The long-term durability of cytogenetic response in patients with accelerated phase chronic myeloid leukemia treated with imatinib 600 mg: the GIMEMA CML Working Party experience after a 7-year follow-up

BACKGROUND: Imatinib mesylate is the first line treatment for chronic myeloid leukemia. The advent of imatinib increased survival significantly in patients in an advanced phase of the disease. However, few long-term data on the outcome of these patients based on large, prospective and controlled trials are available. DESIGN AND METHODS: A phase 2 multicenter trial of the use of imatinib 600 mg/daily in patients with accelerated phase chronic myeloid leukemia was sponsored and promoted by the Italian Cooperative Study Group on Chronic Myeloid Leukemia in 2001. RESULTS: One hundred and eleven patients were enrolled; the median follow-up of the 41 living patients is 82 months (range, 73-87). One hundred and seven patients (96%) returned to chronic phase and 79 patients (71%) achieved a complete hematologic response. Cumulative best rates of major cytogenetic response and complete cytogenetic response were 30% and 21%, respectively. All responses were maintained for a minimum of 4 weeks. At last follow-up, four patients were alive in complete remission after allogeneic transplant, 16 patients (14%) had switched to a second generation tyrosine kinase inhibitor and 21 patients (19%) were alive on imatinib therapy. No late toxicities were observed. Progression-free survival and event-free survival rates were 36.5% and 15%, respectively, at 7 years. The median survival time was 37 months, and was significantly associated with the achievement of a complete hematologic response or a complete cytogenetic response. CONCLUSIONS: Imatinib may induce durable responses, associated with prolonged survival, in patients with accelerated phase chronic myeloid leukemia.