Four Years of Follow-Up of 1027 Patients with Late Chronic Phase (L-CP), Accelerated Phase (AP), or Blast Crisis (BC) Chronic Myeloid Leukemia (CML) Treated with Imatinib in Three Large Phase II Trials.

Background

This report updates the results of 3 large phase II studies of the orally available BCR-ABL tyrosine kinase inhibitor imatinib for patients (pts) in AP, BC and late chronic phase (L-CP) CML failing prior interferon therapy (Kantarjan et al, ASH 2003; Talpaz et al, ASH 2003).

Methods

Between August 1999 and June 2000, 1027 pts were enrolled in phase II trials for CML in L-CP (n=532), AP (n=235) or BC (n=260). Pts in L-CP were treated with 400 mg/day and pts in AP or BC with either 400 or 600 mg/day. Dose escalation up to 800 mg/d was allowed in the late-chronic phase study. Pts with a confirmed diagnosis of AP (n=181), BC (n=229) and late-chronic phase (n=454) were evaluated for efficacy. All pts were evaluated for safety. The median time from initial diagnosis to study entry was 32 months for L-CP pts.

Results

As of 31-Jul-03, 5% patients with BC, 25% of CML-AP and 64% of L-CP patients still remain on treatment.

At the recommended dose of 600 mg, an estimated 40% (AP) and 7% (BC) of patients remained progression-free at 36 months, and an estimated 55% (AP) and 14% (BC) patients were alive at 36 months after initiation of imatinib. The 3-year survival rates for pts with AP with a major cytogenetic response at 3 months were 85% vs. 52% for pts with no response (p<0.001). In L-CP patients with a median follow-up of 40 months, 65% of patients achieved a major cytogenetic response, which was complete in 52%. The cytogenetic responses were durable with an estimated 82% of the pts in continuos major cytogenetic response at 3 years. The estimated rates of progression-free survival and overall survival at 3 years were 80% and 88%. Pts with at least a minor cytogenetic response at 6 months ≤65% Ph+ cells) had an estimated 3-year survival rate of 96% vs. 86% for pts with a ( minimal response and 81% for pts with no cytogenetic response (p<0.001).

Conclusion

In large phase II studies, continuous imatinib treatment is safe and has improved progression-free survival of patients at all stages of CML. Responses to imatinib are durable and are predictive of long-term outcomes. These results will be further updated at the meeting using a data base lock planned for 20-Sept-04 (using data collected up to 31-July-04, i.e. more than 4 years after the last pts enrollment).