Prognostic Factor Associated with Pre- and Postneoadjuvant Carcinoembryonic Antigen in Patients with Middle and Low Rectal Adenocarcinoma and its Correlation with Pathological Findings

Abstract Colorectal cancer (CRC) ranks among the top three most common cancers in Brazil, and the carcinoembryonic antigen (CEA) is one of the most used and established methods for prognostic evaluation and recurrence monitoring in CRC patients. To analyze the pre- and postneoadjuvant levels of CEA in patients with middle or low rectal adenocarcinoma who underwent elective retossigmoidectomy with total mesorectal excision or abdominoperineal amputation of the rectum and to correlate the differences in pre- and postneoadjuvant CEA levels with the pathological staging. Retrospective analysis of patients over 18 years old who underwent elective retossigmoidectomy with total mesorectal excision or abdominoperineal resection of the rectum. Data regarding age, sex, type of surgery, absolute CEA values, and differences in pre- and postneoadjuvant CEA levels were evaluated. The electronic medical records of 77 patients diagnosed with middle or low rectal adenocarcinoma who underwent surgery were analyzed. The mean pre- and postneoadjuvant levels of CEA were of 15.21(± 26.41) ng/mL and 7.17(± 15.6) ng/mL respectively, indicating a statistically significant decrease (p = 0.00058). The cutoff value for the analysis of neoplastic invasion depth (T) was determined to be 4.9 ng/mL, with a sensitivity of 73%, specificity of 63%, positive predictive value of 81%, and accuracy of 66.7%. For disease stage N, a cutoff value of 16.5 ng/mL was used. In this sample, the CEA test showed that the sensitivity and specificity for identifying patients with positive N disease were 41% and 89%, respectively, with a positive predictive value of 70% and an accuracy of 59.7%. Carcinoembryonic antigen levels significantly decreased after neoadjuvant therapy in patients with middle and low rectal cancer. Pretreatment CEA levels were primarily associated with tumor invasion depth.