Successful treatment with nilotinib after imatinib failure in a CML patient with a four-way Ph chromosome translocation and point mutations in BCR/ABL gene.

Chronic myelogenous leukemia (CML) is characterized by Philadelphia (Ph) chromosome with a chimeric gene BCR-ABL created by reciprocal t(9:22) (q34;q11) translocation. Variant Ph chromosome translocations involving chromosomes other than 9 and 22 are found in 5-10% of CML cases. We here report a CML patient who carries a four-way Ph chromosome translocation, t(9;22;15;19) (q34;q11;q15;q13). The patient was diagnosed in 1997 and initially treated with hydroxyurea. In 2002, treatment with imatinib, a selective BCR-ABL tyrosine kinase inhibitor (TKI), was started but Ph-positive chromosomes remained at the levels of 42-65%, indicating imatinib failure. In 2006, the point mutations of F359I and L387M were detected in BCR/ABL gene, which may be related to imatinib failure. Treatment with nilotinib, a TKI with high target specificity, was then started which resulted in durable major molecular response. Administration of nilotinib offered an effective treatment in a CML patient with variant Ph chromosome translocations and BCR-ABL point mutations after imatinib failure.