Outpatient Management of Patients Conditioned with Fludarabine and Treosulfan prior to Allogeneic Hematopoietic Cell Transplantation.

Allogenic hematopoietic cell transplantation (allo-HCT) with myeloablative conditioning traditionally requires 30 days of hospitalization after stem cell infusion. However, advancements in supportive and prophylactic care have allowed for a trend toward outpatient management of allo-HCT, potentially leading to improved patient quality of life and increased cost-effectiveness of the procedure. In 2014, fludarabine and treosulfan (FluTreo) conditioning was introduced as a myeloablative regimen with reduced toxicity at Copenhagen University Hospital, Rigshospitalet (CUH). After gaining experience with the regimen, an outpatient program was established. Here we share the outcomes of outpatient conditioning with FluTreo allo-HCT at CUH. This study was conducted to investigate the safety and feasibility of outpatient FluTreo allo-HCT, as well as to investigate the potentially improved cost-effectiveness of outpatient allo-HCT primarily through a reduction in hospital length of stay compared to the 30 days of hospitalization associated with standard myeloablative conditioning. This retrospective study included all patients undergoing FluTreo allo-HCT due to malignant diseases (n = 124) at CUH between 2018 and 2022. Patients received outpatient treatment (n = 91) unless certain circumstances necessitated planned hospitalization (n = 33). As conditioning, patients received i.v. fludarabine 90 mg/m and treosulfan either 30 or 42 g/m. Statistical analyses included descriptive statistics and Kaplan-Meier survival analysis. The median duration of hospitalization in the outpatient group was 4 days (interquartile range [IQR], 0 to 12.5 days) from day -6 to day +28 compared to a median of 28 days (IQR, 26 to 34 days) in the inpatient group. Thirty-two patients (35%) in the outpatient group did not require hospitalization before day +28 post-transplantation. The remaining 59 patients (65%) were hospitalized after a median of 12 days (IQR, 7 to 16 days) from the start of conditioning, with a median stay of 10 days (IQR, 5 to 18 days). The outpatient group required significantly less i.v. antibiotics, i.v. opioids, and parenteral nutrition compared to the inpatient group, despite no differences in treatment toxicity, acute graft-versus-host disease, or relapse between the groups. The outpatient group experienced no early deaths during the first 3 months after transplantation, and 1-year nonrelapse mortality was 6%. Outpatient allo-HCT with FluTreo conditioning is feasible and safe in a selected group of patients, significantly reducing hospitalization days without compromising patient outcomes. Outpatient FluTreo allo-HCT potentially provides a more cost-effective and patient-friendly alternative compared to traditional in-patient management.