保乳术后逆向、正向IMRT和3DCRT计划下内乳区非计划性受量比较研究

Comparison of incidental irradiation dose to the internal mammary nodes among I-IMRT, F-IMRT, and 3DCRT after breast-conserving surgery

目的探讨保乳术后逆向调强（I-IMRT）、正向调强（F-IMRT）和三维适形（3DCRT）计划间内乳区非计划性受照剂量的差异，为临床判断能否将内乳区免于放疗提供依据。 方法选取84例保乳术后乳腺癌患者，勾画前3肋间内乳区，为每例患者设计3种放疗计划，内乳区不包括在计划靶区内，Wilcoxon符号秩和检验比较3种计划间的差异。结果前3肋间I-IMRT、F-IMRT、3DCRT计划间内乳区Dmean均无差异，中位数分别为2740.2、2973.9、2951.4 cGy。3个肋间单独分析，3种计划第1肋间和第2肋间的Dmean相近，第3肋间I-IMRT的Dmean明显高于3DCRT和F-IMRT。3种计划单独分析，每种计划第3肋间的Dmean均最高，其次为第2肋间，第1肋间最低。结论3种计划均不能达到治疗亚临床病灶的处方剂量，且3种计划间无明显差异。因此，对于临床上有指征照射内乳的患者来说，应用该3种放疗技术中的任何一种，将内乳靶区排除在外是不保险的。然而，随着化疗、内分泌及靶向等治疗方式的综合应用，内乳区非计划性受照剂量能否达到临床要求尚需进一步的随访。

ObjectiveTo explore the dosimetric variance in incidental irradiation to the internal mammary nodes among inverse intensity-modulated radiotherapy （I-IMRT）, forward intensity-modulated radiotherapy （F-IMRT）, and three-dimensional conformal radiotherapy （3DCRT） after breast-conserving surgery, and to provide a basis for deciding whether to spare the internal mammary nodes in clinical treatment. Methods A total of 84 patients undergoing breast-conserving surgery were enrolled as subjects. The internal mammary nodes in the first three intercostal spaces were contoured. Three radiotherapy plans were designed for each patient. The internal mammary nodes were not included in the planning target volume. Comparison was made among the three plans. The results were compared using Wilcoxon signed rank test. Results The I-IMRT, F-IMRT, and 3DCRT plans had similar median Dmean values for the internal mammary nodes, which were 2740.2, 2973.9, and 2951.4 cGy, respectively. The analyses of the three individual intercostal spaces showed that there was no difference in Dmean for the first intercostal space or the second intercostal space between the three plans; For the third intercostal space, however, I-IMRT had a significantly higher Dmean than 3DCRT and F-IMRT. The analyses of the three individual plans showed that for each plan, the Dmean was the highest in the third intercostal space, followed by the second intercostal space and the first intercostal space. Conclusions All the three plans fail to attain an adequate prescribed dose to cure subclinical disease, and there is no significant difference among the three plans. Therefore, it is risky to exclude the internal mammary nodes using any one of the three radiotherapy techniques for patients with clinical indications for internal mammary nodes radiation. In the combination therapy including chemotherapy, endocrine therapy, and targeted therapy, however, further follow-up is needed to determine whether the incidental irradiation dose to the internal mammary nodes could meet clinical requirement.