Effect of CD34+ Cell Dose on the Outcomes of Allogeneic Stem Cell Transplantation with Post-Transplantation Cyclophosphamide

G-CSF-Primed Peripheral Blood Stem Cell Haploidentical Transplantation Could Achieve Satisfactory Clinical Outcomes for Severe Aplastic Anemia Patients

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) continues to be a cornerstone in the treatment of severe aplastic anemia (SAA). The advancement of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) has broadened therapeutic possibilities, particularly for patients lacking fully HLA-matched donors. However, it still remains unclear which type of graft source is better for SAA patients underwent haplo-HSCT.

OBJECTIVES

This study aimed to assess the clinical outcomes of haplo-HSCT using granulocyte colony-stimulating factor (G-CSF)-primed peripheral blood (G-PB) as the graft source, comparing them to a control group receiving G-CSF-primed bone marrow (BM) plus G-PB (BM + PB).

STUDY DESIGN

This was a single-center, retrospective, case-pair cohort study. Between January 2020 and December 2023, a total of 278 consecutive SAA patients received haplo-HSCT in Peking University People's hospital. In total, 22 patients receiving haplo-HSCT using PB were included in this study. To minimize the impact of potential confounders in this study, we used the propensity score matching (PSM) method to match patients who underwent haplo-HSCT with G-PB plus G-BM in the same time with a 3:1 ratio using nearest neighbor matching. In the end, 88 patients were included in this study. 22 patients received PB stem cells as graft, while 66 patients received G-CSF-primed BM plus PB as graft.

RESULTS

The PB group demonstrated greater neutrophil (100% vs. 93.9%, p=0.04) and platelet engraftment (95.5% vs. 89.0%, p=0.03) incidence compared to the BM + PB group. There were no significant differences in the cumulative incidences of grade II-IV (13.6% vs. 25.8%, p = 0.28) or grade III-IV acute graft-versus-host disease (aGVHD) (4.5% vs. 4.6%, p = 0.99) between the PB group and BM+PB group. The PB group (36.7%) exhibited a trend toward a higher incidence of chronic GVHD compared to BM+PB group (24.1%); however, the difference between the two groups was not statistically significant. Moreover, the immune reconstitution of CD3+T cells, CD4+T cells, CD8+T cells and CD19+B cells were also comparable between two groups. At three years post haplo-HSCT, the probabilities of overall survival (OS), failure-free survival (FFS) and GVHD-free/failure-free survival (GFFS) were 86.1% versus 87.9% (p = 0.90), 86.1% versus 83.3% (p = 0.73) and 76.5% versus 75.2% (p = 0.70) for PB and BM + PB group, respectively. In univariate analysis, graft source did not influence the clinical outcomes after HSCT.

CONCLUSIONS

This study illustrated the safety and efficacy of haplo-HSCT with PB as single graft source as the treatment for SAA, providing a basis for further potential optimization of the current protocol. In the future, this conclusion should be further tested by prospective randomized trails.

Donor selection in T-cell-replete haploidentical donor peripheral blood stem cell transplantation

The effects of donor characteristics on outcomes after T-cell-replete (TCR) haploidentical donor peripheral blood stem cell transplantation (PBSCT) with post-transplant cyclophosphamide (PTCy) or low-dose antithymocyte globulin (ATG) remain unclear. We evaluated the impact in 1,677 patients who received a PTCy protocol (PTCy-haplo; n = 1,107) or low-dose ATG protocol (ATG-haplo; n = 570). A low CD34+ cell dose (<4 ×106/kg) was the only donor characteristic associated with worse overall survival (OS) after PTCy-haplo (adjusted hazard ratios [aHR] = 1.49, P = 0.008), whereas increasing donor age by decade (aHR = 1.12, P = 0.008) and human leukocyte antigen 2-3 antigen mismatches (aHR = 1.46, P = 0.010), compared to HLA 0-1 antigen mismatches, were associated with worse OS after ATG-haplo. Increasing donor age was associated with a high risk of grade III-IV acute GVHD both after PTCy-haplo (HR: 1.32, P = 0.009) and ATG-haplo (HR: 1.22, P = 0.006). Offspring donors had better relapse-free survival and GVHD-free relapse-free survival than sibling donors after ATG-haplo. Our data highlights the donor characteristics associated with improved transplant outcomes after TCR haploidentical donor PBSCT with PTCy or low-dose ATG.

