CEACAM5 and colorectal cancer: Conventional circulating biomarkers, such as carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9, do not fully satisfy the clinical requirements for monitoring colorectal cancer (CRC) tumor burden in clinical practice because of their moderate levels of sensitivity and specificity.7 Therefore, we used circulating tumor DNA (ctDNA) analysis to assess the patients’ tumor burden.