Imatinib Mesylate Therapy Improves Survival in Patients with Newly Diagnosed Philadelphia Chromosome-Positive Chronic Myelogenous Leukemia in the Chronic Phase: Comparison with Historic Data

BACKGROUND. The International Randomized study of Interferon-alpha plus cytarabine (IFN-α plus ara-C) versus STI571 (imatinib mesylate) [IRIS trial] in patients with newly diagnosed Philadelphia chromosome (Ph)-positive, chronic-phase chronic myelogenous leukemia (CML) has not shown (to date) a survival advantage for imatinib. This was most likely because approximately 90% of patients receiving IFN-α plus ara-C changed to imatinib therapy after a median of 8 months into therapy. METHODS. The authors analyzed the results with imatinib therapy in patients with newly diagnosed Ph-positive CML in chronic phase and compared their outcome with patients who received IFN-α regimens. A total of 187 patients with Ph-positive CML in early chronic phase treated with imatinib were compared with a historic group of 650 similar patients treated with IFN-α regimens from 1982 until 1997, RESULTS. Patients who received imatinib were significantly older and had significantly more bone marrow basophilia and less leukocytosis. The complete cytogenetic response (Ph 0%) rates were better with imatinib (81% vs. 32%; P < 0.001), as were the survival rates (30-month estimated survival rates 98% vs, 88%; P = 0.01). A multivariate analysis of the total study group of 837 patients identified imatinib therapy to be a significant independent favorable prognostic factor for survival (P = 0.01). CONCLUSIONS. The current study is the first to indicate the survival advantage of imatinib compared with IFN-α, the previous standard of care, in patients with early chronic-phase CML.