Haploidentical hematopoietic stem cell transplantation with post-transplant cyclophosphamide for Fanconi anemia with/without anti-thymocyte globulin.

Background: We present comparative data of children with Fanconi anemia undergoing haploidentical hematopoietic stem cell transplantation (HSCT) with or without the addition of rabbit anti-thymocyte globulin (r-ATG) to the conditioning regimen.

Patients And Methods: This retrospective study included children with Fanconi anemia aged up to 18 years who underwent haploidentical HSCT between January 2015 and December 2022. The children were included in two cohorts in this study. Cohort 1 included children who received conditioning with fludarabine/cyclophosphamide/single fraction of 2 Gy TBI. The children in cohort 2 received the same conditioning along with r-ATG. Post-transplant cyclophosphamide was administered at a dose of 25 mg/kg on day3 and day4 in both cohorts.

Results: A total of 35 children were included in the study, 25 in cohort 1 and 10 in cohort 2. Neutrophil engraftment was documented around day 14-16 post infusion in 21 children (84%) in cohort 1 and in 8 children (80%) in cohort 2. There was a significant difference in the incidence of the severity of graft versus host disease (GVHD) between the two cohorts ( = 0.003). In cohort 1, acute GVHD was documented in 17 children (68%), with grade 1/2 skin GVHD in 10 children, and grade 3/4 skin and gut GVHD in 7 children. Grade 4 gut GVHD was the cause of death in three children in cohort 1. In cohort 2, acute GVHD was documented in one child (10%) who had grade 4 skin and gut GVHD and succumbed to the above. Chronic GVHD was noted in nine (36%) children in cohort 1, and in one child (10%) in cohort 2. Cytomegalovirus reactivation was documented in 11 children (44%) in cohort 1 and three children (30%) in cohort 2. Overall survival was found to be 16/25 (64%) in cohort 1, with a median follow-up of 49 months, and 7/10 (70%) in cohort 2, with a median follow-up of 12 months.

Conclusion: Serotherapy with r-ATG significantly reduced the incidence of GVHD from 68% to 10% in children with Fanconi anemia, with an increase in overall survival from 64% to 70%, although it did not affect graft failure. Further studies should focus on decreasing graft failure rates with early HSCT before multiple transfusions.