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.