Role of interferon alpha‐2a in the treatment of polycythemia vera

We studied the effects of recombinant interferon alpha‐2a (IFN‐alpha) in 36 patients with polycythemia vera (PV) previously treated with phlebotomy and/or conventional cytostatic agents. In each patient, after at least 2 months of discontinuation of any cytotoxic therapy, the hematocrit (Hmt) was first brought to normal value by phlebotomy; IFN‐alpha treatment was then begun at a starting dose of 3,000,000 IU s. c. three times a week. Response to treatment, which was assessed monthly, was defined as persistent normalization of Hmt without concomitant phlebotomy; in non‐responsive patients the initial IFN‐alpha weekly dosage was progressively increased. Twenty patients were responsive with a median duration of response of 7 months (range 2‐25+ months); out of these, 7 patients are still under treatment and responsive at 13+, 17+, 20+, 22+, 23+, 25+, 25+ months. These findings indicate that a cohort, although small, of patients with PV (19.4%) are persistently sensitive to IFN‐alpha; in this subset of patients, this cytokine can therefore provide a useful treatment option, since, contrary to conventional therapeutic approaches such as radioactive phosphorus, cytostatic agents, or phlebotomy, IFN‐alpha is devoid of harmful side effects. ©1995 Wiley‐Liss, Inc.