Radiation Medicine Research Center, Department of Radiation Oncology, Rigshospitalet, University of Copenhagen, Denmark.
Acta Oncol. 2011 Aug;50(6):806-16. doi: 10.3109/0284186X.2011.582514.
The aim of this model study was to estimate and compare the risk of radiation-induced adverse late effects in pediatric patients with medulloblastoma (MB) treated with either three-dimensional conformal radiotherapy (3D CRT), inversely-optimized arc therapy (RapidArc(®) (RA)) or spot-scanned intensity-modulated proton therapy (IMPT). The aim was also to find dose-volume toxicity parameters relevant to children undergoing RT to be used in the inverse planning of RA and IMPT, and to use in the risk estimations.
Treatment plans were created for all three techniques on 10 pediatric patients that have been treated with craniospinal irradiation (CSI) at our institution in 2007-2009. Plans were generated for two prescription CSI doses, 23.4 Gy and 36 Gy. Risk estimates were based on childhood cancer survivor data when available and secondary cancer (SC) risks were estimated as a function of age at exposure and attained age according to the organ-equivalent dose (OED) concept.
Estimates of SC risk was higher for the RA plans and differentiable from the estimates for 3D CRT at attained ages above 40 years. The risk of developing heart failure, hearing loss, hypothyroidism and xerostomia was highest for the 3D CRT plans. The risks of all adverse effects were estimated as lowest for the IMPT plans, even when including secondary neutron (SN) irradiation with high values of the neutron radiation weighting factors (WR(neutron)).
When comparing RA and 3D CRT treatment for pediatric MB it is a matter of comparing higher SC risk against higher risks of non-cancer adverse events. Considering time until onset of the different complications is necessary to fully assess patient benefit in such a comparison. The IMPT plans, including SN dose contribution, compared favorably to the photon techniques in terms of all radiobiological risk estimates.
本模型研究的目的是评估和比较接受三维适形放疗（3D CRT）、逆向优化弧形治疗（RapidArc(®)（RA））或点扫描强度调制质子治疗（IMPT）治疗的髓母细胞瘤（MB）儿科患者的放射性不良迟发性效应风险。该研究还旨在找到与接受 RT 治疗的儿童相关的剂量-体积毒性参数，以便在 RA 和 IMPT 的逆规划中使用，并用于风险估计。
对 2007-2009 年在我院接受颅脊髓照射（CSI）治疗的 10 名儿科患者分别进行了三种技术的治疗计划。为两种处方 CSI 剂量（23.4 Gy 和 36 Gy）生成了计划。风险估计基于儿童癌症幸存者的数据，如有可用数据，并根据器官等效剂量（OED）概念，将二次癌症（SC）风险估计为暴露年龄和获得年龄的函数。
RA 计划的 SC 风险估计值高于 3D CRT 计划，在获得年龄超过 40 岁时，两者之间存在可区分的差异。3D CRT 计划发生心力衰竭、听力损失、甲状腺功能减退和口干的风险最高。即使包括具有较高中子辐射权重因子（WR(neutron)）的二次中子（SN）照射，IMPT 计划的所有不良影响风险估计值也最低。
在比较 RA 和 3D CRT 治疗儿科 MB 时，关键在于比较高的 SC 风险与更高的非癌症不良事件风险。在这种比较中，考虑不同并发症的发病时间对于全面评估患者获益是必要的。包括 SN 剂量贡献的 IMPT 计划在所有放射生物学风险估计方面均优于光子技术。
