Outcomes of allogeneic transplantation in blast-phase myeloproliferative neoplasms: one-third achieve long-term survival.

Philadelphia-negative myeloproliferative neoplasms (MPNs) can progress to blast phase (MPN-BP), a biologically distinct and highly lethal entity with a median survival typically under six months. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only potentially curative approach, yet relapse and non-relapse mortality limit durable benefit. We retrospectively analyzed post-transplant outcomes in 51 consecutive adults undergoing 53 allo-HSCTs for MPN-BP. Median age was 62 years; most cases evolved from myelofibrosis, and JAK2 was the predominant driver mutation. Neutrophil engraftment occurred in all but two patients (median 12 days). At 1-year, cumulative incidences were 35.8% for grade II-IV acute GVHD, 7.5% for moderate-severe chronic GVHD, 44.3% for relapse, and 25.8% for non-relapse mortality. One-year overall survival (OS) and disease-free survival were 43.4% and 37.7%, respectively; relapse was the leading cause of death. In multivariable analysis, TP53 mutations and higher peripheral blast burden adversely affected OS, while CALR mutations appeared to be associated with improved OS, peripheral blasts also independently predicted relapse. These data underscore the cure rate of approximately one-third of MPN-BP and highlight peripheral blasts and TP53 as actionable risk markers for transplant strategies.