Acute toxicity and outcome among pediatric allogeneic hematopoietic transplant patients conditioned with treosulfan-based regimens

Treosulfan vs busulfan conditioning for allogeneic bmt in children with nonmalignant disease: a randomized phase 2 trial

Optimal conditioning prior to allogeneic hematopoietic stem cell transplantation for children with non-malignant diseases is subject of ongoing research. This prospective, randomized, phase 2 trial compared safety and efficacy of busulfan with treosulfan based preparative regimens. Children with non-malignant diseases received fludarabine and either intravenous (IV) busulfan (4.8 to 3.2 mg/kg/day) or IV treosulfan (10, 12, or 14 g/m2/day). Thiotepa administration (2 × 5 mg/kg) was at the investigator's discretion. Primary endpoint was freedom from transplantation (treatment)-related mortality (freedom from TRM), defined as death between Days -7 and +100. Overall, 101 patients (busulfan 50, treosulfan 51) with at least 12 months follow-up were analyzed. Freedom from TRM was 90.0% (95% CI: 78.2%, 96.7%) after busulfan and 100.0% (95% CI: 93.0%, 100.0%) after treosulfan. Secondary outcomes (transplantation-related mortality [12.0% versus 3.9%]) and overall survival (88.0% versus 96.1%) favored treosulfan. Graft failure was more common after treosulfan (n = 11), than after busulfan (n = 2) while all patients were rescued by second procedures except one busulfan patient. CTCAE Grade III adverse events were similar in both groups. This study confirmed treosulfan to be an excellent alternative to busulfan and can be safely used for conditioning treatment in children with non-malignant disease.

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)

Increasing data on treosulfan-based conditioning regimens before hematopoietic stem cell transplantation (HSCT) demonstrate the consistent benefits of this approach, particularly regarding acute toxicity. This study aimed to describe the results of treosulfan-based conditioning regimens in children, focusing on toxicity and outcomes when used to treat both malignant and nonmalignant diseases. This retrospective observational study of pediatric patients treated in Spain with treosulfan-based conditioning regimens before HSCT was based on data collection from electronic clinical records. We studied a total of 160 treosulfan-based conditioning HSCTs to treat nonmalignant diseases (n = 117) or malignant diseases (n = 43) in 158 children and adolescents. The median patient age at HSCT was 5.1 years (interquartile range, 2 to 10 years). The most frequent diagnoses were primary immunodeficiency (n = 42; 36%) and sickle cell disease (n = 42; 36%) in the nonmalignant disease cohort and acute lymphoblastic leukemia (n = 15; 35%) in the malignant disease cohort. Engraftment occurred in 97% of the patients. The median times to neutrophil engraftment (17 days versus 14 days; P = .008) and platelet engraftment (20 days versus 15 days; P = .002) were linger in the nonmalignant cohort. The 1-year cumulative incidence of veno-occlusive disease was 7.98% (95% confidence interval [CI], 4.6% to 13.6%), with no significant differences between cohorts. The 1-year cumulative incidence of grade III-IV acute graft-versus-host disease (GVHD) was higher in the malignant disease cohort (18% versus 3.2%; P = .011). Overall, the malignant cohort had both a higher total incidence (9% versus 3%; P < .001) and a higher 2-year cumulative incidence (16% versus 1.9%; P < .001) of total chronic GVHD. The 2-year cumulative transplantation-related mortality was 15%, with no difference between the 2 cohorts. The 5-year overall survival was 80% (95% CI, 72% to 86%) and was higher in the nonmalignant cohort (87% versus 61%; P = .01). The 2-year cumulative incidence of relapse was 25% in the malignant cohort. The 5-year cumulative GVHD-free, relapse-free survival rate was 60% (95% CI, 51% to 70%) and was higher in the nonmalignant cohort (72% versus 22%; P < .001). A treosulfan-based radiation-free conditioning regimen is feasible, achieving a high engraftment rate and 5-year overall survival, and is an emerging option for the first HSCT in nonmalignant diseases.

Treosulfan Versus Busulfan-based Conditioning in Pediatric Patients Undergoing Hematopoietic Stem Cell Transplantation: A Systematic Review and Meta-analysis

