Lideståhl Anders, Johansson Gracinda, Siegbahn Albert, Lind Pehr A
Department of Oncology-Pathology, Karolinska Institutet, 17177 Stockholm, Sweden.
Department of Oncology, Södersjukhuset, 11883 Stockholm, Sweden.
Cancers (Basel). 2021 Oct 14;13(20):5153. doi: 10.3390/cancers13205153.
We compared the calculated risks of radiation-induced secondary malignant neoplasms (SMNs) for patients treated for thymic tumors with 3D-CRT, IMRT, or single-field uniform dose (SFUD) proton beam therapy (PBT) using the pencil beam scanning (PBS) technique. A cancer-induction model based on the organ equivalent dose (OED) concept was used. For twelve patients, treated with 3D-CRT for thymic tumors, alternative IMRT and SFUD plans were retrospectively prepared. The resulting DVHs for organs at risk (OARs) were extracted and used to estimate the risk of SMNs. The OED was calculated using a mechanistic model for carcinoma induction. Two limit cases were considered; the linear-exponential model, in which the repopulation/repair of the cells is neglected, and the plateau model, in which full repopulation/repair of the irradiated cells is assumed. The calculated risks for SMNs for the different radiation modalities and dose-relation models were used to calculate relative risks, which were compared pairwise. The risks for developing SMNs were reduced for all OARs, and for both dose-relation models, if SFUD was used, compared to 3D-CRT and IMRT. In conclusion, PBS shows a potential benefit to reduce the risk of SMNs compared to 3D-CRT and IMRT in the treatment of thymic tumors.
我们使用笔形束扫描（PBS）技术，比较了接受三维适形放疗（3D-CRT）、调强放疗（IMRT）或单野均匀剂量（SFUD）质子束治疗（PBT）的胸腺肿瘤患者辐射诱发继发性恶性肿瘤（SMN）的计算风险。采用了基于器官等效剂量（OED）概念的癌症诱发模型。对于12例接受3D-CRT治疗胸腺肿瘤的患者，回顾性制定了替代的IMRT和SFUD计划。提取由此产生的危及器官（OAR）的剂量体积直方图（DVH），并用于估计SMN的风险。使用癌症诱发的机制模型计算OED。考虑了两种极限情况；线性指数模型，其中忽略细胞的再增殖/修复；以及平台模型，其中假定受照射细胞完全再增殖/修复。使用不同放疗方式和剂量关系模型计算的SMN风险用于计算相对风险，并进行两两比较。与3D-CRT和IMRT相比，如果使用SFUD，所有OAR以及两种剂量关系模型发生SMN的风险均降低。总之，在胸腺肿瘤治疗中，与3D-CRT和IMRT相比，PBS显示出降低SMN风险的潜在益处。
