Accelerated and blast phase myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) have an inherent risk of transformation into blast phase (MPN-BP) or accelerated phase (MPN-AP) which is characterized by presence of ≥20% or 10-19% peripheral blood or bone marrow blasts, respectively. Primary myelofibrosis (PMF) is associated with the highest risk of blastic transformation (14.2%), followed by polycythemia vera (PV) (6.8%) and essential thrombocythemia (ET) (3.8%). Risk of leukaemic transformation (LT) in PMF can be determined by a three-tiered model based on presence of IDH1 mutation, circulating blasts ≥3%, SRSF2 mutation, age >70 years, ASXL1 mutation, and moderate/severe anemia with high, intermediate, and low risk groups (LT incidence 57%, 17%, and 8%, respectively). Currently, treatment of MPN-AP/BP includes acute myeloid leukaemia (AML)-like induction chemotherapy or hypomethylating agents alone or in combination with venetoclax and/or ruxolitinib. In transplant-eligible patients, our goal is to achieve complete remission with or without count recovery, before proceeding with allogeneic stem cell transplantation, which is the only modality associated with long-term survival. In the current review, we discuss our diagnostic, prognostic, and therapeutic approach to patients with MPN-AP/BP.