International working group for myelofibrosis research and treatment response assessment and long-term follow-up of 50 myelofibrosis patients treated with thalidomide-prednisone based regimens.

We have previously reported the benefits of combination therapy with thalidomide and prednisone for the improvement of cytopenias and splenomegaly for patients with myelofibrosis (MF); both primary and those arising from an antecedent polycythemia vera (PV) and essential thrombocythemia (ET). We report here the overall efficacy of three different thalidomide-prednisone based regimens (alone or in combination with either oral cyclophosphamide for three months or continuous weekly etanercept) when assessed by the IWG-MRT response criteria which were developed after completion of these studies. Additionally we report on the durability of response and long-term follow-up. We observed an overall response rate of 28% by IWG-MRT criteria (mostly clinical improvement - 22% anemia, 8% splenomegaly) with a median duration of response of 8.5 months. Toxicities primarily consisted of neuropathy (Grade 3 or higher neuropathy in 6%) and cytopenias (Grade 3 or higher in 20%). After a median follow-up of three years, fourteen patients (28%) had expired from MF at the time of this analysis with median survival of 36 months.