What are the options for maintenance therapy for polycythemia vera (PV)?

Updated: Sep 20, 2021
  • Author: Srikanth Nagalla, MD, MS, FACP; Chief Editor: Sara J Grethlein, MD, FACP  more...
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Once the patient's hemoglobin and hematocrit values are reduced to within the reference range, implement a maintenance program either by inducing iron deficiency by continuous phlebotomies (the frequency of the procedure depends on the rate of reaccumulation of the red blood cells) or by using a myelosuppressive agent. The choice depends on the risks of secondary leukemias and the rate of thrombosis or bleeding. Patients must be cautioned to not take iron supplements.

The risks for secondary leukemia depend on the type of therapy (eg, phlebotomy, chlorambucil) or the type of myelosuppressive agents (eg, hydroxyurea [HU], anagrelide, interferon alfa) and duration of therapy.

The Polycythemia Vera Study Group (PVSG) demonstrated a decreased survival rate and increased mortality rate from acute leukemia in the first 5 years, and a total of 17% of patients had leukemia after 15 years with chlorambucil and with32 P. [30] Increased risk of leukemia was also found with use of phosphorus-32; production of this radionuclide has been discontinued and it is no longer available in the United States or elsewhere.

An increased incidence of thrombotic complications occurred in the phlebotomy arm. This indicates that phlebotomy is not ideal for patients with elevated platelet counts and previous thrombosis, as are observed in patients who are older. In this situation, using HU has decreased these complications.

Hydroxyurea has been the mainstay therapy for PV since the PVSG results indicated it is an effective agent for myelosuppression; however, concerns have been raised regarding long-term risks for leukemic transformation. [31] In the PVSG trial, HU therapy reduced the risk of thrombosis compared with phlebotomy alone; the PVSG recommended that HU should be the drug of choice for patients older than 40 years. [32]

The role of HU in leukemic transformation is not clear. Several nonrandomized studies have supported or refuted a significant rise in leukemic conversion with the long-term use of HU in patients with essential thrombocythemia (from 0% to 5.5%) and in patients with PV (from 2.1% to 10%).

The PVSG closed the chlorambucil arm because of increased rates of acute leukemia after 7 years. However, in the 15-year follow-up of the HU arm compared with the phlebotomy-alone arm, the trend for leukemic transformation was greater in the HU arm but the differences did not meet statistical significance. Followup for a median of 8.6 years and a maximum of 795 weeks showed that 5.4% of patients developed leukemia in the HU arm compared with 1.5% of patients treated with phlebotomy alone.

Other case series have reported secondary leukemia in 3-4% of patients, which is relatively low compared with the benefits of preventing thrombotic complications.

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