电子-光子线混合调强与单纯光子线调强在左乳腺癌放疗中的剂量对比研究

Dosimetric comparison of E-X hybrid intensity modulated radiation therapy and X-ray intensity modulated radiation therapy for left breast cancer

目的:比较在左乳腺癌保乳术后调强计划设计时,单纯X线与电子线混合X线两种方案之间的剂量差异,探讨在左乳腺癌保乳术后调强放疗时采用电子-光子线混合照射的可行性。方法:随机选择在放疗中心接受放疗的左乳腺癌病人10例,为每个病例设计两个调强计划,命名为计划X和计划E-X。计划X为单纯的光子线调强计划;计划E+X为电子-光子线混合调强计划。计划X和计划E-X有相同的主射野数和主射野角度,并给定相同的处方剂量50.0 Gy,单次剂量2.0 Gy。在靶区剂量均满足临床要求的前提下,对比靶区适形度、双肺V5、V10和Dmean、心脏V30、V40和Dmean、脊髓Dmax、对侧乳腺Dmax等参数的剂量学差异。结果:PTV的适形度指数CI在两个计划中不存在统计学差异(P=0.511);左右肺的V5、V10、Dmean,心脏的Dmean和脊髓的Dmax在两个计划中均存在明显的统计学差异(P<0.01);心脏的V40和对侧乳腺的Dmax在两个计划中不存在统计学差异(P>0.05)。结论:与单纯的光子线调强比较,电子-光子线混合调强治疗保乳术后的左乳腺癌具有明显的剂量优势。

Objective To discuss on the practicability of E-X hybrid intensity modulated radiation therapy （IMRT） for left breast cancer after conserving surgery by comparing the dosimetric difference between X-ray IMRT plan and E-X hybrid IMRT plan after the left breast conserving surgery. Methods Ten patients who received left breast conserving surgery were randomly selected, each patient of 2 IMRT plans, named as plan X and plan E-X. Plan X was the conventional X-ray IMRT plan and plan E-X was a hybrid IMRT plan which contained both X-ray and electron beams. Same numbers and angles of beams were set for these 2 plans. Same prescription （50.0 Gy） was given, 2.0 Gy for each time. Based on that the prescription of target volume met clinical requirements, the dosimetric differences of conformal indexes （CI） of target volumes, V5, V10, mean dose of both lungs, V30, V40 and mean dose of heart, max dose of spinal cord and max dose of contralateral breast were compared. Results No obvious statistical differences were found in CI of target volumes between these two plans （P=0.511）. There were obvious statistical differences between these two plans in the V5, V10 and mean dose of both lungs, the mean dose of heart, the max dose of spinal cord （P〈0.01）, however, the V40 of heart and the max dose of contralateral breast had no statistical differences between these two plans （P〉0.05）. Conclusion Compared with the X-ray IMRT, E-X hybrid IMRT for left breast cancer after conserving surgery has significant dosimetric advantage.