New and old treatment modalities in primary myelofibrosis

The treatment of primary myelofibrosis (PMF) remains essentially palliative. Conventional modalities include a wait-and-see approach for asymptomatic patients, oral cytolytic drugs such as hydroxyurea for the hyperproliferative forms of the disease, androgens or erythropoietin for the anemia, and splenectomy in selected patients. These therapeutic modalities improve the patients' quality of life but have no impact on survival. Newer therapies for PMF are currently being used. Antiangiogenic and immunomodulatory drugs such as thalidomide and lenalidomide are associated with frequent side effects but have shown certain efficacy, especially for the anemia and thrombocytopenia. The association of low-dose thalidomide with prednisone has better tolerability, and it is also effective. Tyrosine kinase inhibitors such as imatinib have also been used, but their efficacy is limited. Tipifarnib, a farnesyltransferase inhibitor, has shown certain effects in the anemia. Allogeneic stem cell transplantation (SCT) is the only curative therapy for PMF. Its standard modality has an associated mortality of 30%, and it is indicated in younger patients with high-risk disease or disease resistant to conventional treatment. Reduced-intensity conditioning allogeneic SCT is associated with low mortality while maintaining a curative potential, and until longer follow-up is available, it can be used in patients aged 45-70 years old with high- or intermediate-risk myelofibrosis or myelofibrosis resistant to treatment. Autologous SCT is a palliative measure that can be considered in patients with resistant disease, who lack a suitable donor. Newer immunomodulatory drugs, proteasome inhibitors, hypomethylating agents, and JAK2 inhibitors are currently being tested.