Demonstrated benefit of continuous interferon-alpha-2b therapy in hairy cell leukemia. A two-year follow-up

Interferon-alpha-2b (IFN) was given to a series of 50 patients with hairy cell leukemia (HCL). The IFN dose for both induction and maintenance was 2.0 × 10⁶ IU/m² s.c. three times weekly. At 24 months 38 patients remained in the study. The proportion of complete responders (CR) increased during the follow-up, and had at 24 months reached 58%, while 28% at the same time had a partial (PR) and 14% a minor response (MR). During the two years of continuous IFN treatment none of the 38 patients showed any signs of relapse. The response rate was similar between splenectomized (n = 15) and non-splenectomized (n = 23) patients, but the rise in platelets was much steeper and reached a significantly higher plateau in patients, who previously had undergone splenectomy. The IFN therapy was generally well tolerated, but when evaluated at 24 months at least some (mostly mild) toxicity was noted in 76% of the patients. None of the patients developed neutralizing antibodies to IFN.