Study the dosimetric for whole breast irradiation with fixed field IMRT and helical tomotherapy

Abstract

Objective To compare the dosimetry difference between helical tomotherapy and fixed field IMRT for breast cancer radiotherapy after breast-conserving surgery.Methods Ten patients received radiotherapy after breast-conserving surgery were selected.For each patient,two treatment plans (FF-IMRT plan and HT plan) were designed with Eclipse and TomoTherapy.Same institutional dose-volume constraints for breast cancer were used in both techniques.Targets and organs at risk were compared with paired t-test for two planning.Results In comparison with the FF-IMRT planning,PTV coverage of HT plan group increased,Dmean became lower (P =0.000,0.002).the HI and CI were significantly higher for HT (P =0.001,0.023).Compared with the FF-IMRT plans,V5,V10,V20,V30,V40 and D of the ipsilateral lung were reduced by about 28％,30％,35％,46％,61％ and 32％ (P =0.000),those of full lung were reduced by about 30％,28％,34％,46％,62％ and 26％ (P =0.000),those and Dmax of heart were reduced by about 57％,59％,71％,82％,91％,45％ and 12％ (P =0.000-0.002).The Dmean and Dmax of contralateral breast were higher by 0.9 Gy and 3.0 Gy (P =0.000,0.000) respectively,those of contralateral lung were higher by 0.42 Gy and 2.70 Gy (P =0.000,0.000) respectively.It takes significantly long time for the HT plans designed than FF-IMRT plan (11.98 min:5.96 min,P =0.000).Conclusions The HT planning improve the HI and CI of PTV,organs at risk can get equivalent or superior dose distribution compared with the FF-IMRT technology,but it is feasible for clinical applications in breastconserving surgery as a new method. Key words: Breast neoplasms/fixed field intensity-modulated radiotherapy; Breast neoplasms/helical tomotherapy ; Dosimetry