Allogeneic hematopoietic stem cell transplantation with fludarabine, busulfan, and thiotepa conditioning is associated with favorable outcomes in myelofibrosis

Allogeneic stem cell transplantation is a curative therapy for myelofibrosis. The optimal conditioning regimen has not been well defined. We retrospectively compared transplantation outcomes in patients with myelofibrosis (n = 67) conditioned with myeloablative (MAC, 36%) and reduced-intensity (RIC, 46%) regimens, and more recently with the combination of thiotepa, busulfan, and fludarabine (TBF, 18%). Patients were transplanted from HLA-matched sibling (n = 26) or unrelated donors (n = 41) between the years 2003 and 2018. The median follow-up was 2.9 years for all patients but shorter in the TBF group (1.1 years). The probability of 3-year progression-free survival (PFS) was 43%. At 1 year, the rate of PFS was 80%, 54%, and 45% with TBF, MAC, and RIC, respectively (p = 0.031). In a multivariable model, there was a greater risk for death with MAC (hazard ratio [HR] 12.26, p = 0.026) and lower PFS with both MAC (hazard ratio [HR] 7.78, p = 0.017) and RIC (HR 5.43, p = 0.027) compared with TBF. Relapse was higher with RIC (HR 8.20, p = 0.043) while nonrelapse mortality was increased with MAC (HR 9.63 p = 0.049). Our results indicate that TBF is a promising preparative regimen in myelofibrosis patients transplanted from matched sibling or unrelated donors, and should be further explored.