快速旋转调强与五野动态调强在乳腺癌保乳术后放疗中的剂量学比较

A dosimetric comparison of volumetric modulated Arc therapy with conventional intensity- modulated radiotherapy for breast cancer radiotherapy after breast-conserving surgery

目的比较乳腺癌保乳术后RapidArc计划与五野动态调强（5F-IMRT）计划的剂量学差异。方法选择8例左侧乳腺癌保乳术后女性患者，处方剂量为50Gy／25次。分别设计RapidArc计划与5F-IMRT计划。比较两种计划的靶区适形度指数、均匀性指数、靶区覆盖度和危及器官的受照剂量体积，同时比较两组计划实施时的治疗时间和机器跳数。结果在两种计划的靶区比较中，RapidArc计划的靶区适形度指数为（0．88±0．03），高于5F-IMRT计划的（0．79±0．02）（t=8．28，P〈0．05）；RapidArc计划的均匀性指数为（9．01±0．73），优于5F-IMRT计划的（10．44±1．08）（t=-2．73，P〈0．05）。两组计划在同侧肺受照剂量体积比较中RapidArc计划的Dmean、V10、V20、V30小于5F-IMRT计划（t=-7．53、-7．20、-8．39、-7．80，P〈0．05），但RapidArc计划中的也皎5F．IMRT计划增加了约16％（t=5．67，P〈0．05）；心脏的受照剂量体积比较中RapidArc计划中I的Dmean、V5、V10均高于5F-IMRT（t=10．46、28．76、5．40，P〈0．05），但在RapidArc计划中心脏的V30低于5F-IMRT（t=-6．12，P〈0．05）。对侧肺和对侧乳腺的V5在RapidArc计划中明显高于5F-IMRT计划（肺：t=21．50，P〈0．05；乳腺：t=5．44，P〈0．05）。RapidArc计划中机器跳数减少了25％，平均治疗时间节省了60％。结论乳腺癌保乳术后RapidArc计划与5F-IMRT计划比较提高了靶区的适形度和均匀度，减少了高剂量区的受照体积，降低了机器跳数，缩短了治疗时间，但增加7了正常组织低剂量区的受照体积。

Objective To compare the dosimetric differences between two plans of RapidArc and 5F-IMRT for breast cancer radiotherapy after breast-conserving surgery. Methods Eight female patients with left-sided breast cancer after breast-conserving surgery were selected. A dose of 50 Gy in 25 fractions was prescribed for plans of RapidArc and 5F-IMRT. Target.conformity index （CI） , homogeneity index （HI）, target coverage, exposure dose volume delivered to organ at risk were compared between two plans. At the same time, treatment delivery time and monitor units （MU） were also compared. Results The target conformity index （CI） in RapidArc plan （0. 88 ± 0.03） was higher than that in 5F-IMRT plan （0.79±0.02, t =8.28,P〈0.05）. The homogeneity index （HI） in RapidArc plan 9.01 ±0.73 was significantly lower than that in 5F-IMRT planlO. 44 ± 1.08 （t = - 2. 73, P 〈 0. 05）. For the dose volume delivered to the ipsilateral lung in two plans, the values of V^0, V20, V30, and D in RapidArc plan were lower than those in 5F-IMRT plan（t = - 7.53, - 7.20, - 8. 39, - 7.80,P 〈 0.05）. However, the value of Vs in RapidArc plan was higher than that in 5F-IMRT plan （ t = 5.67 ,P 〈 0. 05 ）. For the heart, the values of V5 , V10 and D in RapidArc plan were higher than those in IMRT plan（ t = 10.46,28.76,5.40, P 〈0.05）, while the value of 1/30 in RapidArc plan was lower than that in 5F-IMRT plan（t = -6.12,P 〈 00. 05）. The values of V5 in contralateral lung and breast were higher in RapidArc plan than those in 5F- IMRTplan（lung：t =21.50,P 〈0.05;breast：t =5.44,P 〈0.05）. The MU in Rap＇idArc plan wasdecreased by 25% , and the average treatment delivery time was saved by 60% , compared with that of 5F- IMRT plan. Conclusions During breast cancer radiotherapy after breast-conserving surgery, compared with 5F-IMRT plan, the RapidArc plan could improve the target HI, and reduce both the irradiated dose in high-dose volume and MU, and shorten the treatment time, but increased the exposed volume in low-dose volume of normal tissues.