Predicting Factors of Complete Pathological Response in Locally Advanced Rectal Cancer.

Background : Current treatment of choice for locally advanced rectal cancer is neoadjuvant chemoradiotherapy (neo-CRT) followed by surgical resection and adjuvant chemotherapy. Some patients may experience complete pathological response (cPR) after the neoadjuvant treatment. However, the predicting factors are still debated. Methods : In this registry-based retrospective cohort study, 258 patients with locally advanced rectal cancer were included. Patients were categorized into two groups with or without cPR. Logistic regression analysis was recruited to investigate the odds ratio for all independent variables, and those with significant results were included in multivariate regression analysis. Results : Achievement of cPR was 21.3%. The odds ratio of cPR was significantly lower when the tumor distance from the anal verge was>10 centimeters (OR=0.24, P =0.040). Also, the odds of cPR with N1 involvement in comparison with N0 involvement decreased for 0.41 ( P =0.043). It was also true for patients with N2 involvement in comparison with N0 involvement (OR=0.31, P =0.031). Higher odds ratio of cPR was observed in patients who underwent surgery in>12 weeks after neo-CRT (OR=2.9, P =0.022). Furthermore, the odds of cPR decreased for 0.9 with increasing in carcinoembryonic antigen (CEA) level ( P =0.044). Conclusion : Patients with rectal cancer in clinical stage II or lower, without the involvement of the lymphatic system at diagnosis, and with tumors located in the lower parts of the rectum, with lower levels of CEA, and longer duration between neo-CRT and surgery were more likely to achieve cPR after neo-CRT. With the current knowledge, the "wait and watch policy" is still debated and needs to be defined more precisely by upcoming studies.