Transplant Decisions in Patients with Myelofibrosis: Should Mutations Be the Judge?

The prognosis of myeloproliferative neoplasms, including primary myelofibrosis (PMF), polycythemia vera, and essential thrombocythemia varies considerably, between these disorders as well as within each diagnosis. Molecular studies have identified "driver mutations" in JAK2, MPL1, and CALR and additional somatic DNA mutations, including ASXL1, EZH2, IDH1/2, and SRSF2, that affect prognosis differentially. Patients with mutations in CALR (type1) have a better outlook than patients with mutations in JAK2 or MPL, whereas patients without any of the driver mutations (triple negative) have the shortest life expectancy. Mutations in ASXL1, EZH2, and SRSF2 may be associated with shortened survival, and IDH mutations carry a higher risk of leukemic transformation. The combination and number of mutations are more important than a given single mutation. Mutations also appear to impact the outcome of hematopoietic cell transplantation (HCT), currently the only treatment with curative potential. Based on available data, the best post-HCT outcome is observed with CALR mutations. Triple negativity has a negative impact. The data on JAK2 are controversial. Mutations in ASXL1 or IDH1/2 reduce the probability of progression-free survival after HCT, although the impact of ASXL1 differs between patients with primary and secondary myelofibrosis. Although it is not clear to what extent HCT can overcome the risks associated with a given mutational pattern, at present, early HCT should be considered in triple-negative patients and patients with PMF who harbor mutations in ASXL1. Mutations in EZH2, SRSF2, or IDH, particularly if combined with other mutations, should also lead to consideration of HCT. Further studies are needed to validate the present observations and determine the impact of additional mutations that have been identified.