Chongqing University Cancer Hospital, Chongqing, China.
Chongqing Key Laboratory of Translational Research for Cancer Metastasis and Individualized Treatment, Chongqing University Cancer Hospital & Chongqing Cancer Institute & Chongqing Cancer Hospital, Chongqing, China.
Technol Cancer Res Treat. 2019 Jan-Dec;18:1533033819886899. doi: 10.1177/1533033819886899.
To quantify the risk of radiogenic second cancer in pediatric patients receiving hippocampal-sparing craniospinal irradiation either with intensity-modulated radiation therapy or tomotherapy due to the development of a solid second cancer after radiotherapy using the concept of excess absolute risk.
Computed tomography images of 15 pediatric patients who received craniospinal irradiation treatment were selected for this study. For each case, intensity-modulated radiation therapy and tomotherapy plans were computed. Then, the dosimetry parameters were analyzed. Differential dose-volume histograms were generated, and the excess absolute risks were calculated for each plan of each patient.
The tomotherapy group was superior to the intensity-modulated radiation therapy group in target area homogeneity index ( < .001). Tomotherapy offered greater hippocampal sparing than intensity-modulated radiation therapy in terms of (15.66 vs 23.05 Gy, < .001) and D (9.79 vs 20.29 Gy, < .001). Tomotherapy craniospinal irradiation induced a much higher risk than intensity-modulated radiation therapy craniospinal irradiation to the thyroid and lungs (excess absolute risk: thyroid 28.7 vs 26.9 per 10 000 PY, = .010; lung 20.5 vs 18.9 per 10 000 PY, = .003). Both techniques conferred a higher risk to the stomach, but there was little difference. In addition, the 2 plans induced less carcinogenic risk to the liver (excess absolute risk 4.2 vs 4.0 per 10 000 PY, = .020).
The tomotherapy plan has obvious advantages in the protection of the hippocampus for children undergoing craniospinal irradiation treatment. Tomotherapy increased the risk of radiogenic second cancer in organ at risk, and therefore, it is imperative to take the risk factor into consideration in the formulation of treatment protocols.
利用超额绝对风险的概念，量化因放疗后发生实体第二癌而接受调强放疗或托姆刀行海马保护颅脊髓照射的儿童患者发生放射性第二癌的风险。
选择 15 例接受颅脊髓照射治疗的儿童患者的 CT 图像进行本研究。对于每个病例，计算了调强放疗和托姆刀治疗计划。然后，分析了剂量学参数。生成了差分剂量-体积直方图，并计算了每位患者每个计划的超额绝对风险。
在靶区均匀性指数方面，托姆刀组优于调强放疗组（<0.001）。在海马保护方面，托姆刀优于调强放疗，（15.66 对 23.05 Gy，<0.001）和 D（9.79 对 20.29 Gy，<0.001）。颅脊髓照射的托姆刀治疗比调强放疗诱导甲状腺和肺部发生更高的风险（超额绝对风险：甲状腺 28.7 对 26.9 每 10 000 人年，=0.010；肺 20.5 对 18.9 每 10 000 人年，=0.003）。两种技术对胃的风险更高，但差异不大。此外，这两种方案对肝脏的致癌风险较低（超额绝对风险 4.2 对 4.0 每 10 000 人年，=0.020）。
托姆刀治疗计划在保护接受颅脊髓照射治疗的儿童海马方面具有明显优势。托姆刀治疗增加了放射性第二癌在危险器官的风险，因此，在制定治疗方案时必须考虑风险因素。
