Efficacy and safety of pegylated-interferon-2a in myelofibrosis: a study by the FIM and GEM French cooperative groups

Myeloproliferative neoplasm-related myelofibrosis is associated with cytopenic or proliferative phases, splenomegaly and constitutional symptoms. Few effective treatments are available and small series suggested that interferon could be an option for myelofibrosis therapy. We performed a retrospective study of pegylated-interferon alpha-2a (Peg-IFN alpha-2a) therapy in myelofibrosis. Sixty-two patients treated with Peg-IFN alpha-2a at 17 French and Belgian centres were included. Responses were determined based on the criteria established by the International Working Group for Myelofibrosis Research and Treatment. Mean follow-up was 26months. Sixteen of 25 anaemic patients (64%) (eight concomitantly receiving recombinant erythropoietin) achieved a complete response and transfusion-independence was obtained in 5/13 patients (385%). Constitutional symptoms resolved in 82% of patients. All five leucopenic patients normalized their leucocyte counts, whereas a normal platelet count was obtained in 5/8 thrombocytopenic patients. Splenomegaly was reduced in 465% of patients, and complete resolution of thrombocytosis and leucocytosis were observed in 828% and 688% of patients, respectively. Side effects (mostly haematological) were mainly of grade 1-2. The only factor independently associated with treatment failure was a spleen enlargement of more than 6cm below the costal margin. In conclusion, Peg-IFN alpha-2a induced high response rates with acceptable toxicity in a large proportion of patients with primary and secondary myelofibrosis, especially in early phases.