Predictors of Pathologic Complete Response in Rectal Cancer Patients Undergoing Total Mesorectal Excision after Preoperative Chemoradiation

Preoperative chemoradiotherapy (CRT) is the standard of care for patients with stage II and III rectal cancer. This strategy leads to pathologic complete response (pCR) in a significant number of patients. Factors predictive of pCR are currently being extensively investigated. The aim of this study was to analyze clinical factors that might be predictive of pCR. This study was a retrospective analysis of rectal cancer patients from January 2004 through December 2012. A total of 332 stage II and III patients with middle and low rectal cancer (≤10cm) who received CRT and underwent curative total mesorectal excision were eligible. The median radiation dose was 50.4Gy, and 72.6% of patients received infusional 5-fluorouracil with leucovorin, whereas 19.6% of patients received TS-1 with irinotecan, and 7.8% of patients received xeloda only. Pathologic complete response was confirmed by using pathologic specimens and analyzed based on predictive clinical factors. Among the 332 patients, 27.4% (n=91) achieved pCR. Age, sex, body mass index, clinical T and N stages, tumor differentiation, the chemotherapy agent for CRT, and the time interval between CRT and surgery did not differ between the pCR and non-pCR groups. Carcinoembryogenic antigen (CEA) levels before CRT were 4.61±7.38ng/mL in the pCR group and 10.49±23.83ng/mL in the non-pCR group (P=0.035). Post-CRT CEA levels were 1.4±1.07ng/mL in the pCR group and 2.16±2.8ng/mL in the non-pCR group (P=0.014), and the proportion of middle rectal cancer patients was higher in pCR group (54.9%, P=0.028). The results from multivariate logistic regression analysis indicated that higher tumor location (odds ratio 2.151; P=0.003) and low post-CRT CEA level (odds ratio 0.789; P=0.04) were independent predictive factors for pCR. Tumor location and post-CRT CEA level were predictive factors in pCR for rectal cancer patients. Therefore, these factors may be important determinants in achieving pCR, and may also be used to predict oncologic outcomes.