Comparative outcomes of various transplantation platforms, highlighting haploidentical transplants with post-transplantation cyclophosphamide for adult T-cell leukaemia/lymphoma

This study retrospectively compared outcomes of various allogeneic haematopoietic cell transplantation (allo-HCT) platforms in patients with adult T-cell leukaemia/lymphoma. Platforms included human leukocyte antigen (HLA)-haploidentical-related donors using post-transplant cyclophosphamide (PTCY), HLA-matched related donors (MRD), HLA-matched unrelated donors (MUD) and cord blood transplantation (CBT). Patients who underwent their first allo-HCT between 2016 and 2021 were included. Outcomes analysed were overall survival (OS), relapse and non-relapse mortality (NRM). Seven hundred patients were included (PTCY, n = 121; MRD, n = 91; MUD, n = 160; CBT, n = 328). With a median follow-up of 794 days for survivors, 2-year OS was 48.1% (PTCY), 48.8% (MRD), 48.4% (MUD) and 34.6% (CBT); the respective 2-year cumulative incidence of relapse was 37.1%, 47.5%, 33.9% and 45.1% and that of NRM was 24.2%, 19.8%, 24.7% and 27.3%. PTCY was associated with delayed platelet engraftment relative to MRD and MUD. There was no increase in the incidence of severe acute or chronic graft-versus-host disease. In the PTCY group, poor performance status was a significant predictor of inferior OS, and infused CD34+ cell numbers of less than 5 × 106/kg were associated with delayed neutrophil and platelet engraftment. These results suggest that allo-HCT with PTCY is a safe and effective platform for patients with adult T-cell leukaemia/lymphoma.

Treosulfan- Versus Busulfan-based Conditioning in Allogeneic Hematopoietic Cell Transplantation for Myelodysplastic Syndrome: A Single-center Retrospective Propensity Score-matched Cohort Study

Treosulfan has shown promise in allogeneic hematopoietic cell transplantation (HCT) for its myeloablative properties and low toxicity. In this single-center retrospective propensity score-matched cohort study we compared treosulfan- and busulfan-based conditioning in allogeneic HCT for patients with myelodysplastic syndrome (MDS). This study included 138 adults who underwent allogeneic HCT for MDS or chronic myelomonocytic leukemia at Princess Margaret Hospital, Toronto, from 2015 to 2022. Using propensity score matching, we compared transplant outcomes between 2 well-matched cohorts who received conditioning with either fludarabine-treosulfan (FT) (n = 46) or fludarabine-busulfan with total body irradiation (FBT200) (n = 92). A scoring system based on patient age, Karnofsky performance score, and hematopoietic cell transplant comorbidity index was used to assign patients based on fitness to low-dose (30 g/m2) or high-dose (42 g/m2) treosulfan: 32 (69.6%) received high-dose treosulfan. The racial composition of the 2 groups was similar, with 27.2% and 21.7% of FBT200 and FT recipients, respectively, identifying as non-Caucasian (P = .61). Primary outcomes were analyzed at a median follow-up of 747 days. Of all participants, 116 (84.0%) received graft-versus-host disease (GVHD) prophylaxis with post-transplant cyclophosphamide (PTCY) and antithymocyte globulin (ATG). Patients who received FT had a superior 2-year overall survival (OS) compared to those who received FBT200: 66.9% (95% confidence interval (CI): 46.1 to 81.2) versus 44.5% (95% CI: 34 to 54.4), hazard ratio (HR): 0.43, 95% CI: 0.22 to 0.84 (P = .013). In multivariate analysis (MVA), only the use of fresh grafts (P = .02) and FT (P = .01) were associated with improved OS. FT was associated with superior 2-year relapse-free survival (RFS) compared to FBT200: 63.1% (95% CI: 42.6 to 77.9) versus 39.1% (95% CI: 29.1 to 49.1), HR: 0.44 (95% CI: 0.24 to 0.81), P = .008. In MVA, the use of fresh grafts (P = .03) and FT (P = .009) were associated with improved RFS. Recipients of FT demonstrated superior 2-year graft-versus-host disease relapse-free survival (GRFS) compared to those who received FBT200: 57.4% (95% CI: 37.8 to 72.8) versus 35.1% (95% CI: 25.5 to 45). In MVA, only FT was associated with superior GRFS (P = .02). FT recipients exhibited markedly superior 1-year event-free survival compared to recipients of FBT200 in univariate analysis (40.3% (95% CI: 25.9 to 54.2) versus 9.2% (95% CI: 4.4 to 16.3), HR: 0.47 (95% CI: 0.30 to 0.72), P < .001) and MVA (P = .004). FT was associated with lower 1-year nonrelapse mortality compared to FBT200 in univariate analysis (9.9% (95% CI: 3.0 to 21.8) versus 29.7% (95% CI: 20.6 to 39.3), HR: 0.41 (95% CI: 0.17 to 0.96), P = .04) and MVA (P = .04). Our study utilized propensity score matching to demonstrate superiority of treosulfan- over busulfan-based conditioning in stem cell transplantation of patients with MDS and is the first to evaluate the performance of treosulfan-based conditioning in combination with ATG and PTCY. As such, it contributes to the increasing body of evidence supporting the safety of treosulfan, even at the dose of 42 g/m2.

