In this clinical study, ctDNA will be detected in postoperative patients with stage Ⅱ and Ⅲ colorectal cancer to evaluate the correlation between ctDNA and the risk of postoperative recurrence. According to the dynamic changes of ctDNA after adjuvant chemotherapy, the correlation between ctDNA and postoperative DFS will be compared, and the feasibility of ctDNA as a molecular marker to evaluate the risk of postoperative recurrence of colorectal cancer will be investigated.
