Medication Summary
Chemotherapeutic cytoreductive therapy is used in all patients who are high risk but not in those who are low risk. All patients receive low-dose aspirin.
Biologic response modifiers
Class Summary
Biologic response modifiers elicit antiproliferative, antiviral, and immunomodulating effects. They inhibit cellular growth and alter cellular differentiation.
Interferon alfa-2a, recombinant (Pegasys)
Protein produced in response to viral infection and other inflammatory stimuli. The exact mechanism is unknown, but it is believed to exert an antiproliferative effect. Produced by recombinant DNA techniques in E coli. In polycythemia vera and ET, it has shown to have long term efficacy, and reduces JAK2 allelic burden. Sporadic case reports have noted cytogenetic remissions, suggesting a possible biologic effect.
Antiplatelet agents
Class Summary
These agents prevent formation of thrombi-associated polycythemia.
Aspirin (Anacin, Ascriptin, Bayer)
Irreversibly acetylates platelet cyclooxygenase, resulting in a decrease in thromboxane A2, the prostaglandin responsible for platelet shape change, granule release, and aggregation. Prescribed for most patients with polycythemia vera.
Anagrelide (Agrylin)
Inhibits post mitotic megakaryocyte maturation. Unlike hydroxyurea, selectively inhibits platelet proliferation. In polycythemia vera used only to control platelet counts, but shows slight decrease in mean hemoglobin and hematocrit while white cell counts maintained. Inhibits cyclic nucleotide phosphodiesterase and the release of arachidonic acid from phospholipase, possibly by inhibiting phospholipase A2. Can be used in addition to hydroxyurea for particularly difficult to control thrombocytosis in polycythemia vera.
Antineoplastic Agent
Class Summary
These agents are used off-label for polycythemia, but pediatric doses are extrapolated from pediatric treatment regimens, including leukemia and myelodysplastic syndrome.
Hydroxyurea (Droxia, Hydrea)
Nonalkylating, myelosuppressive, S-phase agent. Inhibits ribonucleotide reductase, the enzyme that converts ribonucleotides into deoxynucleotides, thereby depleting deoxynucleotide and inhibiting DNA synthesis. Cellular proliferation is ultimately inhibited, and leukocytes, erythrocytes, and platelets are decreased. The mechanism of action is probably different than the one exerted by hydroxyurea in the treatment of sickle cell disease. A misconception is that hydroxyurea is leukemogenic. No studies have conclusively demonstrated that hydroxyurea is more leukemogenic than baseline in myeloproliferative disease.
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Bone marrow film at 400X magnification demonstrating dominance of erythropoiesis. Courtesy of U. Woermann, MD, Division of Instructional Media, Institute for Medical Education, University of Bern, Switzerland.
