The Value Of DWI And DCE-MRI In Predicting The Therapeutic Effect Of Neoadjuvant Chemoradiation Therapy In Locally Advanced Rectal Cancer

Objective: To evaluate the efficacy of diffusion-weighted imaging（DWI）and dynamic contrast enhanced magnetic resonance imaging（DCE-MRI）in predicting T-downstaging of locally advanced rectal cancer（LARC）after neoadjuvant chemoradiation therapy（CRT）.Materials and Methods: Thirty patients（17 male,13 female,median age 65 years）with LARC who underwent preoperative CRT and subsequent total mesorectal excision（TME）surgery in Cangzhou Center Hospital between January 2016 and February 2017 were included in this study.All patients underwent MRIs within one week before the CRT（pre-CRT）,at the end of the 1st week after CRT（post-CRT）and within one week before the TME surgery（pre-TME）respectively.ADC and K^trans values were measured in the rectal cancer lesions of all the 30 patients.According to the American Joint Committee on Cancer Staging（AJCC）TNM staging criteria,the results of postoperative pathological T staging for all the 30 patients were compared with those of pre-CRT MRI T staging.Patients with decreased T staging is defined as T-downstaging group,whereas patients with the same or higher T staging is defined as non-T-downstaging group.SPSS 20.0 statistical software was used for statistical analysis.Repetitive measure analysis of variance（ANOVA）was applied to analyze the differences of ADC and K^trans value among the different time points in population and within each of the two groups respectively;The least significant difference was applied to compare each of the two groups.The differences of ADC and K^trans value between the two groups at the different time points and the rate of increase of the post-CRT ADC and K^trans value between the two groups were compared with Independent sample t test and Mann-Whitney test respectively.The efficacy in predicting T-downstaging by the rate of increase for the post-CRT ADC value and the pre-CRT K^trans value were evaluated respectively using receiver operating characteristic curve（ROC）.U test was applied to compare the dignostic performance.The sensitivity and specificity of using the combined application of the two parameters in predicting T-downstaging were also determined.A P value less than 0.05 was considered to indicate a statistically significant difference.Results: Among the 30 patients enrolled into the study,19 were diagnosed as T-downstaging and 11 as T-non-downstaging.There was a trend of gradual increase of the ADC values in the population and in both T-downstaging and T-non-downstaging group.In the population,the difference of the ADC values among pre-CRT [（0.99±0.05）×10^-3 mm²/s],post-CRT [（1.16±0.07）×10^-3 mm²/s],and pre-TME [（1.23±0.07）×10^-3 mm²/s] was statistically significant（F=202.698,P<0.05）.In T-downstaging group,the difference of the ADC values among pre-CRT [（0.98±0.05）×10^-3 mm²/s],post-CRT [（1.17±0.08）×10^-3 mm²/s],and pre-TME [（1.25±0.06）×10^-3 mm²/s] was statistically significant（F=223.162,P<0.05）.In T-non-downstaging group,the difference of the ADC values among pre-CRT [（1.01±0.04）×10^-3 mm²/s],post-CRT [（1.13±0.04）×10^-3 mm²/s],and pre-TME [（1.2±0.09）×10^-3 mm²/s] was statistically significant（F=49.82,P<0.05）.None of the difference of ADC value between the two groups at different time points had statistical significance（P>0.05）.The difference of the rate of increase for post-CRT ADC value between the two groups was statistically significant（Z=-2.819,P=0.005）.Using the rate of increase for post-CRT ADC value as the diagnostic marker of T-downstaging,and 15.1% as the threshold,the sensitivity and specificity was 73.7% and 81.8% respectively,and the area under the ROC curve（AUC）was 0.813（95%confidence interval: 0.662 to 0.965）.After CRT,K^trans values increased at first and then reduced in the population and in both T-downstaging and T-non-downstaging group.In the population,the difference of K^trans values among pre-CRT [（1.21±0.23）/min],post-CRT [（1.36±0.32）/min],and pre-TME [（0.86±0.19）/min] was statistically significant（F=77.348,P<0.05）.In T-downstaging group,the difference of K^trans values among pre-CRT [（1.28±0.14）/min],post-CRT [（1.44±0.27）/min],and pre-TME [（0.90±0.19）/min] was statistically significant（F=48.026,P<0.05）.In T-non-downstaging,the difference of the K^trans values among pre-CRT [（1.08±0.30）/min],post-CRT [（123±0.36）/min],and pre-TME [（0.78±0.15）/min] was statistically significant（F=28.941,P<0.05）.The difference of the pre-CRT K^trans value between the two groups was statistically significant（t=-2.454,P<0.05）.None of the difference of K^trans value between the two groups was statistically significant at the other two time points（P>0.05）.Using the pre-CRT K^trans value as the diagnostic marker of T-downstaging,and 1.17/min as the threshold,the sensitivity and specificity was 73.7% and 72.7% respectively,the AUC was 0.775（95%confidence interval: 0.583 to 0.968）.There was no significant statistically difference of the efficacy in predicting T-downstaging by the rate of increase for the post-CRT ADC value and the pre-CRT K^trans value（Z=-1.000,P=0.317）.When the rate of increase for post-CRT ADC value and the pre-CRT K^trans value are combined,the sensitivity raised to 93.1%,and the detection rate of T-downstaging improved.Conclusion: Both the rate of increase for post-CRT ADC value and the pre-CRT K^trans value had a definite accuracy in predicting T-downstaging of LARC after CRT.When the two parameters are combined,the diagnostic sensitivity maybe improved.