Imatinib mesylate therapy of chronic phase chronic myeloid leukemia resistant or intolerant to interferon: results and prognostic factors for response and progression-free survival in 150 patients.

ABSTRACT

BACKGROUND AND OBJECTIVES: Imatinib mesylate has recently been shown to be highly effective in chronic-phase chronic myeloid leukemia (CML). The results of imatinib treatment in chronic-phase CML patients resistant or intolerant to interferon (IFN) and the factors predicting therapeutic response and progression-free survival were analyzed. DESIGN AND METHODS: One hundred and fifty patients with chronic-phase CML resistant (n=111) or intolerant (n=39) to IFN were treated with imatinib. Prognostic factors for response and disease progression were assessed by multivariate analysis. RESULTS: The median time from diagnosis was 43 months (0.5-188), median IFN therapy 21.5 months (0.5-140) and median follow-up from starting imatinib 13.6 months (range 3-23). Complete hematologic response was achieved in 96 of 97 patients. Complete, partial and minor cytogenetic responses were present in 44%, 22%, and 8% of patients at 12 months. Grade III-IV neutropenia, thrombocytopenia, and anemia developed in 33%, 16%, and 6% of patients, respectively. Sixty-five patients discontinued treatment for a median of 4 weeks (1-36) due to toxicity. The rate of progression-free survival (lack of accelerated/blastic phase with persistent response) was 89.2% (95% CI 84-94.4) at 12 months and 80.2% (95% CI 72.2-88.2) at 18 months. Platelets > 450x10(9)/L and treatment discontinuation > 4 weeks were associated with a lower rate of major (complete plus partial) cytogenetic response. Patients in Sokal's high-risk group and those who did not achieve a major cytogenetic response had significantly shorter progression-free survival. INTERPRETATION AND CONCLUSIONS: Imatinib is highly effective in chronic-phase CML patients resistant or intolerant to IFN, especially in those with normal platelet counts and in those not requiring prolonged treatment discontinuation due to neutropenia.