Sustained Remission After Interferon Treatment for Essential Thrombocythemia

Abstract

Essential thrombocythemia (ET) is a myeloproliferative disorder of clonal origin [1] resulting in excessive production of platelets [2,3] and in an increased risk of thrombohemorrhagic complications. The Polycythemia Vera Study Group (PVSG) has proposed a number of diagnostic criteria to exclude the remaining chronic myeloproliferative disorders with elevated platelet counts and other conditions potentially causing thrombocytosis [4]. The aim of treatment for patients with ET is the prevention of thrombotic and/or hemorrhagic complications. Control of thrombocytosis and attributable symptoms is obtained in the majority of patients by myelosuppressive therapy, e.g., radioactive phosphorus, busulphan, chlorambucil, melphalan, pipobroman, and hydroxyurea [5–11]. Rapid and prolonged remission has been frequently achieved but continuous treatment for maintaining remission, as well as treatment complications such as induction of unwarranted bone marrow aplasia or secondary malignancy, limit the usefulness of these cytotoxic drugs. Interferon-a (IFN-α) is effective in cases of ET and excessive thrombocytosis in myeloproliferative diseases [12–15]. We report results from studies of 12 patients with ET receiving recombinant IFN-α_2b (rIFN-α_2b), some of whom have achieved an unmaintained remission for more than one year.