Excellent outcomes following hematopoietic cell transplantation for Wiskott-Aldrich syndrome: a PIDTC report

Abstract

Wiskott-Aldrich syndrome (WAS) is an X-linked disease caused by mutations in the WAS gene leading to thrombocytopenia, eczema, recurrent infections, autoimmune disease, and malignancy. Hematopoietic cell transplantation (HCT) is the primary curative approach, with the goal of correcting the underlying immunodeficiency and thrombocytopenia. HCT outcomes have improved over time, particularly for patients with HLA-matched sibling and unrelated donors. Here we report the outcomes of 129 patients with WAS who underwent HCT at 29 Primary Immune Deficiency Treatment Consortium centers between 2005 and 2015. Median age at HCT was 1.2 years. Most patients (65%) received myeloablative busulfan-based conditioning. With a median follow-up of 4.5 years, the 5-year overall survival (OS) was 91%. Superior 5-year OS was observed in patients <5 vs. ≥5 years old at the time of HCT (94% vs. 66%, overall p=0.0008). OS was excellent regardless of donor type even in cord blood recipients (90%). Conditioning intensity did not impact OS, but was associated with donor T-cell and myeloid engraftment post-HCT. Specifically, patients who received fludarabine/melphalan-based reduced-intensity regimens were more likely to have donor myeloid chimerism 95%) versus low-level (5%-49%) donor myeloid engraftment. In summary, HCT outcomes for WAS have improved since 2005 compared to prior reports. HCT at a younger age continues to be associated with superior outcomes supporting the recommendation for early HCT. High-level donor myeloid engraftment is important for platelet reconstitution following either myeloablative or busulfan-containing reduced intensity conditioning. (www.clinicaltrials.gov NCT02064933.)