Approximately half of all patients diagnosed with locoregional stage II high-risk/stage III colon cancer (LRCC) relapse within two years from the time of curative surgery because of imaging-undetectable micro-metastatic residual disease (MMRD). Given the lack of reliable predictors of individual risk, LRCC patients are treated with one-fits-all adjuvant chemotherapy. This gunshot approach results in either over- or under-treatment. SAGITTARIUS aims to optimize the clinical management of LRCC patients by leveraging circulating tumor DNA (ctDNA) measurement in the patient’s bloodstream to diagnose MMRD and genomic landscape characterization of the patient’s tumors to personalize treatments. SAGITTARIUS is a pragmatic trial whereby real-world patients are treated in two parallel trials based on their MMRD status and the genomic landscape of their tumors. ctDNA-positive patients are randomized to conventional or personalized targeted therapy. ctDNA-negative patients are randomized to either a physician-choice path or Wait&See strategy. Sagittarius will allow for treatment to be better matched against the tumor biology, also allowing for better monitoring – via ctDNA – to assess disease evolution in each patient, minimizing harm and maximizing the odds of cure. The efficacy and effectiveness of this potentially ground-breaking new strategy of care will be measured via multiple outcomes, including safety and time-to-event variables, patient-reported outcome measures, and health-economics evaluation.