The role of apparent diffusion coefficient value in evaluation of the response to preoperative chemoradiation in rectal carcinoma / 中华放射学杂志

ABSTRACT

Objective To assess response of rectal carcinoma to preoperative chemoradiation therapy(CRT)using DWI and tumor ADC values,and to investigate the value of ADC in predicting and monitoring therapeutic effect of CRT.Methods Twenty-six patients with primary rectal carcinoma undergoing preoperative CRT were recruited to the study.DWI was performed on a 1.5 T MR scanner in all patients at the time point of pre-therapy,the end of the 1st,2nd week of therapy and pre-operation,respectively.ADC values of the tumors were calculated on the workstation.Randomized block design was applied to analyze change in ADCs following treatment Results All patients were divided into T-downstaging group(n=12)and T-non-downstaging group(n=14).In T-downstaging group,the mean tumor ADC values were(1.10±0.13)×10~(-3),(1.32±0.19)×10~(-3),(1.35±0.13)×10~(-3),(1.32±1.00)×10~(-3) mm~2/s at the time point of pretreatment,week 1,week 2,pre-operation,respectively(F=16.420,P＜0.01).The mean tumor ADC value in T-non-downstaging had a slight increase from(1.16±0.16)×10~(-3) mm~2/s to(1.23±0.13)×10~(-3) mm~2/s at the time of week 1(P＞0.05).The ADC value in T-non-downstaging group continuously increased to(1.30±0.16)×10~(-3) mm~2/s at the end of the 2nd week of CRT(F=5.023,P＜0.01)and appeared statistical difference.The evolution of tumor ADC values in the two groups was significantly different.Early increases in tumor ADC were observed in T-downstaging group.Regarding the increase percentage of ADC value at 1st week as a diagnostic marker of tumor downstaging,when it was set as 11.6%,the sensitivity,specificity,positive predictive value and negative predictive value is 75.0%,78.6%,75.0% and 78.6% respectively,the area under curve(Az)was 0.774(95% confidence interval0.583 to 0.964).Conclusions An early significant increase of mean tumor ADC value in rectal carcinoma has a potential to predict therapeutic effect of CRT.One week after beginning CRT is an early time point to monitor therapy efficacy.