Thalidomide and lenalidomide in primary myelofibrosis

Primary myelofibrosis is a clonal haematopoietic stem cell disease, characterised by marrow stromal fibrosis, extramedullary haematopoiesis, splenomegaly, hepatomegaly and progressive cytopenia. Therapeutic options once cytopenia has developed are limited to supportive care, such as erythrocyte transfusions and growth factors. The aetiology has become more clear, especially since JAK-2 mutations were found, resulting in increased production of cytokines. The immune-modulating drug thalidomide and its derivative lenalidomide have shown to be effective in reducing cytopenia, most probably by inhibiting the cytokine responses. In some patients the bone marrow fibrosis disappears. We describe the experience with these drugs in a cohort of 14 patients for thalidomide and seven for lenalidomide (in six patients lenalidomide was given after thalidomide and one patient received lenalidomide upfront). Thalidomide gave clinical improvement in 6/14 patients, but its use was limited mainly due to toxicity, especially the development of neuropathy. The drug could be given for a median period of 15.5 months in responding patients. Lenalidomide was effective in 4/7 of the patients, in some patients with no response on thalidomide. Due to the more favourable toxicity profile, the median duration of therapy was 19 months, with 3/4 patients on therapy longer than 19 months. These data are discussed in view of the clinical studies published. We conclude that lenalidomide is preferred in myelofibrosis, given a higher response rate and more favourable toxicity profile. If no response the addition of prednisone can be considered. In some patients it can normalise haemoglobin and make them transfusion independent.