Treatment of polycythemia vera by isovolemic large-volume erythrocytapheresis

Excess red blood cells (RBC) in patients with polycythemia vera (PV) are usually removed by repeated phlebotomy. In order to improve the efficacy of this treatment, we used isovolemic large-volume erythrocytapheresis (EA) by a cell separator. A retrospective analysis of our experience with 69 PV patients (206 EA procedures) is reported. EA induced a rapid, well-tolerated, and long-lasting reduction of Hct, Hb, and RBC counts, as well as an immediate disappearance or reduction of clinical symptoms of PV, while tissue oxygen tension — as measured in 8 patients — increased. Hct was reduced by EA from 56.8% ±5.6% to 41.9% ±6.6%, Hb from 17.5±2.3 to 12.7±2.4 g%, RBC counts from 7.±0.9 to 5.4±0.9×106/mm3. The mean volume of the apherisate was 1410±418 ml, (mean Hct 79.7%±9.3%), and the actual RBC volume removed 1113±367 ml. The isovolemic procedure was well tolerated and the acceptance by patients seemed to be better than with repeated phlebotomy. In 21 patients whose Hct values (Hct before and after EA 58%±5.7% and 41.5%±4.9%) were regularly followed after EA the mean period with Hct<50% after a single EA procedure was 6.1±4.1 months (median, 6); in 14 out of these 21 patients a Hct of <43% after EA was reached and their mean period with Hct<50% after EA was 7.6±4.0 months (median, 7.5). For three patients this period was 11, 13, and 15 months, respectively. In our experience large-volume isovolemic EA is a feasible, very effective, and welltolerated alternative treatment modality for PV patients. It may be superior to repeated phlebotomy, especially for patients with excessively increased RBC mass. Only a controlled prospective trial can answer the question, whether EA, due to its rapid effect and due to the long-lasting lower RBC mass, leads to a lower rate of thromboembolic events, and whether EA may delay the necessity for treatment of PV by cytotoxic drugs or P32.