左侧乳腺癌保乳术后全乳腺有无均整器模式下容积旋转调强放疗计划的剂量学比较

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

目的比较左侧乳腺癌保乳术后全乳腺有均整器(FF)与无均整器(FFF)模式下容积旋转调强放疗(VMAT)计划的剂量学差异。方法采用随机数字表法选择2017年8月至2018年8月在徐州市中心医院行左侧乳腺癌保乳术的20例患者,获取定位CT检查资料。FF-VMAT计划与FFF-VMAT计划均采用美国Varian公司ECLIPSE 10.0.4治疗计划系统(TPS)设计。计划靶区(PTV)的处方剂量为50 Gy(2.0 Gy/次),局部瘤床电子线补量照射10 Gy/5次。比较两种计划的剂量学参数差异。结果所有患者两种计划均达到处方剂量要求。与FF-VMAT计划相比,FFF-VMAT计划的适形度(适形指数:0.87±0.04比0.77±0.05)及均匀度(均匀指数:7.36±0.88比10.89±3.00)均较好(均P<0.01);FFF-VMAT计划心脏的平均剂量[(7.73±1.44)Gy比(9.16±4.24)Gy]及对侧肺的平均剂量[(3.61±0.74)Gy比(8.42±0.45)Gy]均低(均P<0.01),对侧乳腺的平均剂量[(3.92±1.08)Gy比(2.02±1.42)Gy]高(P<0.01),心脏V_(2 Gy)[(79.27±1.18)%比(58.94±21.25)%]和同侧肺V_(5 Gy)[(44.89±2.17)%比(37.86±8.33)%]均高(均P<0.01)。FF-VMAT计划的机器跳数为(973±89)MU,低于FFF-VMAT计划的(1356±201)MU(P<0.01)。结论FFF-VMAT计划可以有效降低左侧乳腺癌保乳术后放疗的心脏剂量,但是以轻度增加危及器官低剂量区为代价。

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[(1356±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.