Dosimetric comparison of volumetric modulated arc therapy plans with flattening filter and flattening filter-free for whole-breast radiation therapy after breast conserving surgery for left breast cancer / 肿瘤研究与临床

ABSTRACT

Objective:To compare the dosimetric difference between volumetric modulated arc therapy (VMAT) plans with flattening filter (FF) and flattening filter-free (FFF) for whole-breast radiation therapy after breast conserving surgery for left breast cancer.Methods:Twenty patients with left breast cancer who underwent breast conserving surgery in Xuzhou Central Hospital from August 2017 to August 2018 were selected by random number table method, and the CT data were obtained. Both FF-VMAT plan and FFF-VMAT plan were designed with ECLIPSE 10.0.4 treatment planning system (TPS) of American Varian company. The prescription dose of the planned target volume (PTV) was 50 Gy (2 Gy/time), and the local tumor bed was irradiated with 10 Gy/5 times. The dosimetric parameters of the two plans were compared.Results:The two plans of all patients met the prescription dose requirements. Compared with FF-VMAT plan, FFF-VMAT plan had better conformity (conformal index 0.87±0.04 vs. 0.77±0.05) and homogeneity (homogeneity index 7.36±0.88 vs. 10.89±3.00) (both P < 0.01); FFF-VMAT plan had lower average dose of heart [(7.73±1.44) Gy vs. (9.16±4.24) Gy] and contralateral lung [(3.61±0.74) Gy vs. (8.42±0.45) Gy] (both P < 0.01), FFF-VMAT plan had higher average dose of contralateral breast [(3.92±1.08) Gy vs. (2.02±1.42) Gy] ( P < 0.01), and V 2 Gy in the heart [(79.27±1.18)% vs. (58.94±21.25)%] and V 5 Gy in the ipsilateral lung [(44.89±2.17)% vs.(37.86±8.33)%] (all P < 0.01). The monitor unit of the FF-VMAT plan was (973±89) MU, which was lower than that of the FFF-VMAT plan [(1 356±201) MU] ( P < 0.01). Conclusion:FFF-VMAT plan can effectively reduce the cardiac dose after breast conserving surgery for left breast cancer, but it increases the risk of organ damage at low dose area.