Circulating Tumor DNA Methylation Guided Postoperative Adjuvant Chemotherapy for High-risk Stage II/III 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. Evidence suggests that Stage III CRC patients can benefit from standard adjuvant chemotherapy. It is worth noting that some high-risk stage II patients, especially those with T4N0, have a poorer prognosis compared to stage IIIA (T1-2N+). Adjuvant chemotherapy is now also recommended for postoperative cases of high-risk stage II CRC. Given the high effectiveness of the three-drug FOLFOXIRI regimen in treating metastatic CRC and the success of adjuvant chemotherapy in treating pancreatic cancer, the combination of 5-fluorouracil, oxaliplatin, and irinotecan may have a synergistic effect. Extensive study results have shown that: (a) The status of ctDNA methylation after surgery is significantly correlated with patient prognosis, and patients who are positive for ctDNA methylation in the first 1-4 weeks after surgery (before adjuvant chemotherapy) have a poor prognosis. (b) Patients who are ctDNA methylation positive in the first 1-4 weeks after surgery (before adjuvant chemotherapy) can benefit from adjuvant chemotherapy, and achieving ctDNA methylation negativity through adjuvant chemotherapy significantly improves patient prognosis. This project focuses on exploring the optimized mode of postoperative adjuvant chemotherapy for high-risk stage II and III CRC guided by ctDNA methylation, which has high scientific and innovative value. 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 0.05%. This study will use this ctDNA methylation detection technology to perform quantitative detection of ctDNA methylation in the plasma of enrolled patients, and explore the effect of different chemotherapy regimens on ctDNA clearance rate and the prognostic value for ctDNA positive patients. We hope to screen out high-risk populations for recurrence through postoperative ctDNA testing, and administer more intensive chemotherapy regimens (chemotherapy upgrading) as early as possible to improve ctDNA clearance rate and patient prognosis.