ctDNA Methylation Application in Postoperative Relapse and Adjuvant Chemotherapy Efficacy Evaluation

This study is evaluating whether a blood test that detects tiny fragments of tumor DNA (called ctDNA) can identify which colorectal cancer patients are at highest risk of relapse after surgery, and whether that information should guide decisions about giving additional chemotherapy after the operation. **You may be eligible if:** - You are 18 years or older - You have been diagnosed with stage I or II colorectal cancer (without high-risk features) - You are scheduled for surgery to remove the cancer - Your ctDNA blood test is positive before surgery (indicating cancer DNA is detectable in your blood) - Your general health is good (ECOG score 0–1) **You may NOT be eligible if:** - You have a personal history of colorectal cancer or adenomas (pre-cancerous polyps) - You received chemotherapy before surgery - You are pregnant or breastfeeding - You have another active cancer Talk to your doctor to see if this trial is right for you.