Abstract
Essential thrombocythemia (ET) and polycythemia vera (PV) are chronic clonal myeloid
disorders that originate from the multipotential hematopoietic stem cell. They are
characterized, respectively, by excessive thrombocytosis and erythrocytosis, a high
incidence of thrombohemorrhagic events, vasomotor symptoms, and an inherent tendency
to undergo leukemic transformation. Current standard therapies to control the excess
accumulation of myeloid cells and to provide symptomatic relief carry either a persistent
risk of thrombosis, as in the case of phlebotomy, or, in the case of hydroxyurea,
the potential for inducing leukemia. None alter the natural history of these diseases.
Interferon-α has been shown to have potent antiproliferative effects on the hematopoietic
stem cells and bone marrow fibroblasts and, as a result, has received much attention
as a therapeutic agent for chronic myeloproliferative disorders. The ability of interferon-α
to induce hematologic and cytogenetic remission in chronic phase chronic granulocytic
leukemia has further increased interest in this agent. Interferon-α has shown therapeutic
activity in PV and ET, as demonstrated in multiple small studies and singlearm trials
reviewed in this article. Reported beneficial effects include the ability to control
excessive erythrocytosis and thrombocytosis and such diseaserelated features as vasomotor
symptoms, pruritus, and splenomegaly. Recent reports of cytogenetic remission and
reversal of bone marrow fibrosis after interferon therapy are of interest. Advantages
over current therapeutic standards include lack of known leukemogenic and teratogenic
effects and the potential to alter the underlying course of disease. Nevertheless,
none of the information available allows definite therapeutic recommendations for
the use of interferon-α in PV or ET. The available data support the need for randomized
controlled trials comparing interferon-α with standard therapy.
Keywords:
Essential thrombocythemia - pathogenesis - polycythemia vera - side effects - treatment
