Long-term outcome and chimerism in patients with Wiskott–Aldrich syndrome treated by hematopoietic cell transplantation: a retrospective nationwide survey

We analyzed the outcomes of allogeneic stem cell transplantation (SCT) and risk factors for chimerism in 108 patients with Wiskott–Aldrich syndrome (WAS) who were registered with The Japan Society for Hematopoietic Cell Transplantation between January 1985 and December 2016. A preparative conditioning regimen consisting of myeloablative conditioning (MAC) was provided to 76 patients, and reduced-intensity conditioning was provided to 30 patients. Fifty-one patients received prophylaxis against graft-versus-host disease (GVHD) with cyclosporine, and 51 patients received tacrolimus (Tac). Chimerism analyses had been performed in 91 patients. Neutrophil engraftment was achieved in 91 patients (84.3%). The engraftment rate was significantly higher in patients who received Tac for GVHD prophylaxis (p = 0.028). Overall survival rate (OS) was significantly higher in patients with complete chimerism than in patients with mixed chimerism (88.2 ± 6.1% and 66.7 ± 9.9%, respectively, p = 0.003). Multivariate analysis showed that the rate of complete chimerism in patients who received MAC including cyclophosphamide (CY) at a dose of 200 mg/kg was significantly higher (p = 0.021) than that in patients who received other conditioning. Thus, MAC including CY at a dose of 200 mg/kg and Tac for GVHD prophylaxis were optimal conditions of SCT for patients with WAS under existing study.