Very poor outcome of leukemic transformation in myelofibrosis: a single center experience with 13 patients

A Concise Update on Risk Factors, Therapy, and Outcome of Leukemic Transformation of Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPN) in chronic phase that evolve into blast phase (BP) hold a dismal prognosis and represent an urgent unmet clinical need. The mutational landscape of MPN-BP is distinct from de novo acute myeloid leukemia and offers insight into molecular mechanisms contributing to clonal evolution providing potential novel drug targets. A number of retrospective studies have identified patient- and disease-specific variables associated with increased risk of leukemic transformation (LT) of an underlying MPN. Several prognostic models have been developed to identify those MPN patients at highest risk for LT that may warrant early aggressive therapeutic intervention. Acute myeloid leukemia-type induction chemotherapy does not offer a significant survival benefit for MPN-BP unless followed by hematopoietic stem-cell transplantation. Unfortunately, most patients with MPN-BP are not candidates for hematopoietic stem-cell transplantation as a result of advanced age, competing comorbid conditions, or lack of an acceptable donor graft option. JAK2 inhibitor monotherapy is effective in reducing splenomegaly and symptom burden in the majority of treated patients with myelofibrosis, but LT can still occur. High-dose JAK2 inhibitor monotherapy appears tolerable but only modestly active in the treatment of MPN-BP. Current JAK2 inhibitor-based combination therapy approaches are supported by preclinical investigation and are currently being tested in multicenter clinical trials.

Pathogenesis and management of acute myeloid leukemia that has evolved from a myeloproliferative neoplasm

PURPOSE OF REVIEW

The myeloproliferative neoplasms (MPNs), including essential thrombocythemia, polycythemia vera and primary myelofibrosis (PMF), are a heterogeneous group of myeloid-derived chronic haematopoietic malignancies. Frequent clinical consequences of these diseases include not only an increased risk of thrombosis but also leukemic transformation, which carries a particularly poor prognosis. Here, we discuss the recent identification of risk factors for leukemic transformation, elucidate mechanisms contributing to leukemic transformation, as well as highlight the development of new treatment strategies.

RECENT FINDINGS

Significant progress in the understanding of the biology of MPNs has been made in recent years, particularly with the discovery that mutations in the JAK-STAT signaling pathway cause unregulated activation. These genetic insights have been extended to leukemic transformation and have revealed a host of genetic alterations that occur at the time of transformation, and that may identify patients at risk for leukemic transformation. Such studies have demonstrated that acute myeloid leukemia (AML) evolved from a chronic phase MPN is distinct from de-novo AML both genetically and clinically given its resistance to conventional antileukemic therapy.

SUMMARY

Leukemic transformation of an MPN remains a significant clinical challenge. Recent advances in the understanding of the molecular events that contribute to the development of leukemic transformation will need to be utilized in order to produce rational therapeutic approaches for this largely fatal disease.