Treosulfan-Based Conditioning Regimen In Pediatric Hematopoietic Stem Cell Transplantation: A Retrospective Analysis on Behalf of the Spanish Group for Hematopoietic Transplantation and Cellular Therapy (GETH-TC)

Abstract

Data on treosulfan-based conditioning regimens are little by little increasing, and the benefits of this approach are consistent, particularly regarding acute toxicity. This study aims to describe the results of treosulfan-based conditioning regimens in children, focusing on toxicity and outcomes when used to treat both malignant and non-malignant diseases. Retrospective observational study on pediatric patients treated in Spain with treosulfan-based conditioning regimens before hematopoietic stem cell transplantation (HSCT), based on data collection from electronic clinical records. One hundred and sixty treosulfan-based conditioning HSCTs to treat non-malignant diseases (n=117) or malignant diseases (n=43) in 158 children and adolescents are reported. Median age at HSCT was 5.1 years (IQR: 2-10). The most frequent diagnoses were primary immunodeficiency (n=42; 36%) and sickle cell disease (n=42; 36%) in the non-malignant cohort and acute lymphoblastic leukemia (n=15; 35%) in the malignant cohort. Engraftment occurred in 97% of the patients. There was a longer median time to neutrophil engraftment (17 vs. 14 days; p=0.008) and platelet engraftment (20 vs. 15 days; p=0.002) in the non-malignant cohort. The 1-year cumulative incidence of VOD was 7.98 (95%CI [4.6-13.6]), with no significant differences between cohorts. The 1-year cumulative incidence of grade III-IV aGvHD was higher in the malignant cohort (18% vs. 3.2%; p=0.011). Overall, cGvHD was more frequently observed in the malignant cohort for both total incidence (9 vs. 3%; p<0.001) and 2-year cumulative incidence of total cGvHD (16 vs. 1.9%; p<0.001). The 2-year cumulative TRM was 15%, with no differences between cohorts. 5-year Overall Survival was 80% (95%CI [72-86]) and was higher in the non-malignant cohort (87 vs. 61%; p=0.01). The 2-year cumulative incidence of relapse in the malignant cohort was 25%. 5-year cumulative GRFS rate was 60% (95%CI [51-70]) and was higher in the non-malignant cohort (72 vs. 22%; p<0.001). The treosulfan-based radiation-free conditioning regimen is feasible, achieving a high engraftment rate and 5-year overall survival. A treosulfan-based conditioning regimen is an emerging option for the first HSCT in non-malignant diseases.