直肠癌IMRT中患者体重下降与位移误差的相关性研究

目的 研究因放疗反应引起的直肠癌患者体重随时间变化趋势及位移误差与体重下降关系并以此制定不同治疗时期图像引导策略。方法 选取2016年间术后直肠癌患者24例。疗前记录每次体重、每周不同频率CBCT,并与计划CT进行在线配准,得到疗前位移误差。配对t检验差异,Pearson法分析位移误差与体重下降关系。结果 24例患者共进行456次体重监测,456次CBCT与配准。2例患者因中断治疗而排除。第1、2周体重无明显变化,第3周体重平均下降1.53 kg,第4周平均下降2.48 kg,第5周平均下降3.24 kg。由CBCT在线配准得到上下、前后、左右方向平均位移误差分别为0.19、0.20、0.18 cm (第1周),0.18、0.17、0.15 cm (第2周), 0.20、0.22、0.21 cm (第3周),0.19、0.25、0.24 cm (第4周),0.34、0.33、0.31 cm (第5周)。相关分析显示体重下降会增大位移误差(上下,前后,左右方向的P值分别为:0.140、0.046、0.044)。结论 直肠癌放疗患者后期尤其第5周体重呈明显下降趋势并影响位移误差,建议在直肠癌治疗日程到第4、5周时密切监测患者体重下降趋势,酌情于治疗前增加CBCT图像引导次数,以确保治疗精准化和最优化。

Correlation between weight loss and setup errors in intensity-modulated radiotherapy for rectal cancer

Objective To investigate the change in body weight over time in rectal cancer patients receiving radiotherapy and the correlation between setup errors and weight loss,and to establish the image-guided radiotherapy regimens in different periods of treatment.Methods A total of 24 postoperative patients with rectal cancer admitted to our hospital in 2016 were selected.Before each fraction of radiotherapy,the body weight was recorded,and the patients underwent cone-beam computed tomography (CBCT) with different frequencies in every week.The planning CT was matched with CBCT to obtain setup errors.The paired t test was used for difference analysis;the Pearson method was used to analyze the correlation between setup errors and weight loss.Results Body weight was measured 456 times in the 24 patients,and these patients underwent CBCT scans and image registration 456 times.Two patients were excluded because of treatment discontinuance.In the first and second weeks,there was no significant change in body weight.In the third week,the mean weight loss was 1.53 kg.In the fourth week,the mean weight loss was 2.48 kg.In the fifth week,the mean weight loss was 3.24 kg.The setup errors obtained by CBCT image registration in the superior-inferior (SI),anterior-posterior (AP),and left-right (LR) directions were 0.19 cm,0.20 cm,and 0.18 cm,respectively,in the first week,0.18 cm,0.17 cm,and 0.15 cm,respectively,in the second week,0.20 cm,0.22 cm,and 0.21 cm,respectively,in the third week,0.19 cm,0.25 cm,0.24 cm,respectively,in the fourth week,and 0.34 cm,0.33 cm,and 0.31 cm,respectively,in the fifth week.The Pearson correlation analysis showed that weight loss increased the setup errors,with P values of 0.140,0.046,and 0.044 in the SI,AP,and LR directions,respectively.Conclusions For rectal cancer patients receiving radiotherapy,the body weight decreases significantly in the late period (especially in the fifth week),which influences the setup errors.Therefore,in the fourth and fifth weeks of radiotherapy for rectal cancer,the weight loss should be closely monitored,and the number of CBCT scans can be increased before the treatment fraction to ensure the accuracy and optimization of treatment.