Researchers affiliated with the START-R randomized trial have reported that Sprycel® (dasatinib) is more effective than escalated doses of Gleevec® (imatinib) in patients resistant to Gleevec. The details of this study were published early online in Cancer on June 17, 2009.[1]
Sprycel is reported to be 325-fold more active than Gleevec for inhibition of Bcr-Abl. At the 2006 meeting of the American Society of Hematology, preliminary results of the START-R trial were presented. This study now has a minimum two-year follow-up, which is the subject of the current report.
Patients with CML are usually treated with 400 or 600 mg of Gleevec daily. However, there is emerging data to suggest that the optimal dose of initial treatment is 800 mg/day. In the START-R study, patients with CP of CML resistant to 400 mg or 600 mg of Gleevec were randomly allocated on a 2:1 basis to receive Sprycel or 800 mg of Gleevec. With a minimum two-year follow-up, these authors made the following observations:
- Complete hematologic response was 93% for patients in the Sprycel group and 82% for patients in the high-dose Gleevec group.
- A major cytogenetic response was observed in 53% of patients in the Sprycel group compared with 33% in the high-dose Gleevec group. This response was maintained in 90% of patients in the Sprycel arm and 74% of patients in the high-dose Gleevec arm.
- A complete cytogenetic response was observed in 44% of patients in the Sprycel group and 18% of patients in the high-dose Gleevec group.
- A major molecular response was observed in 29% of patients in the Sprycel group and 12% of patients in the high-dose Gleevec arm.
These authors conclude: “After 2 years of follow-up, dasatinib demonstrated durable response and improved response and progression-free survival rates relative to high-dose imatinib.”
Comments: These data suggest that Gleevec failures should be treated with Sprycel. A recent study further suggests that Sprycel should be instituted as soon as a loss of response following Gleevec is detected. This study also suggests that patients who fail to have an initial major cytogenetic response to Gleevec should be treated with Sprycel.
Reference:
[1] Kantarjian H, Pasquini R, Levy V, et al. Dasatinib or high-dose imatinib for chronic-phase chroniic myeloid leukemia resistant to imatinib at a dose of 400-600 miligrams daily. Cancer [early online publication]. June 17, 2009.
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