Use Of Post Transplant Cyclophosphamide In Matched Related And Unrelated Donor Hematopoietic Stem Cell Transplant For Benign Hematological Disorders

Background: Introduction of Post-Transplant Cyclophosphamide (PTCy) based immunosuppression in Haploidentical Hematopoietic Stem Cell Transplants (HSCT) has shown to reduce the incidence of Graft vs Host Disease (GVHD). However, data on its use in HLA matched settings is lacking. Here we describe our experience using PTCY in pediatric patients undergoing HSCT for the same. Methods: We retrospectively analysed data of 16 pediatric patients who underwent HLA matched HSCT using PTCy from March 2022 to November 2023 at our institute. Results: Sixteen patients of median age-6 years (Range: 1 to 17 years) were analysed. Male: female ratio was 3.3:1. Indications of transplant were Thalassemia major in 10, severe aplastic anemia in 5 and Congenital dyserythropoietic anemia type II in 1. Conditioning regimes used were Rabbit ATG-Thio-Flu-Cy-2Gy TBI in 8 and Rabbit ATG-Thio-Treo-Flu-2Gy TBI in 3 which was preceded by two cycles of pre-transplant immunosuppression (PTIS); Rabbit ATG-Flu-Cy-4Gy TBI in 5 patients. Median CD34 dose was 5.1 million/kg (Range: 4.7 to 5.6 million/kg). PTCy (50 mg/kg on d+3, +4), Mycophenolate mofetil and cyclosporine were used as GVHD prophylaxis. Fifteen patients had neutrophil enlargement at median 16 days (Range:11- 21 days). One patient had primary and one had secondary graft failure. Cytomegalovirus reactivation was seen in 8 patients. Of the 14 evaluable patients, 3 patients had grade I-II acute GVHD at median 32 days post HSCT (Range: 28-140days). None of the patients had chronic GVHD. Median follow up duration post HSCT was 473 days (Range: 85-808 days). Event free and overall survival rates were 81.25% and 93.7% respectively. Conclusion: PTCy based approach appears to be promising in matched related and unrelated donor transplants for benign hematological disorders.