A case of metastatic colon cancer with RAS wild tumor progressed during the treatment with mFOLFOX6 plus panitumumab

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We herein report a case of metastatic colon cancer RAS wild tumor progressed during the treatment with FOLFOX + panitumumab and then recognized as BRAF mutation and MSI-H. Seventy eight years-old male patient showed anastomotic recurrence of colon cancer after curative resection of Stage II ascending colon cancer six years before the appearance of the recurrence. Six months after R0 resection, surveillance CT was performed and diagnosed as recurrent tumor invaded to duodenum. For R0 resection, mFOLFOX6 plus panitumumab therapy was initiated to expect early tumor shrinkage because of RAS wild tumor. However, tumor progressed after 4 cycles. The second-line therapy was not able to started because the disease progression was extremely rapid. He died 4 months after initiation of therapy. BRAF mutation and MSI-H were recognized from his tumor by the additional analyses.