Sorafenib and regorafenib are tyrosine kinase inhibitors that are used in the treatment of hepatocellular carcinoma and which have similar chemical structures and toxicity profiles. We herein report a case in which regorafenib treatment could be continued for 10 months and stable disease could be maintained for a long period despite the discontinuation of sorafenib due to grade 4 liver injury and grade 3 fever. The severe adverse events could be attributed to drug hypersensitivity, since a drug-induced lymphocyte stimulation test (DLST) indicated sensitivity to sorafenib. A DLST for regorafenib was negative. This is the first report showing that regorafenib could be safely administered after the discontinuation of sorafenib due to hypersensitivity.
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