Dosimetric Comparison Of Intensity Modulated Radiotherapy Plans With Different Numbers Of Beam For Left Breast Cancer After Breast-conserving Surgery

Objective:to study the appropriate treatment planning for left-sided breast cancer patients by comparing the IMRT plans with different numbers of field. Materials and Methods:20patients with left-side breast carcinoma treated with radiotherapy in our hospital after breast-conserving surgery were randomly selected.4beams,5beams and 6beams IMRT plans were designed for each patient. Each plan had the same dose-volume constraints, the prescription dose was 50GY.This three type of IMRT plan were compared to each other by dose distribution of target, CI and HI of PTV and the irradiated dose of organs at risk (OARs). Results:with the increasing beam number of IMRT plan, CI and HI of target were improved. (CI:IMRT4:0.737; IMRT5:0.769; IMRT6:0.798. HI: IMRT4:1.103; IMRT5:1.088; IMRT6:1.073).6F-IMRT improved V95%andV100% of PTV significantly.6F-IMRT compared to 4F-IMRT and 5F-IMRT, the irradiated dose of cardiac and lung had no significant difference, and the irradiation volume of right breast was reduced by 4F-IMRT, but each type of plan was under the tolerance dose. The MU is 4F-IMRT< 5F-IMRT< 6F-IMRT, there are significant differences among these three plans. Conclusions:6F-IMRT can improve dose distribution of target volume better than 4F-IMRT and 5F-IMRT without increasing irradiated dose of OARs.