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/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-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% CI, 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.