Graft Failure Incidence, Risk Factors, and Outcomes in Patients Undergoing Non-Myeloablative Allogeneic Hematopoietic Cell Transplantation Using Post-Transplant Cyclophosphamide

Graft failure (GF) is a major complication of allogeneic hematopoietic cell transplantation (alloHCT) that results in significant morbidity and mortality. Post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis has emerged as an effective regimen across the spectrum of donor-match settings, but few studies have investigated the characteristics of GF in the setting of PTCy-based GVHD prophylaxis. The objective was to detail the incidence, clinical features, risk factors, and outcomes for patients with primary graft failure (PGF) and secondary graft failure (SGF). In this retrospective study at a single institution, 958 consecutive patients undergoing first nonmyeloablative (NMA) alloHCT with PTCy-based GVHD prophylaxis were analyzed. PGF was defined as a failure to achieve an ANC ≥ 500 cells/m3 by day 30 of transplant in the absence of residual disease. SGF was defined as complete loss of donor chimerism after initial engraftment. The incidences of PGF and SGF were 3.8% (n = 37) and 1.8% (n = 17), respectively. Neither PGF nor SGF were associated with HLA disparity. In a multivariate analysis, risk factors for PGF in this cohort included age ≥ 65 (OR 2.4, 95% CI 1.2 to 4.8, P = .0120), an underlying diagnosis of MDS, MPN, or MDS/MPN overlap (OR 2.8, 95% CI 1.4 to 5.7, P = .0050), post-transplant viremia with HHV-6 (OR 2.9, 95% CI 1.5 to 5.7, P = .0030), and low CD34+ dose (OR 0.7, 95% CI 0.5 to 0.9, P = .0080). Patients with PGF had poor overall survival, driven primarily by a high rate of nonrelapse mortality (59% at 36 months). SGF was associated with use of a bone marrow graft source and a diagnosis of Hodgkin lymphoma. Patients with SGF had excellent clinical outcomes with only one of seventeen patients experiencing relapse and relapse-related mortality. The incidence of PGF and SGF in patients receiving NMA conditioning and PTCy is low and is not impacted by HLA disparities between donors and recipients. PGF is more common in recipients with age ≥ 65, a diagnosis of MDS, MPN, or MDS/MPN-overlap, post-transplant HHV-6 viremia, and low CD34+ cell dose. Low total nucleated cell dose is also a risk factor for PGF in patients receiving a bone marrow graft source. Patients who experience PGF have poor outcomes due to high rates of nonrelapse mortality, whereas patients who experience SGF have excellent long-term outcomes.

Impact of CD34 positive cell dose in donor graft on the outcomes after haploidentical peripheral blood stem cell transplantation with post-transplant cyclophosphamide - A retrospective single-center study with a Japanese cohort

BACKGROUND

Haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) with post-transplant cyclophosphamide (PTCy) is an important therapeutic option for patients lacking an HLA-matched donor. However, the significance of CD34+ cell dose in grafts has not been fully elucidated.

OBJECTIVE

We aimed to explore the impact of CD34+ cell dose on outcomes after haplo-PBSCT with PTCy.

STUDY DESIGN

We retrospectively investigated 111 consecutive patients who underwent haplo-PBSCT with PTCy or HLA-matched PBSCT from related donors.

