Prolonged, Continuous Treatment of Hairy Cell Leukemia Patients With Recombinant Interferon-da

Interferons are not curative in hairy cell leukemia (HCL), and retreatment is necessary in most patients whose therapy is stopped. In an attempt to maintain or improve responses, we administered recombinant interferon-da (rlFN-da) continuously to patients with HCL who initially responded to this therapy. Of 53 evaluable patients enrolled in this study, 32 have received rlFN-da continuously for a median of 5 years. Patients received 3 million units of rlFN-da subcutaneously (SC) daily for 6 months, followed, in responding patients, by the same dose three times weekly. Twenty-one patients (40%) discontinued IFN after a median of 29 months, seven of whom developed resistant disease in association with antiIFN antibodies. Treatment produced high response rates: complete response plus partial response (CR + PR) = 40 of 53 (76%). CR + PR + minor response (MR) = 43 of 53 (82%), with no differences in response rates between patients with