The Value Of MR Diffusion-weighted Imaging And Functional Diffusion Map In Evaluation Of The Response To Preoperative Chemoradiation In Locally Advanced Rectal Cancer

Objective:To explore the value of apparent diffusion coefficient and functional diffusion map in predicting and monitoring therapeutic effect of preoperative chemoradiation therapy(CRT)in locally advanced rectal cancer,in order to provide reliable imaging basis for clinical individual treatment.Clinical data and methods:32 patients with locally advanced rectal cancer undergoing preoperative CRT were recruited to the study.Conventional MRI and DWI was performed on a 1.5T MR scanner in all patients at the time node of pre-therapy(node A),the end of the 1st(node B),2nd week of therapy(node C)and post-therapy(node D),respectively.The corresponding ADC maps and functional diffusion maps were produced on the workstation.Measure the tumor invasion depth and ADC value of the tumor and calculate the increase and change rate of ADC value,fDM’s Red voxel proportion change at every monitor time point.According to Dworak’s tumor regression grade(TRG)criterion the patients were divided into the non-sensitive group(TRG0 – TRG2)and sensitive group(TRG3 and TRG4).Two independent samples T-test,Wilcoxon rank sum test,one-way anova analysis,Kruskal-Wallis test and ROC curve were used for the data statistical analysis.Results:1.In the process of treatment,the tumor invasion depth decreased gradually while the ADC value was in a rising tendency.Two indicators respectively were significantly different at different therapy time point(P<0.05).The tumor’s regression was focus on the middle and late period of preoperative CRT,however the ADC Values showed significant change in the early stage of treatment.2.32 patients were divided into sensitive group(n=20)and non-sensitive group(n=12).Sensitive group’s tumor ADC values at the different therapy time point show significant differences(P<0.05),so did non-sensitive group’s tumor ADC values(P<0.05).Two group’s tumor ADC values were increasing gradually.Comparing node A group’s,node B group’s,node C group’s tumor ADC values between sensitive group and non-sensitive group,there were no statistical differences(P>0.05).The tumor ADC values of sensitive group at node D are higher than non-sensitive group’s and show obvious differences.Comparing the △ADC1(the difference of ADC value between node A and node B),△ADC2(the difference of ADC value between node B and node C)and △ADC3(the difference of ADC value between node C and node D)respectively between sensitive group and non-sensitive group,sensitive group’s △ADC1,△ADC2,△ADC3 are higher than non-sensitive group’s.△ADC1 and △ADC3 show significant differences between sensitive group and non-sensitive group(P<0.05),while △ADC2 do not(P>0.05).3.Regard the increase and the change rate of ADC value,fDM’s Red voxel proportion change at 1st week respectively as diagnostic marker of tumor sensibility.When ADC value at 1st week increased larger than 0.128×10-3mm2/s,the sensitivity was 70.0% and the specificity was 75.0% respectively,the area under curve(AUC)was 0.754(95% confidence interval:0.570~0.888).When the change rate of ADC value at 1st week increased larger than 13.46%,the sensitivity was75.0% and specificity was 66.7% respectively,the AUC was 0.733(95% confidence interval:0.548~0.873).When the fDM’s Red voxel proportion change at 1st week increased larger than 18.78%,the sensitivity was 85.0% and specificity was 91.7% respectively,the AUC was 0.875(95% confidence interval:0.710~0.965).Comparing the AUC between any two diagnostic marker above,there are no statistical difference.Conclusion:1.ADC value can be used as early and quantitative marker for evaluating therapeutic effect of preoperative CRT in advanced rectal carcinoma by reflecting the change of tumor’s micro-environment and it has distinct advantage than the traditional evaluating method by measuring the tumor morphological change.2.To some extend,the increase and the change rate of ADC value can indicate the tumor sensitivity in the process of preoperative CRT,which provide guidance for the adjustment of treatment.3.The increase and the change rate of ADC value,fDM’s Red voxel proportion change at 1st week respectively as diagnostic marker of tumor sensibility have decent diagnostic efficiency and the fDM’s Red voxel proportion change has higher sensitivity,specificity and more area under curve.