Carcinoembryonic antigen (CEA) and the carcinoma antigen 19-9 (CA 19-9) together in early diagnosis of Stage I-II colorectal adenocarcinoma. A case-control study

Background: Colorectal cancer (CRC) is one of the most common cancer worldwide. It causes approximately 50,000 and 95,000 deaths each years in the USA and European Union, respectively. As with all forms of cancers, the early diagnosis of CRC improves patient outcomes and survival. Colonoscopy is the most widely used diagnostic test for this purpose, and a number of tumor markers have been proposed for selecting at-risk patients. Carcinoembryonic antigen (CEA) and the carcinoma antigen 19-9 (CA 19-9) are common serum tumor markers useful in patients with CRC. They are usually considered as having low sensitivity and good specificity in detecting CRC. However, the results vary widely, due to several confounding variables. The aim of this study was to verify the usefulness of serum CEA and CA 19.9 measurement in a homogenous group of patients with CRC. Methods: Ninety-seven patient (67 men, 30 women, and median age 60, range 50-79 years) with histologically confirmed Stage I-II (Dukes A-B) colorectal adenocarcinoma (cases) were enrolled in the study. Controls were 82 sex- and age-matched symptomatic subjects scheduled for screening colonoscopy and benign (non-IBD) colorectal diseases. Current smokers and patients who were alcohol or drugs abusers were excluded from the study, as well those who had previous cancer or chronic diseases requiring lifelong therapies potentially interfering with the results. CEA and CA 19-9 serum levels were measured using commercially available immunoassays, according to the manufacturer’s instructions. CEA by automated homogeneous chemiluminescent immunoassay (luminescent oxygen channeling immunoassay-LOCI), that uses a dyoxetan derivative as luminescence substrate, CA 19-9 by a sandwich assays based on the streptavidin-biotin technology (ELISA). The limit of detection and quantification of the assays employed was 0.2 and 0.5 ng/mL (CEA), and 1.0 and 1.5 KU/mL (CA 19-9) while the reference ranges were 0-5 ng/mL and 1-34 kU/L, respectively. Written informed consent was obtained from all the participants. Results: The results are reported in the Table. The sensitivity of CEA and CA 19-9 was similar (p=0.74) and did not improve significantly when they were used together (p=0.13). The combination of both markers showed an accuracy higher than that of both CEA and CA 19-9 (66.5% vs. 44.7%-59.2%, p=0.02). Conclusion: Unfortunately, serum tumor markers CEA and CA 19-9 measurement has low sensitivity and accuracy, ranging approximately between 28%-40% and 45%-66%, respectively. However, due to their high specificity (up to 98%) it should be suggested in selecting patients for further CRC screening evaluation.