII report was used to estimate risk of second cancer.
Baseline predictions of the relative risk of each organ were always less for proton CSI than for photon CSI after various follow-up years for the patient. The lifetime risks of the incidence of second cancer after proton CSI and photon CSI were 7.7% and 92%, respectively, and the ratio of lifetime risk was 0.083. Uncertainty analysis revealed the qualitative findings of this study were insensitive to any plausible changes of dose-risk models and mean neutron radiation weighting factor.
Proton therapy confers lower predicted risk of second cancer for the pediatric medulloblastoma patient compared with photon therapy.
比较质子疗法和光子疗法对接受颅脊髓照射（CSI）的小儿髓母细胞瘤患者发生二次癌症的风险。
为一名4岁髓母细胞瘤男孩计算了两个规定剂量为23.4 Gy或Gy（相对生物效应）的CSI治疗计划：一个三野6兆伏光子治疗计划和一个四野质子治疗计划。两个计划的主要剂量均使用商业治疗计划系统确定。质子疗法的杂散辐射剂量通过蒙特卡罗模拟确定，光子疗法的杂散辐射剂量通过测量数据确定。基于《电离辐射的生物学效应VII报告》的剂量风险模型用于估计二次癌症的风险。
在对该患者进行不同随访年份后，质子CSI对各器官相对风险的基线预测始终低于光子CSI。质子CSI和光子CSI后二次癌症发生的终生风险分别为7.7%和92%，终生风险比为0.083。不确定性分析表明，本研究的定性结果对剂量风险模型和平均中子辐射权重因子的任何合理变化均不敏感。
与光子疗法相比，质子疗法对小儿髓母细胞瘤患者二次癌症的预测风险更低。
