LOW-DOSES OF INTERFERON-ALPHA ARE AS EFFECTIVE AS HIGHER DOSES IN INDUCING REMISSIONS AND PROLONGING SURVIVAL IN CHRONIC MYELOID-LEUKEMIA

Objective: To determine the toxicity and efficacy of low-dose interferon-alpha therapy in inducing remissions and prolonging survival in patients with chronic myeloid leukemia. Design: Phase II evaluation and comparison with historical control patients and other series in which the investigators used higher interferon-alpha doses. Setting: Tertiary care leukemia research clinic. Patients: 41 patients with newly diagnosed or previously treated chronic-phase, Philadelphia chromosome-positive chronic myeloid leukemia received interferon-alpha at a dose of 2 x 10(6) U/m(2) body surface area daily for 28 days and then three times weekly. Measurements: Complete blood counts and physical examinations were done monthly to determine hematologic remission and toxicity. To determine karyotypic response, bone marrow cytogenetic analyses were done at 6 monthly intervals in patients who achieved a complete hematologic remission. In addition, Kaplan-Meier survival curves and median survival values were generated from diagnosis and the start of therapy with interferon-alpha. Results: 70% of patients treated with low-dose interferon-alpha within 1 year of diagnosis achieved a complete hematologic remission, and 22% of these patients had a major or complete karyotypic response. Investigators who used higher interferon-alpha doses in similar patient populations have reported complete hematologic remission rates of 59% to 70% and major and complete cytogenetic response rates of 16% to 29%. The Kaplan-Meier estimated 5-year survival rate of minimally pretreated patients in our study is 73% (95% Cl, 51% to 95%), which compares favorably with survivals reported by investigators who used higher doses. The estimated yearly cost of the interferon-alpha used in our study is $5953 compared with a median of $24 375 for the higher doses used by other investigators. Less toxicity was also observed. Conclusion: Low-dose interferon-alpha is as effective as higher-dose interferon-alpha in inducing remissions and prolonging survival in patients with chronic myeloid leukemia but is considerably less expensive and toxic.