Researchers conducted a phase 2 study to determine if treatment with posttransplant cyclophosphamide (PTCy) is safe for patients with hematologic malignancies in the human leukocyte antigen (HLA)-haploidentical setting. Study results were presented at the Society of Hematologic Oncology (SOHO) 2021 Annual Meeting by Rohtesh S. Mehta, MD, MPH, MS, of The University of Texas MD Anderson Cancer Center in Houston, TX, and colleagues.
The study was an open-label, nonrandomized trial including patients who had any hematologic malignancy and received a hematopoietic stem cell transplant (HCT) involving an HLA-matched or -haploidentical donor. Prior to stem cell infusion, busulfan, thiotepa, and fludarabine were given. Following stem cell infusion, patients received PTCy and tacrolimus with or without mycophenolate mofetil for graft vs host disease (GVHD) prophylaxis. The primary study objectives were day 100 nonrelapse mortality (NRM) and the rate of adverse events (AEs) of grade 3 or higher. Numerous secondary and exploratory analyses were also conducted.
A total of 55 patients were evaluated, and their median age was 47 years (range, 15-65). Slightly over half the patients (54.5%) had an acute myeloid leukemia/myelodysplastic syndrome diagnosis. Of the total patient population, nearly half of patients (47.3%) had a haploidentical donor.
The day 100 NRM rate was 16.4% (95% CI, 6.5%-26.3%). The cumulative incidence of NRM at 1 year was 20%, and at 2 years it was 21.8%. The 2-year cumulative incidence of relapse was 23.6%, for overall survival it was 65.5%, and for GVHD- or relapse-free survival it was 43.6%.
The rate of grade 3 or higher AEs was 87% of the population, or 47 patients. Grade 3 culture-negative neutropenic fever was the most common AE, reported in 32 patients and at a median of 3 days after HCT. There were 30 events of infection, of which 15 were bacterial and 14 were viral. A total of 21 deaths occurred. Most commonly these were associated with relapse in 8 patients, acute GVHD in 4 patients, and infection in 6 patients. The day 100 rate of acute GVHD of grades 2 to 4 was 38.2% of patients, and for grades 3 to 4 it was 9.1%. Chronic GVHD at 2 years was reported in 10.9% of patients.
Graft failure was reported to not occur in any patient, and neutrophil engraftment occurred at a median time of 17 days (range, 13-39). The median time to platelet engraftment at a level of ≥20 K/mL was 25 days (range, 11-167), and this occurred in 49 patients. The median time to platelet engraftment at a level of ≥50 K/mL was 32 days (range, 15-296), and this was reported in 42 patients.
The research team concluded that the use of PTCy in this study was well tolerated and imparted a low risk of NRM and either acute or chronic GVHD. They considered this study’s results to be promising and indicated that research is ongoing.
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Mehta RS, Bassett R, Olson A, et al. Post-transplant cyclophosphamide in HLA matched and haploidentical transplant recipients receiving myeloablative fractionated busulfan conditioning regimen: results of a phase II study. Paper presented at: Annual Meeting of the Society of Hematologic Oncology (SOHO); September 8-11, 2021. Abstract CT-046.
This article originally appeared on Hematology Advisor