Imatinib Mesylate for Refractory Acute Myeloblastic Leukemia Harboring inv(16) and C-KIT Exon 8 Mutation.

While approximately 50% of acute myeloblastic leukemia (AML) patients carrying favorable karyotypes show long-term survival, treatment outcome is not universally favorable in such patients. Recently, mutations in the C-KIT and FLT3 genes were frequently found in patients with inv(16) AML. Of 15 patients we examined, 2 had the FLT3-D835 mutations, 1 had a mutation in the second tyrosine kinase domain, 1 in the juxtamembrane domain, and 1 in the exon 8 of the C-KIT gene. These mutations are potential therapeutic targets for specific tyrosine kinase inhibitors. In this study, we present a case of inv(16) AML harboring C-KIT exon 8 mutation that was successfully treated with imatinib mesylate. After treatment with low-dose cytarabine, aclarubicin and granulocyte colony-stimulating factor (CAG) plus vincristine and prednisone (VP), a 58-year-old man with AML M4Eo showed second relapse with left inguinal lymph nodes involvement. The patient was treated with high-dose cytarabine and mitoxantrone only unsuccessfully. However, the following treatment with 400 mg of imatinib mesylate for 2 weeks in combination with CAG plus VP brought about complete hematological remission. This treatment was well tolerated, and no severe adverse events occurred. This observation suggests that imatinib mesylate can be an alternative treatment modality for AML with the mutation in exon 8 of the C-KIT gene, although further studies are required to confirm the efficacy of this approach for refractory AML.