磁共振肿瘤退缩分级和表观弥散系数对局部进展期直肠癌新辅助治疗后病理完全缓解的预测价值

Predictive value of combination of MRI tumor regression grade and apparent diffusion coefficient for pathological complete remission after neoadjuvant treatment of locally advanced rectal cancer

目的盆腔高分辨磁共振成像(MRI)现已成为评估局部进展期直肠癌新辅助治疗效果的标准手段。但这种基于T2加权成像(T2WI)的传统形态学定性评估方式对于病理完全缓解(pCR)的预测效果欠佳。本研究旨在探讨在基于T2WI评估的磁共振肿瘤退缩分级(mrTRG)的基础上,加入基于弥散加权成像(DWI)的表观弥散系数(ADC值),能否改善对pCR的预测价值。方法本研究为诊断性研究,回顾性分析2017年1月至2019年12月期间在昆明医科大学第一附属医院接受新辅助放化疗加根治性手术治疗的134例局部进展期直肠癌的临床病理资料。所有病例于新辅助放化疗前及治疗结束后8周进行MRI检查,两名放射科医师分别在T2WI和DWI图像上绘制感兴趣区域,评估mrTRG并计算平均ADC值。采用受试者操作特征(ROC)方法评价mrTRG和平均ADC值对pCR的预测价值。结果本组134例患者中男性85例,女性49例,中位年龄58(28~82)岁。新辅助治疗后,MRI评估提示21例(15.7%)获临床完全缓解(cCR,即mrTRG 1~2级);术后病理提示31例(23.1%)患者获pCR。两名阅片者对mrTRG和ADC值的评估具有很好的一致性,组内相关系数分别为0.83(95%CI:0.703~0.881)和0.96(95%CI:0.989~0.996)。mrTRG与pCR呈负相关(rs=-0.505,P<0.01),平均ADC值与pCR呈正相关(rs=0.693,P<0.01)。ROC曲线显示,单用mrTRG对pCR具有中等预测价值,曲线下面积(AUC)0.832(95%CI:0.743~0.921);平均ADC值对pCR具有较高的预测价值,AUC为0.906(95%CI:0.869~0.962);而两者组合模型的pCR预测价值显著优于单用mrTRG(P=0.015),AUC为0.908(95%CI:0.849~0.968)。结论mrTRG与平均ADC值都可作为评估局部进展期直肠癌新辅助放化疗治疗效果的无创性方法。在mrTRG的基础上加入平均ADC值能够带来更好的pCR预测表现。

Objective Pelvic high-resolution magnetic resonance imaging(MRI)has now become a standard method for evaluating the efficacy of neoadjuvant treatment for locally advanced rectal cancer(LARC).However,this traditional morphological qualitative assessment method based on T2-weighted imaging(T2WI)is not effective in predicting pathological complete remission(pCR).The purpose of this study is to investigate whether combining the magnetic resonance tumor regression grade(mrTRG)with apparent diffusion coefficient(ADC)can improve diagnostic value for pCR after preoperative neoadjuvant chemoradiotherapy(nCRT)of LARC.Methods This was a diagnostic study.Clinicopathological data of 134 LARC patients who received nCRT and radical surgery in the First Affiliated Hospital of Kunming Medical University from January 2017 to December 2019 were retrospectively analyzed.All the patients underwent MRI which included T2WI and DWI sequences before and 8 weeks after nCRT.Two radiologists independently drew ROIs on T2WI and DWI to estimate mrTRG stage and calculate the mean ADC value.Receiver operating characteristics(ROC)method was applied to evaluate the predict value of mrTRG combined with mean ADC value for pCR.Results Of 134 LARC patients,85 were male and 49 were female with median age of 58(28-82)years.After nCRT,MRI suggested 21 patients(15.7%)had clinical complete remission(cCR),e.g.mrTRG stage 1-2.Postoperative pathology revealed 31(23.1%)patients had pCR.The evaluations of mrTRG and ADC value by the two readers were highly consistent,and the intra-group correlation coefficients were 0.83(95%CI:0.703-0.881)and 0.96(95%CI:0.989-0.996),respectively.There was a negative correlation between mrTRG and pCR(rs=-0.505,P<0.01),and a positive correlation between mean ADC value and pCR(rs=0.693,P<0.01).The ROC curve showed that mrTRG alone had a medium predictive value for pCR,with an area under the curve(AUC)of 0.832(95%CI:0.743-0.921);the mean ADC value had a higher predictive value for pCR,with AUC of 0.906(95%CI:0.869-0.962).The predictive value of the combined model of mrTRG and ADC value for pCR was significantly better than that of mrTRG alone(P=0.015),and the AUC was 0.908(95%CI:0.849-0.968).Conclusion Both mrTRG and mean ADC value can be non-invasive methods to predict the efficacy of nCRT for LARC.Combining the mean ADC value with mrTRG can result in better pCR prediction.