左侧乳腺癌保乳术后瘤床同步推量容积调强放疗与断层径照剂量学研究

Dosimetric study of volumetric modulated arc therapy and tomo direct simultaneous integrated boost for patients receiving breast-conserving surgery for left breast cancer

目的探究容积调强放疗(VMAT)和断层径照(TD)在左侧乳癌保乳术后瘤床同步推量放疗中的剂量学差异,为临床提供更多剂量学参考。方法选取云南省肿瘤医院放射治疗科2018年12月至2020年6月收治的22例左侧乳腺癌保乳术后已行同步推量放疗患者的定位CT影像和靶区危及器官等结构资料,针对同一患者分别设计VMAT和TD两种放疗计划,对两种放疗计划靶区和危及器官剂量学差异进行比较分析。结果靶区剂量学方面,VMAT和TD两种放疗计划瘤床计划靶区(PGTV)的D_(2%)分别为(59.99±0.19)Gy、(59.55±0.51)Gy,D_(98%)分别为(57.19±0.08)Gy、(57.46±0.22)Gy,适形指数(CI)分别为0.76±0.05、0.58±0.13,均匀性指数(HI)分别为0.05±0.00、0.04±0.01,差异均有统计学意义(t=4.09,P<0.001;t=-5.10,P<0.001;t=8.19,P<0.001;t=4.89,P<0.001);D_(50%)分别为(58.73±0.10)Gy、(58.73±0.24)Gy,差异无统计学意义(t=-0.03,P=0.974)。两种放疗计划计划靶区(PTV)的D_(50%)分别为(52.21±0.33)Gy、(53.00±0.72)Gy,D_(98%)分别为(48.44±0.43)Gy、(49.09±0.21)Gy,CI分别为0.83±0.06、0.67±0.06,HI分别为0.20±0.01、0.19±0.01,差异均有统计学意义(t=-4.81,P<0.001;t=-6.80,P<0.001;t=10.52,P<0.001;t=8.75,P<0.001);D_(2%)分别为(59.01±0.45)Gy、(59.00±0.48)Gy,差异无统计学意义(t=0.22,P=0.830)。危及器官剂量学方面,VMAT和TD两种放疗计划左肺V20分别为(18.81±2.86)%、(22.03±1.91)%,D_(mean)分别为(11.66±1.32)Gy、(12.85±1.46)Gy;右肺V5分别为(5.70±2.90)%、(0.30±0.13)%,D_(mean)分别为(2.45±0.29)Gy、(0.43±0.14)Gy;右侧乳腺D_(mean)分别为(3.22±0.72)Gy、(1.69±0.80)Gy;脊髓D_(2%)分别为(5.37±1.97)Gy、(0.46±0.09)Gy,差异均有统计学意义(t=-5.36,P<0.001;t=-4.10,P=0.007;t=16.44,P<0.001;t=9.09,P<0.001;t=5.41,P<0.001;t=11.75,P<0.001)。左肺V5分别为(53.00±5.99)%、(50.00±7.69)%,右侧乳腺V5分别为(11.51±4.60)%、(8.06±3.49)%,心脏V30分别为(1.49±0.69)%、(1.51±0.71)%,D_(mean)分别为(3.99±0.97)Gy、(3.90±1.03)Gy,差异均无统计学意义(t=1.91,P=0.061;t=1.59,P=0.120;t=-0.06,P=0.952;t=0.56,P=0.581)。结论左侧乳癌保乳术后同步推量VMAT和TD均能满足临床剂量学要求,但两种技术各有特点,VMAT适形性较优,TD均匀性较优;TD对健侧危及器官右肺、右侧乳腺、脊髓的保护明显优于VMAT;VMAT对患侧左肺的保护较优;对心脏的保护两者无明显差异。

Objective To explore the dosimetry difference between volumetric modulated arc therapy(VMAT)and tomo direct(TD)in tumor bed simultaneous push radiotherapy after left breast-conserving surgery,and to provide more dosimetry reference for clinic.Methods A total of 22 patients with left breast cancer who underwent simultaneous quantitative radiotherapy after breast-conserving surgery were selected from the Department of Radiation Oncology,Yunnan Cancer Hospital from December 2018 to June 2020.The localized CT images and target organs at risk and other structural data were collected.Two radiotherapy plans,VMAT and TD,were designed for the same patient,and the dosimetry differences of target areas and organs at risk were compared and analyzed between the two groups.Results In terms of target dosimetry,there were statistically significant differences in the D_(2%)[(59.99±0.19)Gy vs.(59.55±0.51)Gy,t=4.09,P<0.001],D_(98%)[(57.19±0.08)Gy vs.(57.46±0.22)Gy,t=-5.10,P<0.001],conformal index(CI)(0.76±0.05 vs.0.58±0.13,t=8.19,P<0.001)and homogeneity index(HI)(0.05±0.00 vs.0.04±0.01,t=4.89,P<0.001)of the planning gross tumor volume(PGTV)between VMAT and TD plans.However,there was no statistically significant difference in the D_(50%)[(58.73±0.10)Gy vs.(58.73±0.24)Gy,t=-0.03,P=0.974].There were statistically significant differences in the D_(50%)[(52.21±0.33)Gy vs.(53.00±0.72)Gy,t=-4.81,P<0.001],D_(98%)[(48.44±0.43)Gy vs.(49.09±0.21)Gy,t=-6.80,P<0.001],CI(0.83±0.06 vs.0.67±0.06,t=10.52,P<0.001)and HI(0.20±0.01 vs.0.19±0.01,t=8.75,P<0.001)of the planned target volume(PTV)between the two plans.However,there was no statistically significant difference in the D_(2%)[(59.01±0.45)Gy vs.(59.00±0.48)Gy,t=0.22,P=0.830].In terms of organs at risk,there were statistically significant differences in the V20[(18.81±2.86)%vs.(22.03±1.91)%,t=-5.36,P<0.001]and D_(mean)[(11.66±1.32)Gy vs.(12.85±1.46)Gy,t=-4.10,P=0.007]of left lung,V5[(5.70±2.90)%vs.(0.30±0.13)%,t=16.44,P<0.001]and D_(mean)[(2.45±0.29)Gy vs.(0.43±0.14)Gy,t=9.09,P<0.001]of right lung,D_(mean)[(3.22±0.72)Gy vs.(1.69±0.80)Gy,t=5.41,P<0.001]of right breast,D_(2%)[(5.37±1.97)Gy vs.(0.46±0.09)Gy,t=11.75,P<0.001]of cord between VMAT and TD plans.There were no significant differences in the V5 of left lung[(53.00±5.99)%vs.(50.00±7.69)%,t=1.91,P=0.061],V5 of right breast[(11.51±4.60)%vs.(8.06±3.49)%,t=1.59,P=0.120],V30[(1.49±0.69)%vs.(1.51±0.71)%,t=-0.06,P=0.952]and D_(mean)[(3.99±0.97)Gy vs.(3.90±1.03)Gy,t=0.56,P=0.581]of heart between the two plans.Conclusion TD and VMAT can meet the clinical dosimetry requirements for patients with left breast cancer after breast-conserving surgery.However,the two techniques have their own characteristics.VMAT has better conformity and TD has better uniformity.TD is significantly better than VMAT in protecting the right lung,right breast and spinal cord of healthy organs at risk.VMAT is better in protecting the left lung.Both VMAT and TD basically achieve the same protection for heart.