611 - Haploidentical Stem Cell Rescue in Children with Primary Graft Failure Following Umbilical Cord Blood Transplant

Abstract

Background: The use of UCBT has become a suitable alternative source for haematopoietic stem cell transplant (HSCT), allowed access to transplantation, specially in children. In Colombia, there is not an unrelated donor registry so the umbilical cord blood is the alternative election in our center because rapid donor availability, permissive partial HLA matching and low incidence of graft versus host disease (GVHD). UCBT outcomes have significantly improved in the last decades however, a fraction of recipients develop graft failure and are candidates for a second transplant. In those cases, a second transplant using an haploidentical donor have been the election for our center. Methods: We conducted a retrospective analysis of all pediatric patients (<18 years) undergoing UCBT at HOMI between august 2013 and august 2017 who subsequently received a second HSCT due to primary graft failure (n = 10). Kaplan-Meier estimates of overall survival (OS), engraftment and GVHD incidence were calculated. All received rabbit ATG (2 mg/kilo) as the only conditioning régimen for the second transplant. Results: The OS at 100 days and 1 year was 50%. Median time to neutrophil (ANC 500) and platelet (50K) engraftments were 18 (range, 12-41) and 57 days (range12-210) respectively. The incidence of grades II-IV acute GVHD was 30%. Severe chronic GVHD was seen in 1 patient (10%). Conclusion: Haploidentical stem cell rescue resulted in acceptable survival in children with primary graft failure post UCBT. For our center, the haploidentical donor allows quick second transplant with short period of cytopenias and aceptable incidence of GVHD.