Prognostic significance of early molecular response in chronic myeloid leukemia patients treated with tyrosine kinase inhibitors.

A 55-year-old man presented with splenomegaly (10 cm below left costal margin) and leucocytosis (145 × 10(9)/L). Differential showed neutrophilia with increased basophils (2%), eosinophils (1.5%), and left shift including myeloblasts (3%). A diagnosis of chronic myeloid leukemia in chronic phase was established after marrow cytogenetics demonstrated the Philadelphia chromosome. Molecular studies showed a BCR-ABL1 qPCR result of 65% on the International Scale. Imatinib therapy at 400 mg daily was initiated due to patient preference, with achievement of complete hematological response after 4 weeks of therapy. BCR-ABL1 at 1 and 3 months after starting therapy was 37% and 13%, respectively (all reported on International Scale). Is this considered an adequate molecular response?