This study will utilize ctDNA methylation detection to evaluate patients with high-risk T3N0 stage II colorectal cancer who are ctDNA-positive one month after surgery. It aims to investigate the impact of different adjuvant chemotherapy regimens on ctDNA clearance rates and their prognostic significance. By using postoperative ctDNA status to identify patients at high risk of recurrence, the study seeks to implement intensified chemotherapy strategies (treatment escalation) at an early stage, thereby improving ctDNA clearance and ultimately enhancing patient outcomes