前列腺癌碳离子治疗直肠剂量体积直方图预测模型

Prediction model of local effect model-based rectal dose volume histogram in prostate cancer patients treated with carbon ion radiotherapy

目的基于日本经验建立局部效应模型(LEM)下前列腺癌碳离子治疗直肠剂量体积直方图(DVH)预测模型,为临床降低直肠不良反应发生率提供参考。方法收集局限期前列腺癌患者计划CT图像76例,采用微剂量动力模型(MKM)进行治疗计划;然后,基于与MKM计划相同的射野,采用LEM重新计算生物剂量获得LEM计划,并在LEM计划中提取直肠几何特征及DVH参数。采用线性回归法对其中61例计划信息进行建模,余15例计划用于验证。结果61例患者计划靶体积沿左右方向外扩1 cm后与直肠交叠部分体积同直肠体积比值可作为预测直肠DVH的特征参数。15例患者预测DVH同LEM计划DVH的拟合度优(R^(2)=0.964),基于预测DVH进一步预测直肠不良反应与基于LEM计划DVH预测直肠不良反应的结果一致。结论线性回归方法可建立较为准确的前列腺癌碳离子治疗直肠DVH预测模型,可能为临床降低直肠不良反应发生率提供一定参考,还有待于临床大样本数据进一步验证。

Objective To establish a local effect model(LEM)-based rectal dose volume histogram(DVH)prediction model in prostate cancer patients treated with carbon ion therapy based on Japanese experience,aiming to provide reference for clinically reducing the incidence of rectal adverse reactions.Methods The planning CT data of 76 patients with prostate cancer were collected.The microdosimetric kinetic model(MKM)was used for initial planning,and the LEM was selected to recalculate the biological dose based on the same fields to MKM.Then,the geometric features and DVH of the rectum were extracted from the LEM plans.The planning data of 61 cases were used to establish the prediction model with linear regression and the other 15 cases were used for validation.Results The ratio of the overlapped volume between the rectum and the region of interest(ROI)expended from planning target volume by 1 cm along the left and right directions of the rectum could be proved to be the characteristic parameters for linear regression.The mean goodness-of-fit R^(2) of predicted and LEM plan-based DVH of 15 cases was 0.964.The results of predicted rectal adverse reactions based on predicted DVH were consistent with those of LEM plan-based DVH.Conclusions The linear regression method used in this study can establish an accurate prediction model of rectal DVH,which may provide certain reference for reducing the incidence of rectal adverse reactions.Nevertheless,the findings remain to be further verified by clinical trials with larger sample size.