Kinase domain mutations of BCR-ABL identified at diagnosis before imatinib-based therapy are associated with progression in patients with high Sokal risk chronic phase chronic myeloid leukemia

Abstract

Acquired resistance to imatinib in the advanced phase of chronic myeloid leukemia (CML) has been associated with mutations in the kinase domain (KD) of BCR-ABL. On the contrary, the prognostic implication of KD mutations in early chronic phase (CP) patients at diagnosis before imatinib-based therapy has not yet been established. We have reviewed the status of mutations in 43 patients with early CP-CML on the samples collected at diagnosis. Mutations were identified by direct sequencing (DS) with BidDye Terminator v 1.1. cycle sequencing kit and analyzed with a 3130 ABI capillary electrophoresis system. Eight out 13 (61.5%) high Sokal risk patients showed the following mutations: Y253C, S265R, E255K, F359Y, N374S, E255V, E255V, E255V. Three patients progressed during imatinib and second-line inhibitors and died of blastic phase CML at 23, 33, and 69 months. Another patient with intermediate Sokal risk showed D363G mutation at diagnosis, progressed under imatinib, was allografted and he is now alive in major molecular remission (MMR). No low-risk patient carried KD mutation at diagnosis. In conclusion, KD mutations conferring high-level imatinib resistance are present in patients with de novo CML and in some of them lead to disease progression.