Platelet recovery delay and survival in patients with myelofibrosis undergoing allogeneic hemopoietic stem cell transplantation

We studied platelet recovery in 93 patients with myelofibrosis, following an allogeneic hemopoietic stem cell transplant (HSCT). The primary end point of the study was achieving a platelet count of 50x109/L within day +100 post transplant, which occurred in 62 patients (67%), predicted 5-year non-relapse mortality (NRM) (5% vs. 55%, P=0.0009) and 5-year actuarial survival (85% vs. 38%, P<0.00001); relapse was unaffected. The cumulative incidence of strong platelet recovery was predicted by a matched sibling donor (MSD) compared to alternative donors (90% vs. 60%, P=0.001), by the dose of CD34+ cells (cut off 8.68x106/kg; 83% vs. 61%, P=0.01), recipient age (cut off 63 years; 72% vs. 48%, P=0.01), and splenectomy (86% vs. 63%, P=0.04). In multivariate Cox analysis, significant predictors of platelet recovery were a MSD (P=0.003), a high CD34 cell dose (P=0.02), splenectomy (P=0.003), and younger patient age (P=0.02). Patients with slow platelet recovery have significantly lower platelet counts long term, combined with chronic graft-versus-host disease. In conclusion, strong post-HSCT platelet recovery in MF patients is mainly predicted by donor type, together with CD34 cell dose and patient age, and is strongly associated with NRM and survival.