LAUSR

e15134Background: We use a decision analytic model to project the effectiveness and cost burden of microsatellite instability-high (MSI-H)/mismatch repair-deficient (dMMR) metastatic colorectal cancer (mCRC) treatment in the era of immunotherapy. Methods: We simulated the treatment of hypothetical patients with MSI-H/dMMR mCRC in two scenarios: patients refractory to two lines of chemotherapy, or untreated. We compared nivolumab, ipilimumab/nivolumab, trifluridine/tipiracil (third-line) and mFOLFOX6/cetuximab (first-line) based on the CheckMate 142, RECOURSE, and CALGB/SWOG 80405 trials. Results: Ipilimumab/nivolumab was the most effective strategy in both third- and first-line settings, and both checkpoint inhibitor therapies were more effective than chemotherapy (Table 1). However, neither checkpoint inhibitor therapy was cost-effective compared to chemotherapy in the base case due to maintenance nivolumab drug cost. Ipilimumab/nivolumab could be the most cost-effective strategy in both settings if trea...