Poor Outcomes of HLA-Mismatched Allogeneic Hematopoietic Cell Transplantation and High Ferritin Levels after a Reduced-Intensity Conditioning Regimen in Patients with Advanced Myelofibrosis

Allogeneic hematopoietic cell transplantation (allo-HCT) preconditioning intensity, donor choice, and graft-versus-host disease (GVHD) prophylaxis for advanced myelofibrosis (MF) have not been fully elucidated. Thirty-five patients with advanced MF were treated with reduced-intensity conditioning (RIC) allo-HCT. We searched for matched sibling (n=16) followed by matched (n=10) or mismatched (n=5) unrelated and familial mismatched donors (n=4). Preconditioning regimen consisted of fludarabine (total 150 mg/m²) and busulfan (total 6.4 mg/kg) with total body irradiation≤ 400cGy. All showed engraftments, but four (11.4%) showed either leukemic relapse (n=3) or delayed graft failure (n=1). Two-year overall survival (OS) and non-relapse mortality (NRM) was 60.0% and 29.9%, respectively. Acute GVHD was observed in 19 patients, and grade III-IV acute GVHD was higher with HLA-mismatch (70% vs. 20%, p=0.008). Significant hepatic GVHD was observed in nine patients (5 acute, 4 chronic), and six of them died. Multivariate analysis revealed inferior OS with HLA-mismatch (HR=6.40, 95%CI 1.6-25.7, p=0.009) and in patients with high ferritin level at post-HCT D+21 (HR=7.22, 95%CI 1.9-27.5, p=0.004), which were related to hepatic GVHD and high NRM. RIC allo-HCT can be a valid choice for advanced MF. However, HLA-mismatch and high post-HCT ferritin levels related to significant hepatic GVHD should be regarded as poor-risk parameters.