Our study examined the cost-effectiveness of the ivosidenib regimen based on findings from the ClarIDHy phase III trial among patients with advanced ICC and the IDH1-mutant compared with that of mFOLFOX (as per the NCCN and ESMO guidelines) and 5-FU/LV (the only reimbursed regimen by the Taiwan NHI for ICC with IDH1 mutations). Here, IDH1 is linked to intrahepatic cholangiocarcinoma.