For this study, researchers defined disease progression as blood counts no longer being controlled by Gleevec, loss of a cytogenetic response, advancement to accelerated phase or blast crisis, or death during treatment.

Researchers found that achieving a complete cytogenetic response, which refers to the Philadelphia chromosome disappearing altogether from a patient's blood cells, had a significant impact on a patient's long-term outcome regardless of when it occurred in treatment. Patients whose cytogenetic response was complete were least likely to experience disease progression.

Interestingly, the length of treatment needed to reach a complete response had no effect on survival. Survival without disease progression at 24 months was 96 percent for patients with a complete response within the first three to six months, and 93 percent for those who achieved a complete response only after six months.

Researchers also looked at which patients were likely to have a complete response to Gleevec. Patients who were 35 percent Philadelphia chromosome positive or less at any time during treatment often had a complete response. Patients who were greater than 95 percent Philadelphia chromosome positive at three months still had nearly a 50 percent chance of subsequently obtaining a complete response. However, patients who were greater than 95 percent Philadelphia chromosome positive after six months or more of therapy had no more than a 14 percent chance of achieving a complete response.

Thus, three months is too soon to judge a response to Gleevec. On the other hand, patients who are greater than 95 percent Philadelphia chromosome positive at six months may be candidates for other treatment options.

Researchers are further analyzing the data to find out if incre
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Contact: Rachel MacKnight
macknigh@ohsu.edu
503-494-8231
Oregon Health & Science University
6-Dec-2003