Department of Radiation Oncology, Fudan University Shanghai Cancer Center, 270 DongAn Road, Shanghai, China.
Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, 200032, China.
Radiat Oncol. 2021 Aug 3;16(1):143. doi: 10.1186/s13014-021-01863-w.
To use cone-beam computed tomography (CBCT) imaging to determine the impacts of patient characteristics on the magnitude of geometric setup errors and obtain patient-specific planning target volume (PTV) margins from the correlated patient characteristics in whole breast irradiation (WBI).
Between January 2019 and December 2019, a total of 97 patients who underwent breast-conserving surgery, followed by intensity-modulated radiation therapy in WBI, were scanned with pre-treatment CBCT for the first three treatment fractions and weekly for the subsequent fractions. Setup errors in the left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions were recorded and analyzed with patient characteristics-including age, tumor location, body mass index (BMI), chest circumference (CC) and breast volume (BV)-to examine the predictors for setup errors and obtain specific PTV margins.
A total of 679 CBCT images from 97 patients were acquired for analysis. The mean setup errors for the whole group were 2.32 ± 1.21 mm, 3.71 ± 2.21 mm and 2.75 ± 1.56 mm in the LR, SI and AP directions, respectively. Patients' BMI, CC and BV were moderately associated with setup errors, especially in the SI directions (R = 0.40, 0.43 and 0.22, respectively). Setup errors in the SI directions for patients with BMI > 23.8 kg/m, CC > 89 cm and BV > 657 cm were 4.56 ± 2.59 mm, 4.77 ± 2.42 mm and 4.30 ± 2.43 mm, respectively, which were significantly greater than those of patients with BMI ≤ 23.8 kg/m, CC ≤ 89 cm and BV ≤ 657 cm (P < 0.05). Correspondingly, the calculated PTV margins in patients with BMI > 23.8 kg/m, CC > 89 cm and BV > 657 cm were 4.25/7.95/4.93 mm, 4.37/7.66/5.24 mm and 4.22/7.54/5.29 mm in the LR/SI/AP directions, respectively, compared with 3.64/4.64/5.09 mm, 3.31/4.50/4.82 mm and 3.29/5.74/4.73 mm for BMI ≤ 23.8 kg/m, CC ≤ 89 cm and BV ≤ 657 cm, respectively.
The magnitude of geometric setup errors was moderately correlated with BMI, CC and BV. It was recommended to set patient-specific PTV margins according to patient characteristics in the absence of daily image-guided treatment setup.
使用锥形束 CT（CBCT）成像来确定患者特征对几何摆位误差幅度的影响，并从全乳照射（WBI）中的相关患者特征获得患者特异性计划靶区（PTV）边界。
在 2019 年 1 月至 2019 年 12 月期间，共有 97 名接受保乳手术后接受 WBI 调强放疗的患者，在前三个治疗分次进行治疗前 CBCT 扫描，随后的分次每周进行扫描。记录左右（LR）、上下（SI）和前后（AP）方向的摆位误差，并结合患者特征（包括年龄、肿瘤位置、体重指数（BMI）、胸围（CC）和乳房体积（BV））进行分析，以检查摆位误差的预测因素并获得特定的 PTV 边界。
对 97 名患者的 679 张 CBCT 图像进行了分析。整个组的平均摆位误差在 LR、SI 和 AP 方向分别为 2.32±1.21mm、3.71±2.21mm 和 2.75±1.56mm。患者的 BMI、CC 和 BV 与摆位误差中度相关，尤其是在 SI 方向（R=0.40、0.43 和 0.22）。BMI>23.8kg/m、CC>89cm 和 BV>657cm 的患者在 SI 方向的摆位误差分别为 4.56±2.59mm、4.77±2.42mm 和 4.30±2.43mm，明显大于 BMI≤23.8kg/m、CC≤89cm 和 BV≤657cm 的患者（P<0.05）。相应地，BMI>23.8kg/m、CC>89cm 和 BV>657cm 的患者在 LR/SI/AP 方向的计算 PTV 边界分别为 4.25/7.95/4.93mm、4.37/7.66/5.24mm 和 4.22/7.54/5.29mm，而 BMI≤23.8kg/m、CC≤89cm 和 BV≤657cm 的患者分别为 3.64/4.64/5.09mm、3.31/4.50/4.82mm 和 3.29/5.74/4.73mm。
几何摆位误差的幅度与 BMI、CC 和 BV 中度相关。建议在没有每日图像引导治疗摆位的情况下，根据患者特征设置患者特异性 PTV 边界。
