Head‐to‐head comparison of the diagnostic value of fecal and serum carcinoembryonic antigen for colorectal cancer detection

This study aimed to conduct a head-to-head comparison of the diagnostic value of serum carcinoembryonic antigen (sCEA) and fecal CEA (fCEA) for colorectal cancer (CRC) detection. Fecal and serum samples from 80 CRC cases at various tumor stages and 100 controls free of colorectal neoplasms at screening colonoscopy were randomly selected from two ongoing large prospective CRC detection studies (IDA and BLITZ) for CEA measurements. Fecal samples were processed using two methods: with and without mechanical homogenization. Diagnostic performance (area under the curve value [AUC], sensitivity) of fCEA and sCEA was compared individually and in combination with fecal immunochemical test (FIT). The fCEA concentrations obtained using both sample processing methods were highly correlated in both CRC cases and controls, but neither correlated with sCEA. The sCEA concentrations demonstrated significantly greater differences between the CRC and control group compared to fCEA concentrations. The diagnostic performance of fCEA obtained with both fecal sample processing methods was significantly lower than that of sCEA (AUC: 0.62 and 0.57 vs. 0.83, both p < .001; sensitivity at 85% specificity: 36.2% and 26.2% vs. 52.5%, p = .067 and .002). Algorithms combining sCEA with fCEA did not significantly improve the diagnostic performance compared to sCEA alone. Combining FIT with sCEA improved diagnostic performance over FIT alone. However, combining FIT with fCEA showed no improvement. In conclusion, fCEA is inferior to sCEA as a non-invasive biomarker for CRC detection. Combination of FIT with sCEA demonstrates greater potential for CRC screening than combination of FIT with fCEA.