Circulating Tumor DNA Methylation Guided Postoperative Follow-up Strategy for Non-metastatic Colorectal Cancer

Colorectal cancer (CRC) is one of the most common gastrointestinal tumors. According to the latest cancer report, the incidence and mortality rates of CRC are both ranked top 5 among malignant tumors worldwide and continue to rise. Patients who receive treatment in the early stage (stage I) have a 5-year survival rate of approximately 90%. However, for high-risk stage II and III colorectal cancer patients, the 5-year survival rate is only 40%-70%, and almost half of the patients experience postoperative recurrence and metastasis. Circulating tumor DNA (ctDNA) is a small fraction of total cell-free DNA (cfDNA) in peripheral blood circulation, carrying tumor-specific genetic and epigenetic information. It can usually be detected in the serum or plasma of tumor patients in peripheral blood. Studies have shown that methylation detection of plasma ctDNA can be used for predicting the efficacy and prognosis of tumor postoperatively, as well as for dynamic monitoring. Current methods for monitoring CRC recurrence include testing for carcinoembryonic antigen (CEA) in blood and periodic computed tomography (CT) scans. However, due to the low sensitivity of CEA and the radiation and cost limitations of CT examination, the disease status of postoperative CRC patients cannot be well-monitored. ctDNA is a promising biomarker for monitoring the recurrence and metastasis of CRC. Research results have shown that ctDNA can be detected in nearly all subjects before surgery, and the changes in ctDNA levels are related to the extent of surgical resection. The detection of ctDNA after surgery generally indicates recurrence within one year. ctDNA may be a more reliable and sensitive indicator than the current standard biomarker CEA, providing a window for early intervention. This multicenter, prospective, and randomized controlled cohort study uses a single-tube methylation-specific quantitative PCR (mqMSP) detection, which detects 10 different methylation markers and can quantitatively analyze plasma samples containing tumor DNA as low as 0.01%. This study will use the ctDNA methylation detection technology to conduct quantitative detection of ctDNA methylation in the plasma of enrolled patients, hoping to predict the recurrence and metastasis risk of patients at an earlier stage through ctDNA changes, and to explore the value of ctDNA detection in guiding postoperative follow-up for non-metastatic CRC.