Middelharnis

Researchers are studying patients with non-metastatic stage II colon cancer who are part of the Dutch ColoRectal Cancer cohort PLCRC and who consented to additional blood samples. The study aims to evaluate how many patients with detectable circulating tumor DNA ctDNA after surgery begin adjuvant chemotherapy. This observational and interventional trial includes patients who do not have a standard indication for chemotherapy and involves a randomized design to compare ctDNA-guided treatment with standard care. Patients are randomly assigned to one of two groups the ctDNA-based treatment group or the standard care group. In the ctDNA group, blood samples taken after surgery are analyzed for ctDNA. Those with detectable ctDNA are offered 3 months of adjuvant chemotherapy using CAPOX a combination of fluoropyrimidine and oxaliplatin. Patients without detectable ctDNA receive routine follow-up care. The standard care group receives routine follow-up without knowledge of their ctDNA results. Participants will have blood collected before surgery, after surgery, and during follow-up. Researchers will monitor who starts chemotherapy within 8 to 12 weeks after surgery and will track recurrence rates, disease-free survival, overall survival, time to recurrence, quality of life, and cost-effectiveness over several years. Follow-up assessments occur up to 10 years, allowing detailed long-term evaluation of treatment impact and patient outcomes.