Outcomes after Allogeneic Hematopoietic Cell Transplant in patients diagnosed with Blast Phase of Myeloproliferative Neoplasms: a retrospective study from the Chronic Malignancies Working Party of the EBMT.

Allogeneic haematopoietic cell transplant (allo-HCT) provides the only potential route to long-term remission in patients diagnosed with blast phase transformation of myeloproliferative neoplasm (BP-MPN). We report on a large, retrospective EBMT registry-based study of BP-MPN patients undergoing allo-HCT. BP-MPN patients undergoing first allo-HCT between 2005-2019 were included. A total of 663 patients were included. With a median follow-up of 62 months, the estimated 3-year OS was 36% (95% CI, 32-36). Factors associated with lower OS were Karnofsky Performance Status (KPS) <90 (HR 1.65, p<0.001) and active disease at allo-HCT (HR 1.45, p<0.001), whereas patients undergoing allo-HCT more recently associated with a higher OS (HR 0.96, p=0.008). In a selected patients population, the 3-year OS of patients undergoing allo-HCT in complete response (CR) and with a KPS ≥90 was 60%. KPS<90 (HR 1.4, p=0.001) and active disease (HR 1.44, p=0.0004) were associated with a lower PFS. Conversely, most recent allo-HCT associated with a higher PFS (HR 0.96, p=0.008). Active disease at allo-HCT (HR 1.34, p=0.03) was associated with a higher cumulative incidence of relapse (RI) and allo-HCT in earlier calendar years (HR 0.96, p=0.02) associated with a lower RI. Lastly, KPS<90 (HR 1.91, p<0.001), active disease (HR 1.74, p=0.003) and allo-HCT from mismatched related donors were associated with a higher NRM (HR 2.66, p=0.003). In this large series of BP-MPN patients, about one third were alive at 3 years after transplantation. Patients undergoing allo-HCT in the more recent era, with a KPS≥90 and in CR at transplant had a better prognosis. This article is protected by copyright. All rights reserved.