乳腺癌术后热塑体膜固定放疗中摆位误差及安全性研究

Study of setup error and safety of postoperative radiotherapy for breast cancer with a thermoplastic body mask immobilization

目的探讨乳腺癌术后放射治疗(简称放疗)采用仰卧位热塑体膜固定后摆位误差及安全性。方法收集2020年9月至2021年6月该院放疗科收治的58例乳腺癌术后放疗患者,放疗均采用仰卧位热塑体膜固定。利用锥形束CT(CBCT)图像与定位CT图像对比,记录三维方向上的位移,分析影响摆位误差的因素并计算临床靶区(CTV)外扩至计划靶区(PTV)的边界,以及急性放射性皮炎的发生率。结果全组患者共403套CBCT图像,中位数7套(5~11套)。X、Y、Z方向的摆位误差分别为(0.17±0.10)、(0.30±0.22)、(0.16±0.08)cm;X、Y、Z方向CTV外扩至PTV边界分别为0.27、0.35、0.28 cm。CBCT>7次与CBCT≤7次的患者在Y轴方向比较,差异有统计学意义[(0.33±0.07)cm vs.(0.28±0.07)cm,P=0.009]。不同手术方式、病变位置及体重指数间摆位误差比较差异均无统计学意义(P>0.05)。全组1、2级放射性皮炎分别为96.55%、3.45%,无3级以上放射性皮炎。结论乳腺癌术后热塑体膜固定安全可行,推荐PTV三维外扩边界最少为0.35 cm。

Objective To investigate the setup errors and safety of postoperative radiotherapy for breast cancer with a thermoplastic body mask immobilization in the supine position.Methods Fifty-eight patients with breast cancer receiving postoperative radiotherapy in the radiotherapy department of this hospital from September 2020 to June 2021 were collected.The thermoplastic body mask immobilization was used for radiotherapy.The comparison between cone-beam CT(CBCT)images and location CT images was used,and the displacements in three-dimensional direction were recorded.The factors affecting the setup errors were analyzed and the margin from clinical target volume(CTV)to planning target volume(PTV)was calculated.And the occurrence rate of acute radiation dermatitis was calculated.Results There were 403 sets of CBCT images with a median of 7 sets(ranging from 5 to 11 sets)in all cases.The setup errors in X,Y and Z directions were(0.17±0.10),(0.30±0.22)and(0.16±0.08)cm,respectively.The margin from CTV to PTV in X,Y and Z directions were 0.27,0.35 and 0.28cm,respectively.The comparison between the patients with CBCT>7 times and the patients with CBCT≤7 times in the Y axis direction showed the statistical difference[(0.33±0.07)cm vs.(0.28±0.07)cm,P=0.009].There were no statistically significant differences in the setup errors among the patients with different operation methods,different lesion locations and different body mass indexes(all P>0.05).The grade 1 and grade 2 radiation dermatitis in the whole group were 96.55%and 3.45%respectively.There was no case of more than grade 3 radiation dermatitis.Conclusion The postoperative thermoplastic body mask immobilization for breast cancer is safe and feasible.It is recommended that the external expansion margin of PTV should be at least 0.35 cm in three-dimensional directions.