Predicting rectal tumor response to neoadjuvant chemoradiotherapy using plasma levels of carcinoembryonic antigen (CEA): Results from a tertiary center in Iran

OBJECTIVES: Nonsurgical treatment of colorectal cancer, the third most prevalent cancer worldwide, through chemoradiotherapy (CRT) has been suggested to induce complete remission. Carcinoembryonic antigen (CEA) has been used as a candidate marker to predict treatment response. In this study, we aimed to assess the applicability of plasma levels of CEAs in predicting the response to CRT, particularly complete pathological response. METHODS: We designed a retrospective, cross-sectional study in which tumor stage and plasma levels of CEAs before and after neoadjuvant CRT were extracted from the medical records of patients with rectal tumors who underwent neoadjuvant chemoradiotherapy before surgery at Sina Hospital, Tehran, Iran from 2010 to 2015. RESULTS: Pre-CRT plasma levels of CEA positively correlated with tumor stage, and chemoradiotherapy significantly decreased plasma levels of CEA. Whereas lower pre-CRT plasma levels of CEA and tumor stage were significantly associated with complete response to CRT, post-CRT plasma levels of CEA showed no association with complete response. In addition, in ROC curve analysis, a CEA cut-off value of 2.6 ng/mL predicted complete response to CRT (specificity = 82.6%, sensitivity = 40.5%). CONCLUSION: Although several factors other than plasma levels of CEA and tumor stage are important in determining the response to CRT, preliminary plasma levels of CEA and tumor stage can be used as factors for determining complete response to neoadjuvant chemoradiotherapy in rectal cancer.