Dosimetric Comparison Between Helical Tomotherapy and Volumetric Modulated Arc Therapy for Patients with Synchronous Bilateral Breast Cancer After Breast-Conserving Surgery
[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％,Dmean,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 Dmean 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 V5 Gy,Dmean,and Dmax 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 V20 Gy of both lungs in TOMO plan was higher than that in VMAT plan(P=0.048).The Dmean 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.
breast neoplasmssimultaneous bilateralhelical tomotherapyvolumetric modulated arc therapydosimetric comparition
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