Accelerated Phase of Myeloproliferative Neoplasms

Acta Haematol. 2021;144(5):484-499. doi: 10.1159/000512929. Epub 2021 Apr 21.


Background: Myeloproliferative neoplasms (MPNs) can transform into blast phase MPN (leukemic transformation; MPN-BP), typically via accelerated phase MPN (MPN-AP), in ∼20-25% of the cases. MPN-AP and MPN-BP are characterized by 10-19% and ≥20% blasts, respectively. MPN-AP/BP portend a dismal prognosis with no established conventional treatment. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the sole modality associated with long-term survival.

Summary: MPN-AP/BP has a markedly different mutational profile from de novo acute myeloid leukemia (AML). In MPN-AP/BP, TP53 and IDH1/2 are more frequent, whereas FLT3 and DNMT3A are rare. Higher incidence of leukemic transformation has been associated with the most aggressive MPN subtype, myelofibrosis (MF); other risk factors for leukemic transformation include rising blast counts above 3-5%, advanced age, severe anemia, thrombocytopenia, leukocytosis, increasing bone marrow fibrosis, type 1 CALR-unmutated status, lack of driver mutations (negative for JAK2, CALR, or MPL genes), adverse cytogenetics, and acquisition of ≥2 high-molecular risk mutations (ASXL1, EZH2, IDH1/2, SRSF2, and U2AF1Q157). The aforementioned factors have been incorporated in several novel prognostic scoring systems for MF. Currently, elderly/unfit patients with MPN-AP/BP are treated with hypomethylating agents with/without ruxolitinib; these regimens appear to confer comparable benefit to intensive chemotherapy but with lower toxicity. Retrospective studies in patients who acquired actionable mutations during MPN-AP/BP showed positive outcomes with targeted AML treatments, such as IDH1/2 inhibitors, and require further evaluation in clinical trials. Key Messages: Therapy for MPN-AP patients represents an unmet medical need. MF patients, in particular, should be appropriately stratified regarding their prognosis and the risk for transformation. Higher-risk patients should be monitored regularly and treated prior to progression to MPN-BP. MPN-AP patients may be treated with hypomethylating agents alone or in combination with ruxolitinib; also, patients can be provided with the option to enroll in rationally designed clinical trials exploring combination regimens, including novel targeted drugs, with an ultimate goal to transition to transplant.

Keywords: Accelerated phase myeloproliferative neoplasms; Blast phase myeloproliferative neoplasms; Myelofibrosis; Myeloproliferative neoplasms; Post-myeloproliferative neoplasm acute myeloid leukemia.

Publication types

  • Review

MeSH terms

  • Allografts
  • Blast Crisis* / genetics
  • Blast Crisis* / metabolism
  • Blast Crisis* / pathology
  • Blast Crisis* / therapy
  • Hematopoietic Stem Cell Transplantation*
  • Humans
  • Leukemia, Myeloid, Acute* / genetics
  • Leukemia, Myeloid, Acute* / metabolism
  • Leukemia, Myeloid, Acute* / pathology
  • Leukemia, Myeloid, Acute* / therapy
  • Mutation*
  • Myeloproliferative Disorders* / genetics
  • Myeloproliferative Disorders* / metabolism
  • Myeloproliferative Disorders* / pathology
  • Myeloproliferative Disorders* / therapy
  • Neoplasm Proteins* / genetics
  • Neoplasm Proteins* / metabolism


  • Neoplasm Proteins