Irradiation-free RIC HSCT has a tolerable safety profile and is effective therapy for pediatric bone marrow failure...

For patients with bone marrow failure syndromes (BMFS) who may tolerate gradual donor engraftment and achieve adequate disease control with stable mixed chimerism, RIC regimens may be preferable to myeloablative regimens. We performed a retrospective analysis of outcomes for patients who underwent HSCT at our institution between 2009 and 2017 for BMFS using an irradiation-free RIC regimen. Fourteen pediatric patients with BMFS received fludarabine (30 mg/m² IV daily × 3), thiotepa (5 mg/kg IV every 12 hours × 2), and melphalan (70 mg/m² IV daily × 2) prior to HSCT. Our cohort included the following diagnoses: SAA (n = 7), CAMT (n = 4), SCN (n = 1), DBA (n = 1), and non-Fanconi congenital BMF (n = 1). Seven patients underwent a MSD transplant; seven underwent an unrelated donor transplant. All patients are alive with median follow-up of 1112 days (range 455-2549 days). The median time to neutrophil engraftment was 16 days (range 10-26 days). All were transfusion independent by day + 100. The highest grade of aGVHD was grade 2; 8 (57%) did not develop aGVHD. Four (28.5%) developed extensive cGVHD, 4 (28.5%) developed limited cGVHD, and 6 (43%) did not develop cGVHD. No patients developed SOS. None died from GVHD or infectious complications. HSCT with RIC with fludarabine, thiotepa, and melphalan for BMFS was effective with a tolerable safety profile. Probability of OS at 100 days and 1 year was 100%.