Treatment outcome in a population-based, ‘real-world’ cohort of patients with chronic myeloid leukemia

Evaluations of the ‘real-world’ efficacy and safety of tyrosine kinase inhibitors in patients with chronic myeloid leukemia are scarce. A nationwide, population-based, chronic myeloid leukemia registry was analyzed to evaluate (deep) response rates to first and subsequent treatment lines and eligibility for a treatment cessation attempt in adults diagnosed between January 2008 and April 2013 in the Netherlands. The registry covered 457 patients; 434 in chronic phase (95%) and 15 (3%) in advanced disease phase. Seventy-five percent of the patients in chronic phase were treated with imatinib and 25% with a second-generation tyrosine kinase inhibitor. At 3 years 44% of patients had discontinued their first-line treatment, mainly due to intolerance (21%) or treatment failure (19%). At 18 months 73% of patients had achieved a complete cytogenetic response and 63% a major molecular response. Deep molecular responses (MR^4.0 and MR^4.5) were achieved in 69% and 56% of patients, respectively, at 48 months. All response milestones were achieved faster in patients treated upfront with a second-generation tyrosine kinase inhibitor, but ultimately patients initially treated with imatinib also reached similar levels of responses. The 6-year cumulative incidence of eligibility for a tyrosine kinase cessation attempt, according to EURO-SKI criteria, was 31%. Our findings show that in a ‘real-world’ setting the long-term outcome of patients treated with tyrosine kinase inhibitors is excellent and the conditions for an attempt to stop tyrosine kinase inhibitor therapy are met by a third of the patients.