Interferon treatment for hairy cell leukemia: an update on a cohort of 69 patients treated from 1983-1986.

This report documents the follow-up information on 69 hairy cell leukemia (HCL) patients treated with interferon alpha-2b (IFN) as primary treatment from 1983-86. Follow-up through October 1991 shows only 11 patients have died. Forty-one of the 57 patients completing the intended 12 or more months of initial IFN treatment were eventually considered IFN failures. Thirty-nine required retreatment (38 received a second course of IFN and one received pentostatin). Two patients died without further therapy for HCL. The median time to interferon failure was 33 months. Sixteen patients are alive and have not required further treatment after completing their initial 12 or more months of interferon. Eight patients underwent a third course of interferon therapy at a median time after completion of a second course of IFN of 1.3 years. Seven patients developed a second malignancy; three of these patients developed a high-grade lymphoma between 3.5 and 6.5 years after initiation of interferon therapy. We conclude that although interferon provides excellent palliation, most patients will eventually require further treatment with interferon or chemotherapy. Future trials in HCL must be aware of second malignancies as a common cause of death.