Imatinib induces durable hematologic and cytogenetic responses in patients with accelerated phase chronic myeloid leukemia: results of a phase 2 study

Moshe Talpaz, Richard T. Silver, Brian J. Druker, John M. Goldman, Carlo Gambacorti-Passerini, Francois Guilhot, Charles A. Schiffer, Thomas Fischer, Michael W.N. Deininger, Anne L. Lennard, Andreas Hochhaus, Oliver G. Ottmann, Alois Gratwohl, Michele Baccarani, Richard Stone, Sante Tura, Francois-Xavier Mahon, Sofia Fernandes-Reese, Insa Gathmann, Renaud Capdeville, Hagop M. Kantarjian, Charles L. Sawyers

Chronic myelogenous leukemia (CML) is caused by expression of the BCR-ABL tyrosine kinase oncogene, the product of the t(9;22) Philadelphia translocation. Patients with CML in accelerated phase have rapidly progressive disease and are characteristically unresponsive to existing therapies. Imatinib (formerly STI571) is a rationally developed, orally administered inhibitor of the Bcr-Abl kinase. A total of 235 CML patients were enrolled in this study, of whom 181 had a confirmed diagnosis of accelerated phase. Patients were treated with imatinib at 400 or 600 mg/d and were evaluated for hematologic and cytogenetic response, time to progression, survival, and toxicity. Imatinib induced hematologic response in 82% of patients and sustained hematologic responses lasting at least 4 weeks in 69% (complete in 34%). The rate of major cytogenetic response was 24% (complete in 17%). Estimated 12-month progression-free and overall survival rates were 59% and 74%, respectively. Nonhematologic toxicity was usually mild or moderate, and hematologic toxicity was manageable. In comparison to 400 mg, imatinib doses of 600 mg/d led to more cytogenetic responses (28% compared to 16%), longer duration of response (79% compared to 57% at 12 months), time to disease progression (67% compared to 44% at 12 months), and overall survival (78% compared to 65% at 12 months), with no clinically relevant increase in toxicity. Orally administered imatinib is an effective and well-tolerated treatment for patients with CML in accelerated phase. A daily dose of 600 mg is more effective than 400 mg, with similar toxicity.