基于VMAT的混合调强技术在乳腺癌保乳术后放疗中的应用研究

Application of VMAT-based hybrid intensity-modulated technique on tumor bed boost after Breast-conservative surgery for breast cancer

目的评估3DCRT+VMAT的混合调强技术在乳腺癌保乳术后瘤床同步加量放疗中的剂量学优势及临床实用性。方法选择10例乳腺癌保乳术后患者,在同一优化条件下,分别设计基于VMAT的混合调强计划(3DCRT+VMAT)和基于IMRT的混合调强计划(3DCRT+IMRT),比较两组计划的靶区适形度指数(CI)、均匀性指数(HI)、危及器官的受照剂量体积。结果 3DCRT+VMAT组中PTV的D_(95)为50. 29±0. 25,优于3DCRT+IMRT组的50. 69±0. 20(P<0. 05),两组计划PGTV的D_(95)、PTV和PGTV的CI、HI无统计学差异(P>0. 05); 3DCRT+VMAT组心脏的D_(mean)、V_(30)较3DCRT+IMRT组有所降低,且具有统计学意义(P <0. 05);在3DCRT+VMAT组健侧乳腺的D_(mean)为1. 31±0. 44低于3DCRT+IMRT组的1. 88±0. 28 (P <0. 05),两组计划患侧肺V_5、V_(10)、V_(20)、D_(mean)、健侧肺的D_(mean)无统计学差异(P>0. 05); 3DCRT+VMAT组较3DCRT+IMRT组机器跳数减少了31%(P <0. 05),平均治疗时间节省了38%(P <0. 05)。结论基于VMAT的混合调强方式与基于IMRT的混合调强方式相比,在保证靶区的适形度和均匀性前提下,更好的保护了心脏和健侧乳腺,同时显著缩短了计划执行时间,具有较高的临床应用潜力。

Objective To evaluate dosimetry advantage and clinical application of hybrid intensity-modulated radiotherapy with 3 DCRT/VMAT in radiotherapy with tumor bed boost after breast-conservative surgery. Methods Ten patients with breast cancer after breast-conservative surgery were enrolled. Under the same optimization conditions,the VMAT-based hybrid planning( 3 DCRT+VMAT) and the IMRT-based hybrid planning( 3 DCRT+IMRT) are designed respectively. The conformity index( CI),homogeneity index( HI),volume of exposure dose on organs at risk in patients from two plans were compared. Results According to the hybrid plan of 3 DCRT+VMAT,D95 of Planning Target Volume( PTV) is 50. 29 ± 0. 25,which is superior to that from 3 DCRT+IMRT,50. 69 ± 0. 20(P<0.05). There was neither statistical difference of D95 and PTV between two plans,nor difference of CI and HI of pretreatment gross tumor volume( PGTV). In the comparison with exposure dose volume delivered to the heart in two plans,the values of V30 and Dmean in the plan of 3DCRT +VMAT were lower than the ones in 3DCRT+ IMRT( P<0.05). Dmeanof the contra-lateral breast in the 3 DCRT+VMAT group is 1. 31 ± 0. 44,that is inferior to the group of 3 DCRT+IMRT,which is 1. 88 ± 0. 28(P<0.05). While V5,V10,V20,Dmean of ipsilateral lung dose and Dmean of cardiac and contra-lateral lung dose had no statistical difference( P > 0. 05). The monitor units( MU) of 3 DCRT/VMAT Plan were 31%(P<0.05) less than that of 3 DCRT+IMRT Plan,while the average treatment time of the former plan was 38%( P <0. 05) less than the latter. Conclusion Compared with the IMRT-based hybrid plan,the VMAT-based hybrid plan better protects the heart and the healthy breast while ensuring the conformity and uniformity of the target area,and significantly shortens the schedule execution time. Therefore,it has a high potential for clinical application.