A Randomized Controlled Trial of Plasma ctDNA Methylation-Guided Adjuvant Chemotherapy Decision-Making in High-Risk Stage III (T4N+ or T1-3N2) Colorectal Cancer

Patients with T4N+ or T1-3N2 disease will be randomly assigned to either the control group (FOLFOX/CAPOX for 6 months) or the intervention group (FOLFOX/CAPOX plus bevacizumab for 6 months) to receive adjuvant therapy. Venous blood samples (8-16 mL) will be collected at 1 month, 3 months, and 6 months postoperatively for dynamic monitoring of plasma ctDNA.

Inclusion criteria

• Age ≥18 years, regardless of sex;
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-2, with an expected survival of >3 months;
• Histologically confirmed postoperative pTNM stage high-risk stage II colorectal cancer;
• Positive ctDNA status at 1 month after surgery;
• Expected survival of >12 months;
• Ability to understand and willingness to sign a written informed consent form (personally or via a legally authorized representative/guardian), indicating that the subject understands the study objectives and required procedures and agrees to participate.

Exclusion criteria

• Receipt of neoadjuvant therapy prior to surgery;
• Blood transfusion during surgery or within 2 weeks prior to surgery;
• Pregnant or breastfeeding women, or individuals of reproductive potential who are not using adequate contraception;
• History of other malignancies within the past 5 years, except for adequately treated carcinoma in situ of the cervix or non-melanoma skin cancer;
• Uncontrolled primary brain tumors or central nervous system metastases, or presence of significant intracranial hypertension or neuropsychiatric symptoms;
• Presence of severe or uncontrolled comorbidities, including but not limited to:Severe cardiac disease that remains unstable despite treatment, including myocardial infarction, congestive heart failure, unstable angina, symptomatic pericardial effusion, or unstable arrhythmia within 6 months prior to enrollment; Clearly diagnosed neurological or psychiatric disorders, including dementia or seizure disorders;Severe or uncontrolled infections;Active disseminated intravascular coagulation (DIC) or significant bleeding tendency;Significant impairment of major organ function;
• Any other condition that, in the opinion of the investigator, would make the patient unsuitable for participation in this study.