Introduction
To compare post-implant dosimetric parameters of computed tomography (CT)-guided radioactive iodine-125 (125I) seed (RIS) implantation assisted with and without three-dimensional printing non-coplanar template (3D-PNCT) in locally recurrent rectal cancer (LRRC).

Material and methods
One hundred and fifty-five LRRC patients treated by CT-guided RIS implantation assisted with or without 3D-PNCT from October 2003 to May 2019 were included in this study. Propensity score matching (PSM) method (1 : 1) was used to adjust for differences between the 3D-group (with 3D-PNCT) and the CT-group (without 3D-PNCT). After PSM, dosimetric parameters [D90 (dose that covered 90% of target volume), D100 (dose that covered 100% of target volume), V100 (percentage of gross tumor volume (GTV) receiving 100% of prescription dose), V150 (percentage of GTV receiving 150% of prescription dose), HI (homogeneity index), CI (conformity index), and EI (external index)] of the two groups were compared.

Results
After PSM, 45 pairs of matched cases were selected for analysis and differences in variables between the two groups were balanced. For the 3D-group, median values of D90, D100, V100, V150, EI, and HI were 142.6 Gy (73.7-218.2 Gy), 73.7 Gy (26.2-169.3 Gy), 94.1% (74.3-100%), 71.8% (35.4-98.3%), 0.7 (0.1-30.7), and 0.20 (0-0.60), respectively, and corresponding values were 119.9 Gy (39.8-159.3 Gy), 47.0 Gy (13.0-200.9 Gy), 89.9% (38.6-100%), 62.8% (14.8-100%), 0.39 (0-11.01), and 0.30 (0-0.95), respectively, for the CT-group. Parameters including D90, D100, V100, V150, and EI in the 3D-group were significantly higher than those in the CT-group (p < 0.001, p < 0.001, p < 0.001, p < 0.001, and p = 0.006, respectively).

Conclusions
3D-PNCT can improve the accuracy of radioactive seed implantation by increasing the dose delivered to the tumor and reducing the number of “cold” spots of dose.



中文翻译：

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计算机断层扫描引导的碘125种子植入辅助和不辅助三维印刷非共面模板在局部复发性直肠癌中的剂量学比较：倾向评分匹配研究

简介
比较局部X线摄影术（CT）引导的放射性碘125（125I）种子（RIS）植入与有无三维印刷非共面模板（3D-PNCT）在局部复发性直肠癌中的植入后剂量参数（LRRC）。

材料与方法
2003年10月至2019年5月，155例接受CT引导下的RIS植入治疗的LRRC患者在有无3D-PNCT的情况下进行了辅助治疗。倾向得分匹配（PSM）方法（1：1）用于调整3D组（使用3D-PNCT）和CT组（不使用3D-PNCT）之间的差异。在PSM之后，剂量参数[D90（覆盖目标体积的90％的剂量），D100（覆盖目标体积的100％的剂量），V100（接受处方剂量的100％的肿瘤总体积（GTV）的百分比），V150（比较两组的150％处方剂量的GTV百分比），HI（均一性指数），CI（合格指数）和EI（外部指数）。

结果
在PSM之后，选择45对匹配的病例进行分析，并平衡两组之间变量的差异。对于3D组，D90，D100，V100，V150，EI和HI的中位数分别为142.6 Gy（73.7-218.2 Gy），73.7 Gy（26.2-169.3 Gy），94.1％（74.3-100％），71.8百分比（35.4-98.3％），0.7（0.1-30.7）和0.20（0-0.60），相应的值为119.9 Gy（39.8-159.3 Gy），47.0 Gy（13.0-200.9 Gy），89.9％（ CT组分别为38.6-100％，62.8％（14.8-100％），0.39（0-11.01）和0.30（0-0.95）。3D组中的参数D90，D100，V100，V150和EI显着高于CT组（p <0.001，p <0.001，p <0.001，p <0.001和p = 0.006 ）。

结论
3D-PNCT可通过增加传递给肿瘤的剂量并减少“冷”剂量点的数量来提高放射性种子植入的准确性。