It is unclear whether there is a difference in outcomes with treosulfan or busulfan-based conditioning in pediatric patients undergoing hematopoietic stem cell transplantation (HSCT). We reviewed the evidence on this topic through a systematic review and meta-analysis, the comparison between treosulfan and busulfan-based conditioning in pediatric patients undergoing HSCT for instance. Six studies were included. Meta-analysis showed that there was no difference in the incidence of acute graft versus host disease (odds ratio [OR]: 0.96; 95% CI: 0.57, 1.61), grade II to IV acute graft versus host disease (OR: 1.19; 95% CI: 0.83, 1.72), chronic GVHD (OR: 1.18; 95% CI: 0.70, 2.00), and veno-occlusive disease (OR: 0.92; 95% CI: 0.22, 3.85) between treosulfan and busulfan groups. Pooled analysis indicated marginally better survival with treosulfan-based conditioning (OR: 1.57; 95% CI: 1.00, 2.44), however, these results were unstable on sensitivity analysis. A meta-analysis found no difference in transplant-related mortality (OR: 0.70; 95% CI: 0.34, 1.42) between the two groups. Retrospective data from a heterogenous population indicates that there is no difference in the rate of GVHD after treosulfan versus busulfan-based conditioning for pediatric HSCT. A marginal improvement in survival was noted with treosulfan but the results remained unstable. Future randomized controlled trials are needed to provide better evidence.

Transplant for non-malignant disorders: an International Society for Cell & Gene Therapy Stem Cell Engineering Committee report on the role of alternative donors, stem cell sources and graft engineering

Hematopoietic stem cell transplantation (HSCT) is curative for many non-malignant disorders. As HSCT and supportive care technologies improve, this life-saving treatment may be offered to more and more patients. With the development of new preparative regimens, expanded alternative donor availability, and graft manipulation techniques, there are many options when choosing the best regimen for patients. Herein the authors review transplant considerations, transplant goals, conditioning regimens, donor choice, and graft manipulation strategies for patients with non-malignant disorders undergoing HSCT.

A retrospective study of treosulfan versus busulfan-based conditioning in pediatric patients

OBJECTIVES

To compare the outcomes of treosulfan-based vs. busulfan-based conditioning regimens in allogeneic hematopoietic stem cell transplantation (HSCT) in pediatric patients.

METHODS

Retrospective study of all consecutive patients (2012-2019) treated with allogenic HSCT and treosulfan- or busulfan-based conditioning regimens at a single center.

RESULTS

A total of 101 HSCT were included: 66 HSCT with busulfan and 35 with treosulfan. In malignant diseases (n=62), busulfan-based conditioning was more commonly employed than treosulfan: 82.3% vs. 17.7%. However, the use of treosulfan for malignant diseases increased over time: 6.5% of HSCT in 2012-2015 vs. 29% of HSCT in 2015-2019 (P=0.02). The cohort of treosulfan had more children under 1-year of age than the busulfan cohort (31 vs. 13%; P=0.033). The percentage of patients who received serotherapy was 73 and 89% in the non-malignant and malignant groups respectively. The engraftment, time to neutrophil, and platelet engraftment were not significantly different between the busulfan and the treosulfan cohorts. Rate of grade II-IV acute GvHD was significantly higher in the busulfan cohort than the treosulfan cohort (39% vs. 15%; P=0.016). No differences were observed in endothelial damage complications, chronic GvHD, relapse, overall survival, and transplant-related mortality.

CONCLUSIONS

Busulfan-based conditioning regimens are used more frequently for children undergoing allogenic HSCT, but treosulfan-based conditioning is gaining acceptance. Treosulfan-based conditioning is associated with lower rates of acute GvHD, and no significant differences on overall survival were observed compared with busulfan.

Considerations in Preparative Regimen Selection to Minimize Rejection in Pediatric Hematopoietic Transplantation in Non-Malignant Diseases

The variables that influence the selection of a preparative regimen for a pediatric hematopoietic stem cell transplant procedure encompasses many issues. When one considers this procedure for non-malignant diseases, components in a preparative regimen that were historically developed to reduce malignant tumor burden may be unnecessary. The primary goal of the procedure in this instance becomes engraftment with the establishment of normal hematopoiesis and a normal immune system. Overcoming rejection becomes the primary priority, but pursuit of this goal cannot neglect organ toxicity, or post-transplant morbidity such as graft-versus-host disease or life threatening infections. With the improvements in supportive care, newborn screening techniques for early disease detection, and the expansion of viable donor sources, we have reached a stage where hematopoietic stem cell transplantation can be considered for virtually any patient with a hematopoietic based disease. Advancing preparative regiments that minimize rejection and transplant related toxicity will thus dictate to what extent this medical technology is fully utilized. This mini-review will provide an overview of the origins of conditioning regimens for transplantation and how agents and techniques have evolved to make hematopoietic stem cell transplantation a viable option for children with non-malignant diseases of the hematopoietic system. We will summarize the current state of this facet of the transplant procedure and describe the considerations that come into play in selecting a particular preparative regimen. Decisions within this realm must tailor the treatment to the primary disease condition to ideally achieve an optimal outcome. Finally, we will project forward where advances are needed to overcome the persistent engraftment obstacles that currently limit the utilization of transplantation for haematopoietically based diseases in children.