Increased proportion of mature NK cells is associated with successful imatinib discontinuation in chronic myeloid leukemia
The study analyzed function and phenotype of T and NK cells in relation to successful tyrosine kinase inhibitor cessation in patients with chronic myeloid leukemia. The study was conducted by the Nordic CML study group as a substudy to EURO-SKI clinical trial.
132 adult patients with CML who were treated with imatinib / dasatinib / nilotinib for at least 3 years and sustained deep molecular response for at least 1 year were included. Patients then had monthly RQ-PCR tests to monitor for loss of major molecular response. Blood samples were drawn before stopping TKI, 1 month and 6 months after and analysed by flow cytometry for basic NK, B and T cell counts and proportions. Additional NK and T cell function and immune phenotype were also studied in 45 patients.
Analysis found that having higher proportion of NK cells at time of imatinib discontinuation was associated with increased molecular relapse-free survival (73% vs 51% at 6 months, hazard ratio 2.17, P=0.02). NK cell phenotype in non-relapsing patients have higher proportion of mature NK cells then early relapsing group.
The study only included adult patients, and results from patients on imatinib were presented only (due to small number for dasatinib and nilotinib). Findings may not be directly applicable to pediatric patients with CML.