Researchers involved in the multicenter U.S. RIGHT trial have reported that Gleevec® (imatinib) 400 mg twice per day is more effective than the standard 400 mg/day for the treatment of newly diagnosed patients with chronic myeloid leukemia (CML) in chronic phase (CP). The details of this study were published in the Journal of Clinical Oncology early online on August 31, 2009.[1]
Standard treatment for CP-CML includes treatment with Gleevec at a dose of 400 mg/day. However, several studies have suggested that dose increases up to 800 mg/day may improve molecular response rates. Researchers from Australia have reported that patients with CP-CML who receive 600 mg/day of Gleevec in the first year of treatment experience improved molecular response rates compared with 400 mg/d.
The current study evaluated Gleevec 400 mg/twice per day in 115 patients with newly diagnosed CML in CP. The completion rate for the study was 72%, with 9% discontinuing Gleevec because of toxicity and 5% discontinuing Gleevec because of unsatisfactory therapeutic results. In this study 79% of patients received at least 90% of the planned dose intensity.
Forty-eight percent of patients achieved a major molecular response (MMR) within six months, 54% by 12 months, and 63% by 18 months. A complete molecular response was achieved within six months in 39%, within 12 months in 44%, and within 18 months in 55%.
These authors compared responses in the current study of Gleevec 800 mg/day with the results of the IRIS study and single-center studies of 400 mg/day. They suggested that the higher dose of Gleevec increased the 12-month major cytogenetic response from 84% to 90%, the 12-month complete cytogenetic response rate from 65% to 85%, and increased the major molecular response rate from 74% to 90%.
Comments: These data suggest that early exposure to higher doses of Gleevec were more effective than lower doses without a significant increase in toxicity. However, many patients appear to do reasonably well with the lower dose of Gleevec, and it remains to be seen what the ultimate standard approach will be in the absence of a large randomized trial comparing different doses.
Reference:
[1] Cortes JE, Kantargian HM, Goldberg SL, et al. High-dose imatinib in newly diagnosed chronic-phase chronic myeloid leukemia: High rates of rapid cytogenetic and molecular responses. Journal of Clinical Oncology [early online publication]. on August 31, 2009.
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