A meta-analysis comparing the clinical validity of carcinoembryonic antigen (CEA)-based analysis, MRD testing, PET, and CT for recurrence surveillance for colorectal cancer showed that sensitivity (CEA: 52%; MRD testing: 68%; PET: 95%; and CT: 77%) was the highest for PET, whereas specificity (CEA, 88%; MRD testing, 95%; PET, 87%; CT, 84%) and positive predictive value (CEA: 4.13, MRD testing: 12.83, PET: 7.15, CT: 4.78) were the highest for MRD testing [100]. Here, CEACAM5 is linked to colorectal cancer.