Diagnosis and Monitoring of Colorectal Cancer by L6 Blood Serum Polymerase Chain Reaction Is Superior to Carcinoembryonic Antigen-Enzyme-Linked Immunosorbent Assay

PURPOSE: The aim of this study was to compare carcinoembryonic antigen levels with detection of messenger ribonucleic acid coding for the tumor-associated antigen L6 in patients with colorectal cancer. Not only are carcinoembryonic antigens expressed by the corresponding tumor cell, but the messenger ribonucleic acid of tumor-associated antigens, in contrast, is produced exclusively by viable tumor cells. METHODS: L6 messenger ribonucleic acid was determined by reverse-transcription polymerase chain reaction. Carcinoembryonic antigen was measured by the enzyme-linked immunosorbent assay technique, with a cutoff value of 40 microg/l. Blood serum was sampled from 187 patients with colorectal cancer. Statistical significance was calculated with the McNemar chi-squared test. RESULTS: Preoperatively, 79 percent of patients in all stages were positive for L6 messenger ribonucleic acid, whereas only 35 percent had elevated carcinoembryonic antigen titers (P < 0.001). In Dukes A tumors, 84.9 percent of patients were positive for L6 messenger ribonucleic acid, whereas carcinoembryonic antigen was elevated in only 16.9 percent of patients. Only in Dukes D tumors did the enzyme-linked immunosorbent assay for carcinoembryonic antigen exhibit the same sensitivity as reverse-transcription polymerase chain reaction for L6 messenger ribonucleic acid. Recurrence was detected significantly earlier by reverse-transcription polymerase chain reaction for L6 messenger ribonucleic acid than by enzyme-linked immunosorbent assay for carcinoembryonic antigen. CONCLUSION: L6 is more sensitive and precise than carcinoembryonic antigen in diagnosing and monitoring colorectal cancer.