Dosimetric comparison of helical tomotherapy and volumetric modulated arc therapy for bilateral breast cancer after breast-conserving surgery
Objective To study the dosimetric difference between helical tomotherapy(HT)and volumetric modulated arc therapy(VMAT)in planning target volume(PTV)and organ at risk(OAR)for bilateral breast cancer after breast-conserving surgery.Methods From June 2018 to June 2022,a total of 15 female patients with bilateral early primary breast cancer who underwent radiotherapy after breast-conserving surgery were enrolled,which aged 34-65 years old with median age of 52 years old;pathological stage was T1N0M0.The HT plan system(Accuray Company)and Monaco planning system(Elekta Company)were used to design HT and VMAT plans for the same patient,respectively.The prescribed dose of two kinds of treatment for bilateral breast cancer was 50 Gy/25f in double target area.The differences in dosemetry parameters of PTV and OAR between HT and VMAT plans were statistically analyzed.Results For PTV,the target doses of the two plans met the clinical requirements.The coverage(D95％)of HT plan was higher than that of VMAT plan.The homogeneity index(HI)of HT decreased from 0.113 to 0.068(P＜0.001),and Dmax of HT was significantly lower than that of VMAT plan[(54.14±0.70)Gy vs(56.27±0.81)Gy.P＜0.001].There was no significant difference in conformity index(CI)between 2 plans(P＞0.05).For OAR,the spinal cordD and whole lungs V5 and heart V5 of HT plan were significantly lower than those of VMAT plan[(3.44±0.42)Gy vs(5.62±0.34)Gy,(39.65±4.40)％vs(52.73±2.50)％,(15.88±2.09)％vs(40.28±1.47)％.P＜0.05],but V20 and V30 of lungs,heart and liver as well as Dmean of liver in HT plan were significantly higher than those of VMAT plan(P＜0.05),there was no significant difference in whole lungs Dmean and heart Dmean between 2 plans(P＞0.05).The treatment time of VMAT was slightly longer than that of HT plan[(886.67±38.09)seconds vs(843.67±21.61)seconds.P=0.013].Conclusion It is demonstrated that HT and VMAT plan could meet the clinical requirements.The HT dosimetric parameter of PTV is superior to that of VMAT,which showes better protection of spinal cord and significantly reduce the low-dose area volume of lung and heart.However,the irradiated volume of HT in moderate-and high-dose areas of lung,heart and liver is significantly higher than that of VMAT,and HT treatment efficiency is slightly higher.
breast-conserving surgery for bilateral breast cancerhelical tomotherapyvolumetric modulated arc therapydosimetric comparison
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