Predictive factors of histological response after preoperative concomitant radiochemotherapy in middle and low rectal cancer

Objective: The aim of our study was to identify potential predictive factors beyond pathologic response after neoadjuvant radiochemotherapy. Patients and Methods: Between January 2009 and December 2014, 40 patients with rectal carcinoma were included in the study. The treatment consisted of radiation ranging between 39 and 50.4 Gy associated with a concomitant chemotherapy with capecitabine. The correlation between histological response (complete response and downstaging) and potential predictive factors was investigated. Results: Complete response was 15% (06 patients), tumor regression of 32.5% (13 patients), and the absence of tumor response of 52.5% (21 patients). In univariate analysis, the circumferential extension of the tumor was significantly associated with tumor downstaging (p = 0.007) and complete tumor response (p = 0.001). However, the delay between the RCT and the surgery was a significant predictor for downstaging (p = 0.02). Conclusion: the parietal circumferential extension was a potential predictor of pathologic complete response (pCR) and downstaging after neoadjuvant chemoradiation. The time between the radiochemotherapy and the surgery was a significant predictor for downstaging. Delaying surgery beyond 8 weeks seems to result in the highest probability of pCR. Keywords: Rectal cancer, adenocarcinoma, neoadjuvant radiochemotherapy, histologic response, predictive factors