Study Of Predictor Factors For Pathologic Complete Response After Neoadjuvant Chemoradiotherapy For Locally Advanced Rectal Cancer

Objective This study evaluates clinical and Riadiological factors associated with pathologic complete response(p CR) after preoperative neoadjuvant chemoradiation for locally advanced rectal cancer.Methods We retrospectively analyzed 265 patients with stage II and III(the 7th version of AJCC) rectal cancer between January 2011 to June 2013. All patients underwent neoadjuvant concurrent chemoradiotherapy(CCRT) followed by surgery with/or without induction chemotherapy during the interval between the complete of CCRT and surgery. A total of 50 patients(18.9%) achieved p CR. Another 50 non-p CR patients were selected to be matched the 50 p CR patients. All of the 100 average ADC values of pre- and post-CRT were measured by Diffusion- weighted MRI technology. Clinical and Radiological factor were analyzed by univariate analysis,Logistic multivariate analysis and receiver operating characteristic curve with p CR.Result Pretreatment CEA(P=0.017), pretreatment T stage(P=0.001), interval of CRT to surgery(P<0.001), pretreament tumor maximum size(P=0.040), pretreatment ADC value(p=0.003), the percentage of Increase in tumor ADC(P<0.001) were significantly associated with pathologic complete response in the univariate analysis. Pretreatment CEA(P=0.047 OR 0.447) and Interval of CRT to surgery(P=0.005 OR 2.94)were significant predictors of pathologic complete response in the multivariate analysis. When stratifying for smoking status, low CEA level was significantly associated with pathologic complete response only in the group of nonsmokers(P=0.044).The predictive accuracy of Pretreatment ADC value and I the percentage of Increase in tumor ADC are 60% and 78%, respectively. Lower than Pretreatment ADC value of 0.866 ×10-3mm2/s and(or)higher than Increase ratio of ADC of 0.580 were significant predictors of pathologic complete response,especially the predictive accuracy of Increase ratio is higher.Conclusion For Locally Advanced Rectal Cancer, p CR could be achieved after Neoadjuvant Therapy.Lower CEA level and longer Interval of CRT to surgery r were significant predictors of pathologic complete response, but low CEA level was only significantly associated with pathologic complete response in the group of nonsmokers. Pretreatment ADC value and Increase ratio of ADC have medium diagnostic value for p CR of locally advanced rectal cancer after neoadjuvant therapy.