RESULTS

There were no statistically significant differences in 3-year overall survival (p = 0.559) or progression-free survival (p = 0.974) between haplo-PBSCT and matched PBSCT. Delayed neutrophil engraftment and a lower incidence of graft-versus-host disease were observed in haplo-PBSCT. The median dose of CD34+ cells was 4.9 × 106 /kg in 57 haplo-PBSCT and 4.5 × 106 /kg in 54 matched PBSCTs. Importantly, patients who underwent haplo-PBSCT with the administration of CD34+ cell at a dose of ≥4.0 × 106 /kg significantly had improved OS (p = 0.015) and decreased incidence of disease relapse (p = 0.001) without increasing incidence of GVHD.

CONCLUSION

Our data suggest that a higher dose of CD34+ cells in haplo-PBSCT with PTCy positively impacts the outcomes without an increase of GVHD.

Human Leukocyte Antigen-Haploidentical Haematopoietic Stem Cell Transplantation Using Post-Transplant Cyclophosphamide for Paediatric Haematological Malignancies

The use of human leukocyte antigen (HLA)-haploidentical haematopoietic stem cell transplantation (HSCT) with post-transplant cyclophosphamide (PTCY), which markedly reduces the risk of graft-versus-host disease, has rapidly increased worldwide, even in children. It was initially developed for post-transplant relapse or non-remission at transplant for patients with high-risk haematologic malignancies. However, this strategy is currently used more frequently for standard-risk, transplant-eligible paediatric haematological malignancies. It has recently been recognised in adults that the transplant outcomes after PTCY-based HLA-haploidentical HSCT are comparable with those achieved after HLA-matched HSCT. Therefore, even in children, parental donors who are HLA-haploidentical donors and cord blood are currently considered the next donor candidates when an HLA-matched related or unrelated donor is unavailable. This review addresses the current status of the use of haplo-HSCT with PTCY for paediatric haematologic malignancies and future directions for donor selection (sex, age, ABO blood type, and HLA disparity), donor source, the dose of infused CD34+ cells, optimal conditioning, the concomitant graft-versus-host disease prophylaxis other than PTCY, and the pharmacokinetic study of CY and CY metabolites. These aspects present key solutions for further improvements in the outcomes of haplo-HSCT with PTCY for paediatric haematological malignancies.

Stem Cells mobilization and collection in allogeneic related and unrelated donors: a single center experience with focus on plerixafor

INTRODUCTION

Poor CD34 + cells mobilization in allogeneic donors could affect transplant outcome. In a subgroup of patient mobilization with granulocyte colony-stimulating factor (G-CSF) alone is unsatisfactory, and Plerixafor could be used to enhance CD34 + cells release from bone marrow niche.

MATERIALS AND METHODS

We conducted a retrospective single-center, cohort study on healthy allogeneic donors both related and unrelated, treated by Udine Transfusion Center over the last 10 years (2012-2022). In the 195 allogeneic donors treated we analyzed age, sex, body weight, BMI, comorbidities, G-CSF dosage and even baseline white blood cell count as possible predictor of insufficient CD34 + cells mobilization on day 5. In the subgroup of related donors we evaluated even baseline CD34 + cells (measured before mobilization start). Processed donor blood volume, collection efficiency and apheresis product were examined. Additionally a comparative analysis was conducted between G-CSF alone treated donors and poor mobilizing ones, in which Plerixafor was administered at a dose of 0.24 mg/kg as a pre-emptive or rescue agent.

RESULTS

In 9 donors, due to poor mobilization (defined as CD34 + < 20/µL or estimated yield < 1 ×106 kg/recipient body weight), the use of plerixafor was necessary. PLX at a dose of 0.24 mg/kg was administered 5 h before collection, inducing an average increase of 5.1 (1.7-12.6) in CD34 + circulating cells. In this subgroup of patients, BMI and weight were significantly lower (p = 0.03). Interestingly, baseline CD34 + cells (measured before the onset of mobilization) also seems to predict poor mobilization (p = 0.003). In donors additionally treated with Plerixafor compared to those who received G-CSF alone, collection efficiency was higher (p = 0.02) and CD34 + cells collected were comparable (p = 0.2). Side effects related to the administration of plerixafor, if they occurred, were well tolerated.

CONCLUSIONS

Plerixafor is a safe and effective drug in the rescue and prevention of poor mobilization. New prospective studies on allogeneic donors should be performed to increase the treatable population to avoid inadequate collection and mobilization. New laboratory predictors such as baseline CD34 + cells should be investigated in larger cohorts and then used as early screening.