目的: 利用锥形束 CT(cone-beam CT,CBCT)探究乳腺癌保乳术后胸壁野加锁骨上野联合放疗时分别采用同一等中心计划和双中心计划的差异,为临床治疗提供参考。方法: 收集行保乳术后接受三维适形放射治疗(3D-CRT)照射胸壁和锁骨上野同一等中心患者及双等中心患者各10例,患者均应用CBCT记录各中心点X(左右)、Y(头脚)、Z(前后)三线性方向摆位误差数据(每周一次),保持原始计划条件一致,使用摆位误差修正中心点坐标并带入计划系统,生成误差计划,在原计划90%的靶区体积达到90%处方剂量的前提下,评估由误差引起的单中心和双中心两种不同放疗计划的计划靶区(planning target volume,PTV)和危及器官实际剂量学参数变化及两种计划治疗学参数差异。结果: 单中心与双中心误差计划相比,靶区PTV方面最大剂量Dmax(t=-4.744,P＜0.001)、平均剂量Dmean(t=-2.288,P=0.025)、90%处方剂量包绕的体积百分比V90%(t=-3.216,P=0.002)、110%处方剂量包绕的体积百分比V110%(Z=-3.838,P＜0.001)、热点剂量D1cc(t=-6.051,P＜0.001),单中心组低于双中心组,差异有统计学意义(P＜0.05)。危及器官方面对侧肺500 cGy剂量所包绕体积百分比V5(Z=-2.373,P=0.018)、Dmean(Z=-2.534,P=0.011)、脊髓Dmax(t=-4.417,P＜0.001)、甲状腺Dmean(t=-4.535,P＜0.001)为双中心组高于单中心组,差异有统计学意义(P＜0.05),其余参数差异无统计学意义。治疗参数方面治疗时间(t=-2.621,P=0.010)为双中心组高于单中心组,差异有统计学意义(P＜0.05),机器跳数参数差异无统计学意义。结论: 乳腺癌保乳术后放疗胸壁野联合锁骨上野进行放射治疗同一等中心计划在减小误差导致靶区内高量,剂量热点及危及器官保护等方面优于双等中心计划。

Objective: To investigate the difference between the same isocenter plan and dual-center plan when using cone-beam CT (CBCT) for breast cancer breast-conserving surgery with chest wall and supraclavicular fields combined radiotherapy for reference of clinical treatment. Methods: Ten patients with the same isocenter and 10 patients with double isocenters were collected after breast-conserving surgery with three-dimensional conformal radiation therapy (3D-CRT) irradiation of the chest wall and supraclavicular field, and the patients applied CBCT to record the positional error data of X (left and right), Y (head and foot), and Z (front and back) in the three linear directions of the center points (once a week) to keep the same conditions of the original plan, and the centers were corrected using the positional error to generate error plans. The centroid coordinates were corrected using the positioning errors and brought into the planning system to generate an error plan. Under the premise that 90% of the target volume of the original plan reached 90% of the prescribed dose, the changes in the actual dosimetric parameters of the planning target volume (PTV) and organs at risk and the differences in the therapeutic parameters of the two types of single-center and dual-center radiotherapy plans caused by the errors were evaluated. Results: Compared with single-center and double-center error plans, the maximum dose Dmax (t=-4.744, P＜ 0.001), mean dose Dmean (t=-2.288, P=0.025), percentage of volume encompassed by 90% of the prescribed dose V90% (t=-3.216, P=0.002), and 110% of the volume encompassed by 110% of the prescribed dose (Z=-3.838, P＜0.001), and hotspot dose D1cc (t=-6.051, P＜0.001) were lower in the single-center group than those in the double -center group, and the difference was statistically significant (P＜0.05). In terms of organs at risk, the percentage of volume encompassed by 500 cGy dose in the contralateral lung, V5 (Z=-2.373, P=0.018), Dmean (Z=-2.534, P=0.011), spinal cord Dmax (=-4.417, P＜0.001), and thyroid Dmean (t=-4.535, P＜0.001) were higher in the two-center group than those in the single-center group, the difference was statistically significant (P＜0.05), and the differences in the remaining parameters were not statistically significant. In terms of treatment parameters, the treatment time (t=-2.621, P=0.010) was higher in the two-center group than in the single-center group, and the difference was statistically significant (P＜0.05), while the difference in the parameters of the number of machine jumps was not statistically significant. Conclusion: The same isocenter radiotherapy plan of chest wall field combined with supraclavicular field after breast conserving surgery for breast cancer is superior to the double isocenter radiotherapy plan in reducing the error leading to high dose in the target area, dose hotspots and protection of organs at risk.