This is a prospective, multicenter, observational, real-world study. Research objects: patients with surgically resectable colorectal cancer and ctDNA positive before surgery in stage I and stage II (without high risk). After giving fully informed consent, the participants will undergo the regular treatment according to NCCN guidelines. Serial analysis of ctDNA will be performed at specific time points including pre-treatment, postoperative week 3, postoperative 5 years ( every 3 months for the first 2 years, and every 6 months for the rest 3 years). Participants will be observed and examined during the follow-up period.
In this study, the investigators aimed to apply their previously developed multi-locus blood-based assay targeting circulating tumor DNA methylation to monitor postoperative relapse and evaluate adjuvant chemotherapy efficacy in resected stage I and stage II (without high risk) colorectal cancer after radical resection.