Predictive Value of ctDNA for NED Status in mCRC and Its Utility in Guiding Therapeutic Intervention

The goal of this clinical trial is to detect the prognostic value of longitudinal monitoring circulating tumor DNA (ctDNA) for no evidence of disease (NED) status in metastatic colorectal cancer (mCRC) patients and its utility in guiding therapeutic intervention. The main questions it aims to answer are: 1. Whether ctDNA monitoring could evaluate NED status ahead of normal radiologic monitoring. What about the concordance of evaluating NED status by ctDNA monitoring compared with normal radiologic monitoring? 2. Whether the patients with ctDNA positive status could benefit from early therapeutic intervention. Patients who receive any kinds of therapies with the aim of NED and are confirmed by clinical and radiologic examination will go through longitudinal ctDNA monitoring. According to the results of ctDNA monitoring, the patients will be divided into ctDNA positive group and ctDNA negative group. Patients in ctDNA positive group will receive individual therapeutic plan decided by the investigator. Patients in ctDNA negative group will receive regular examinations. When radiologic recurrences are confirmed, the patients will be re-evaluated for a second opportunity of radical resection.