ABSTRACT
Objective To explore the optimal radiotherapy method by comparing the dosimetric differences of target and organs at risk of four radiotherapy plans for left sided breast cancerafter breast-conserving surgery. Methods Twenty-three patients with left breast cancer were randomly selected and given PTV 25 fractions, 50 Gy prescription dose.TheHybrid_IMRT, rj_IMRT, VMAT and t_VMAT plans were designed for each patients. Dosimetric differences were compared, including dose volume histograms of target and OARs, target homogeneity indexes (HI), conformal indexes (CI) and the machine MUs. Results Target Dosimetric comparison, HI: t_VMAT plan target has highest HI and had significant difference (P ≤ 0.001); The target CI of VMAT plans were 0.967 ± 0.016, had significant difference compared with the other 3 plans (P < 0.05). The CI of rj_ IMRT were 0.942 ± 0.018 better than that of IMRT and t_VMATs. Dosimetric comparison of OARs, left_lung mean dose (MLD_L): rj_IMRT were （8.76 ± 1.52） Gy which were best of 4 plans, and had statistical significance (P < 0.05). Heart mean dose: rj_IMRT were （4.68 ± 0.87） Gy were better than that of VMAT (P < 0.05). Conclusion All of these four plans could be applied in clinical treatments, while the limitations of treatment equipment, patients’ physical conditions and some other factors should be considered before selecting an appropriate one.