Sequential evaluation of alpha-2b-interferon treatment in 128 patients with hairy cell leukemia.

This multicenter study reports on 128 patients with hairy cell leukemia (HCL) who were treated subcutaneously with alfa-2b interferon (Intron A, Schering Corp, Kenilworth, NJ), three times a week at a dosage of 2 megaunits/m2. Five patients (4%) had a complete response (CR) with virtual eradication of hairy cells from the bone marrow, 98 (77%) showed a partial response (PR), defined as hematologic normalization of all three blood counts associated with decreased hairy cells in the bone marrow, and nine (7%) showed a minor response (MR) that included improvement in at least one measurement of the blood count. Sixteen persons (12%) did not respond. Thirteen of the 128 had had neither a splenectomy nor a CR. Responders who completed 12 months of interferon therapy were randomized to either an additional 6 months of therapy or to observation only. Relapses occurred in six of 35 (18%) randomized to observation alone and in two of 29 (7%) who continued interferon therapy. The relapses are too few to draw conclusions; however, 27 responders have remained off interferon treatment for greater than 6 months; cessation of interferon therapy does not result in a rapid deterioration of peripheral blood counts. In HCL, interferon therapy produced a large percentage of durable objective responses in the majority of patients. The exact duration of this response and the results of retreatment are yet undetermined.