Circulating Tumor DNA Methylation Guiding Postoperative Adjuvant Chemotherapy in Stage III Colorectal Cancer

The goal of this randomized controlled trial is to investigate whether ctDNA methylation is a more precise indicator to guide postoperative adjuvant chemotherapy in stage Ill colorectal cancer. The main questions it aims to answer are: 1. Whether ctDNA methylation-guided escalation strategy is superior to standard treatment for stage III high-risk CRC patients. 2. Whether ctDNA methylation-guided de-escalation strategy is non-inferior to standard treatment for stage III low-risk CRC patients. 325 cases were included in the high-risk cohort (T4 and/or N2) and 665 cases were included in the low-risk cohort (T1-T3, N1). Then patients in each cohort were randomly assigned to ctDNA-guided treatment (ctDNA-guided group) and standard treatment (standard treatment group) in a ratio of 2:1. The standard treatment group and ctDNA-negative group in the high-risk cohort were treated with XELOX regimen for 6 months, and the ctDNA-positive group in the high-risk cohort was treated with cmFOLFOXIRI regimen for 6 months. The standard treatment group and the ctDNA-positive group in the low-risk cohort were treated with XELOX regimen for 3 months, while the ctDNA-negative group in the low-risk cohort did not receive adjuvant chemotherapy.