RESUMO
Objective To study how to design the treatment plan to reduce the influence of respiratory movement and the dose of heart and lung as few as possible,to improve the dosage distribution in the target area after radical mastectomy of breast cancer.Methods Twelve patients with breast cancer after radical mastectomy were selected.A dose of 50 Gy with 2 Gy every day and 5 times per week was prescribed.Based on the treatment planning system (TPS),4-field intensity modulated radiotherapy (4FIMRT) and hybrid intensity modulated treatment planning 2-field conformal radiotherapy (2FCRT) + 4FIMRT were designed respectively.The two plans were compared from the aspects of target conformity index (CI),the homogeneity index (HI) and exposure dose volume delivered to organ at risk.Results According to the hybrid plan of 2FCRT + 4FIMRT,HI was 1.08±0.01,which was superior to that from 4FIMRT (1.11±0.01,t =9.587,P ＜ 0.05).While CI was 0.74±0.08,based on the plan of 2FCRT+4FIMRT,which was slightly lower than that from 4FIMRT (0.80±0.03,t =2.497,P ＜ 0.05).Considering the dose volumes on ipsilateral lung in two plans,the values of V5,V10,Dmean of 2FCRT+4FIMRT plan were significantly less than those of 4FIMRT plan.V5,V10,Dmean from the former plan were 13 ％,23 ％,7 ％ less than those from the latter plan (t =6.002,P ＜ 0.05;t =6.826,P ＜ 0.05;t =3.645,P ＜ 0.05).Meanwhile,Dmean of contralateral lung,Dmean of heart,Dmean and V5 of contralateral breast from the 2FCRT +4FIMRT plan were all lower than those of 4FIMRT plan.Those differences between two plans were statistically significant (P ＜ 0.05).Differences of V20 and V30 of ipsilateral lung,and V30 of heart between two plans did not make sense by the statistics analysis (P ＞ 0.05).Conclusion Hybrid radiotherapy theoretically reduces the influence of respiratory movement,improves the uniformity of target dose and lowers the risk of complications of radiation therapy on breast cancer.
