Myeloproliferative neoplasms: pathophysiology and therapeutic strategy

Abstract

Myeloproliferative neoplasms (MPNs) arise from hematopoietic stem cells (HSCs) with genetic abnormalities in combination with mutations in JAK2, MPL or CALR, which induce autosomal JAK-STAT pathway activation, and mutations in epigenetic regulator genes such as TET2 or DNMT3A. The prognosis of patients with polycythemia vera (PV) or essential thrombocythemia (ET) is relatively good, and the therapeutic goal in cases with PV or ET is to prevent thrombohemorrhagic complications. PV or ET patients at least 60 years of age or with a history of thrombosis are in a high-risk category, and are managed with low dose aspirin and cytoreductive therapy. Phlebotomy to maintain Ht<0.45 is also used to manage PV patients. The median survival for Japanese primary myelofibrosis (MF) patients is 3.9 years. Several factors including age>65 years, Hb<10 g/dl, the presence of constitutional symptoms, and the presence of blasts in blood were identified as being associated with shorter survival in MF patients. Those patients in the high-risk category are candidates for allogenic HSC transplantation (allo-HSCT), which is potentially curative but is also associated with higher therapy-related mortality. High-risk MF patients without indications for allo-HSCT are treated with JAK inhibitors, which can markedly ameliorate constitutional symptoms and splenomegaly, and might thereby lead to a degree of improvement in survival.