The FOLICOLOR trial aims to evaluate whether a liquid biopsy-guided follow-up strategy can improve outcomes in patients with unresectable, metastatic colorectal cancer (mCRC) receiving first-line systemic treatment. The approach uses NPY methylation-based circulating tumor DNA (ctDNA) analysis from blood samples to monitor treatment response and guide clinical decision-making. Eligible patients are adults diagnosed with unresectable, metastatic colorectal cancer who are starting first-line treatment. The primary goal is to demonstrate a clinically meaningful benefit, particularly in terms of quality of life (QoL) and reduction of treatment-related toxicity, by allowing earlier and more personalized therapeutic adjustments based on liquid biopsy findings.