The effect of interferon alpha on myeloproliferation and vascular complications in polycythemia vera

The effect of interferon alpha (IFN) on myeloproliferation and vascular com plications was studied in 32 patients (17 female, 15 male; median age 60.5 yr) with polycythemia vera (PV). IFN therapy was initiated at a median time of 19 months after diagnosis. Ten patients were pretreated with chemothera py in addition to phlebotomy. IFN dose was 12 megaU/wk during the first yea r, 9 megaU/wk during the second year and 12 megaU/wk thereafter. During IFN alpha treatment hematocrit level was 45.7% and remained at this level afte r the second year of treatment, compared to 46.5% before IFN. The frequency of phlebotomy before IFN was 0.49/month and dropped to 0.19/month (p < 0.0 005) during the first year of IFN treatment. IFN normalized high platelet a nd leukocyte counts in a majority of patients. The incidence of deep venous thromboses was 3.6%/yr before IFN alpha and 1.8%/yr during the first year of treatment. IFN-induced side-effects were mainly flu-like symptoms, fever , fatigue and arthralgia. In conclusion, IFN allowed the reduction of the d ose of chemotherapy and decreased the need of phlebotomy. Despite improveme nt of hematological parameters, it is still uncertain whether IFN alpha can improve clinical symptoms in PV.