A Prospective Multicentre Clinical Study of Dynamic Monitoring of Plasma ctDNA Methylation Markers to Predict Recurrence of Colorectal Cancer After Complete Resection of Peritoneal Metastases

The goal of this clinical trial is to explore the predictive effect of postoperative plasma ctDNA methylation status on postoperative recurrence free survival (RFS) of colorectal cancer patients with peritoneal metastasis after R0/R1 resection. The main questions it aims to answer are: Preoperative and postoperative plasma ctDNA methylation detection (ColonAiQ) was performed in patients with peritoneal metastasis from colorectal cancer who underwent R0/R1 resection. Clinical information of patients was collected to explore the predictive effect of postoperative plasma ctDNA methylation status on postoperative recurrence free survival (RFS) of colorectal cancer patients with peritoneal metastasis. Participants will: The patients were followed up according to the normal review procedure of the hospital and the NCCN guidelines until at least 24 months after surgery. The review content included CT/MRI imaging evaluation and blood CEA (every 3 months). Whole-blood samples were obtained for timely plasma separation and ctDNA extraction at 1 month after surgery (before the start of postoperative chemotherapy) and every 3 months through 24 months after surgery. One blood sample was obtained when tumor recurrence was first detected on imaging. Detection of methylation in tissue and plasma samples 1. GutSeer methylation NGS was performed on peritoneal metastatic cancer tissues and paired normal peritoneal tissues. 2. ctDNA GutSeer methylation NGS was performed on plasma samples before surgery, 1 month after surgery, 24 months after surgery, and when tumor recurrence was first detected by imaging examination. 3. ctDNA methylation PCR (ColonAiQ) was performed on plasma samples before surgery, 1 month after surgery, every 3 months to 24 months after surgery, and when tumor recurrence was first detected by imaging examination.