同发双侧乳腺癌保乳术后患者螺旋断层调强放疗与容积弧形调强放疗的剂量学对比分析

Dosimetric Comparison Between Helical Tomotherapy and Volumetric Modulated Arc Therapy for Patients with Synchronous Bilateral Breast Cancer After Breast-Conserving Surgery

[目的]比较同发双侧乳腺癌保乳术后患者采用螺旋断层调强放疗(helical tomotherapy,TOMO)技术相较于容积弧形调强放射治疗(volumetric modulated arc therapy,VMAT)技术的剂量学差异。[方法]选取既往采用VMAT治疗的同发双侧乳腺癌保乳术后患者10例,重新进行TOMO计划设计,分别评价靶区的D_(2%)、D_(98%)、平均剂量D_(mean)以及均匀性指数(homogeneity index,HI)、适形度指数(comformal index,CI)和梯度指数(gradient index,GI),危及器官包括心脏、左冠状动脉前降支、双肺、左肺、右肺、食管、肝脏等,并统计机器跳数、出束时间。[结果]TOMO计划的靶区D_(mean)相对较低且高剂量D_(2%)低于VMAT计划(P=0.004、0.002),低剂量D_(98%)两组相当(P=0.444)。在靶区的CI和GI方面,TOMO计划更具优势(P均<0.001),两组HI差异无统计学意义(P=0.120)。TOMO计划的心脏V_(5 Gy)、D_(mean)和左冠状动脉前降支的D_(max)高于VMAT计划,差异均有统计学意义(P<0.001,P=0.007,P=0.031);TOMO计划双肺V_(20 Gy)高于VMAT计划(P=0.048);TOMO计划的肝脏D_(mean)高于VMAT计划(P<0.001)。与VMAT相比,TOMO计划机器跳数增加明显且计划执行时间增加约4.5倍。[结论]在同发双侧乳腺癌中,TOMO与VMAT相比在靶区包绕适形性和剂量跌落上优于常规VMAT技术,除食管外未发现危及器官剂量学优势,计划执行效率上有待提高。

[Objective]To compare the dosimetry difference between helical tomotherapy(TOMO)and volu-metric modulated arc therapy(VMAT)plan in patients with synchronous bilateral breast cancer(SBBC)after breast-conserving surgery.[Methods]Ten patients with SBBC who underwent VMAT after breast-conserving surgery were enrolled in the study.The TOMO plan was re-designed;and D98%,D_(mean),conformation index(CI),homogeneity index(HI)and gradient index(GI)of the target area were evaluated.The receiving capacity of the organs at risk including heart,left anterior descending coronary artery,both lungs,left lung,right lung,esophagus and liver were calculated,and monitor units(MU)and beam-on time(BOT)were counted.[Results]The D_(mean) of the target area of TOMO plan and the high-dose D2%were lower than those of VMAT plan(P=0.004,0.002),while the low-dose D98%was not significantly different between two groups(P=0.444).In terms of CI and GI,TOMO was significantly more advantageous(all P<0.001),and there is no significant difference in HI between the two groups(P=0.120).The V_(5 Gy),D_(mean),and D_(max) of the heart and left anterior descending coronary artery in TOMO plan were significantly higher than those in VMAT plan(P<0.001,P=0.007 and P=0.031).The V_(20 Gy) of both lungs in TOMO plan was higher than that in VMAT plan(P=0.048).The D_(mean) of liver in TOMO plan was higher than that of VMAT plan(P<0.001).Compared with VMAT,MU of TOMO plan in-creased significantly and the BOT increases about 4.5 times.[Conclusion]For SBBC patients,TOMO is supe-rior to VMAT in terms of target conformation and dose fall off.No dosimetric advantage of the organs at risk was found except in the esophagus,and the efficiency of the plan execution needs to be improved.