LAUSR

651Background: Regorafenib is an oral multi kinase inhibitor with clinical activity in colorectal cancer, gastrointestinal stromal tumors and hepatocellular cancer. Drug- drug interactions are commonly encountered in clinical practice and warfarin continues to be the most commonly prescribed anticoagulant among cancer patients in the clinic. The interaction of regorafenib with warfarin has not been studied. Methods: Patients at a single institution being prescribed regorafenib were identified and charts reviewed for concurrent warfarin therapy. Baseline characteristics, indications for regorafenib and warfarin therapy was determined. Patients were followed up to the first 8 weeks of combination therapy. Results: We identified 6 patients on concurrent regorafenib and warfarin. All patients had refractory colon cancer. Median age was 74, 4 were male and 5 white. Indication for warfarin was venous thromboembolism in 5 and atrial fibrillation in 1. Baseline INR ranged from 1.1 to 2.4. An increase in INR was s...