Objective: To determine the toxicity and efficacy of low-dose interferon-α 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-α 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-α at a dose of 2 × 106 U/m2 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-α.
Results: 70% of patients treated with low-dose interferon-α 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-α 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% CI, 51% to 95%), which compares favorably with survivals reported by investigators who used higher doses. The estimated yearly cost of the interferon-α 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-α is as effective as higher-dose interferon-α in inducing remissions and prolonging survival in patients with chronic myeloid leukemia but is considerably less expensive and toxic.