CEA - A predictor for pathologic complete response after neoadjuvant therapy for rectal cancer

Background: Preoperative chemoradiation therapy in patients with rectal cancer results in pathologic complete response in approximately 10% to 30% of patients. Accurate predictive factors for obtaining pathologic complete response would likely influence the selection of patients best treated by chemoradiation therapy as the primary treatment without radical surgery. Objective: The aim of this study was to evaluate the impact of tumor size, stage, location, circumferential extent, patient characteristics, and pretreatment CEA levels on the development of pathologic complete response after chemoradiation therapy. Design: This study is a retrospective review. Settings and Patients: Five hundred thirty patients treated with preoperative chemoradiation therapy and radical surgery for rectal adenocarcinoma between 1998 and 2011 were identified. A total of 469 patients remained after excluding patients with a history of pelvic radiation (n = 2), previous transanal endoscopic microsurgery or polypectomy of the primary lesion (n = 15), concurrent malignant tumor (n = 14), and no information about pre- or posttreatment T stage in the chart (n = 30). Preoperative CEA levels were available for 267 patients (57%). Interventions: Preoperative chemoradiation therapy and total mesorectal excision were performed in patients with rectal cancer. Main Outcome: The primary outcome measured was pathologic complete response. Results: Ninety-six patients (20%) were found to have a pathologic complete response in the operative specimen. Low pretreatment CEA (3.4 vs 9.6 ng/mL; p = 0.008) and smaller mean tumor size (4.2 vs 4.7 cm; p = 0.02) were significantly associated with pathologic complete response. Low CEA levels and interruption in chemoradiation therapy 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 = 0.02). Limitations: This study was limited by its retrospective design, missing CEA values, and lack of tumor regression grade assessment. Conclusions: We demonstrated an association between low pretreatment CEA levels, interruption in chemoradiation therapy, and pathologic complete response in patients treated with neoadjuvant chemoradiation therapy for locally advanced rectal cancer. The predictive value of CEA in smokers can be limited, and further studies are needed to evaluate the impact of smoking on the predictive value of CEA levels for pathologic complete response in rectal cancer.