Unrelated cord blood compared with haploidentical grafts in patients with hematological malignancies

Unrelated cord blood transplantation vs. HLA-matched sibling transplantation for adults with B-cell acute lymphoblastic leukemia in complete remission: superior OS for patients with long-term survival

Background

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an important curative therapy for adult acute lymphoblastic leukemia (ALL). For patients who lack a human leukocyte antigen (HLA)-matched sibling donor, unrelated cord blood (UCB) is an alternative graft option. Previous studies have focused mainly on all T- and B-cell ALL (B-ALL) patients, while data related specifically to adult B-ALL patients after UCB transplantation (UCBT) are scarce.

Methods

We retrospectively compared the outcomes of UCBT and HLA-matched sibling transplantation (MST) in the treatment of adult B-ALL patients in complete remission (CR) at our center. From June 2006 to December 2020, 156 adult B-ALL patients who achieved CR before transplantation were enrolled. The main clinical outcomes of UCBT and MST were analyzed.

Results

Hematopoietic recovery was significantly faster in MST recipients than in UCBT recipients. Higher incidences of grades II-IV and III-IV acute graft-versus host disease (aGVHD) were found in UCBT recipients (P < 0.001 and = 0.03), while a lower incidence of extensive chronic GVHD (cGVHD) was found in UCBT recipients (P < 0.001). The cumulative incidences of 2-year non-relapse mortality (NRM), 2-year relapse, 5-year disease-free survival (DFS) and 5-year GVHD-free relapse-free survival (GRFS) were comparable between MST and UCBT recipients. The overall survival (OS) during the first 700 days was similar between the MST and UCBT groups, while the OS of patients with a survival time of more than 700 days in the UCBT group was better than that in the MST group according to multivariate analysis (P = 0.03).

Conclusions

Our study shows that when treating adult B-ALL patients in CR, UCBT can achieve comparable effects as MST, may provide superior OS for patients with long-term survival, and should be considered a good alternative.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03186-3.

Comparison of clinical outcomes between unrelated single umbilical cord blood and "ex-vivo" T-cell depleted haploidentical transplantation in children with hematological malignancies

BACKGROUND

Over the last two decades, umbilical cord blood (UCB) and haploidentical transplantation (HaploHSCT) have emerged as alternative sources of hematopoietic stem cell for allogeneic transplantation. There are few retrospective studies and no prospective studies comparing both types of alternative transplantation in pediatric patients.

RESULTS

We analyzed the data of 134 children with hematological malignancies who received a hematopoietic stem cell transplantation from a single umbilical cord blood (UCB) (n = 42) or an "ex-vivo" T-cell depleted transplant from a haploidentical-related donor (HaploHSCT) (n = 92) between 1996 and 2014. Hematological recovery was faster after HaploHSCT than the UCB transplant group (median times to neutrophil and platelet recovery: 13 vs. 16 days, 10 vs. 57 days, respectively) (P < 0.001). The HaploHSCT group had a significantly early immune reconstitution based on NK and CD8 + T cells compared with the UCB group. However, after the first year post-transplantation, HaploHSCT had a lower number of CD4 + T and B lymphocytes compared with the UCB transplant recipients. The cumulative incidence of TRM was 29±8% in the HaploHSCT group versus 40±5% in the UCB group. Relapse incidence was 21±7% in the HaploHSCT group and 19±8% in the UCB group. Probability of DFS was 58±8% in the HaploHSCT group versus 40±9% in the UCB group (P = 0.051).

CONCLUSIONS

TCD haploidentical transplant is associated with advantages in terms of engraftment and early immune reconstitution kinetics. TCD haploidentical transplant was associated with lower incidence of infectious and non-infectious complications, especially in the early phases of the transplant compared with UCB transplant recipients. However, there are no advantages in transplant outcomes compared with UCB transplant.

Clinical Outcomes of Unrelated Umbilical Cord Blood Graft vs. Haploidentical Donor Transplantation: Critical Issues for an Adequate Comparison

Unrelated umbilical cord blood (UCB) and haploidentical grafts have been used for allogeneic hematopoietic stem and progenitor cell (HSPC) transplantation in patients without a related or non-related human leukocyte antigen (HLA)-matched donor. The less stringent HLA-matching requirement in both sources raises an important possibility for patients in need of urgent transplantation to treat any hematological disease. Selection of the best alternative donor is a difficult task that will depend on donor criteria, center experience, patient disease conditions, and risk, among others. Most comparisons available in scientific publications between both graft sources are obtained from retrospective analysis in wide time windows and a heterogeneous number of patients, types of disease, disease stages, previous treatments, graft source, conditioning regimen, graft vs. host disease (GVHD) approach, and evaluable endpoints. There is also an evident impact of the economic traits since low-income countries must consider less expensive treatments to satisfy the needs of the patients in the most effective possible path. Therefore, haploidentical transplantation could be an appealing option, even though it has not been completely established if any chronic treatment derived from the procedure could become a higher cost. In Colombia, there is a huge experience in UCB transplantation especially in units of pediatric transplantation where benign indications are more common than in adults. Due to the availability of a public UCB bank and HLA high-resolution typing in Colombia, there is a wider inventory of cord blood donors. Unfortunately, we do not have an unrelated bone marrow donor registry, so UCB is an important source along with haploidentical transplantation to consider in decision-making. This minireview focuses on comparing the main issues associated with the use of both HSCP sources and provides tools for physicians who face the difficult decision between these alternative donor sources.

Cell and Gene Therapy for Anemia: Hematopoietic Stem Cells and Gene Editing

Hereditary anemia has various manifestations, such as sickle cell disease (SCD), Fanconi anemia, glucose-6-phosphate dehydrogenase deficiency (G6PDD), and thalassemia. The available management strategies for these disorders are still unsatisfactory and do not eliminate the main causes. As genetic aberrations are the main causes of all forms of hereditary anemia, the optimal approach involves repairing the defective gene, possibly through the transplantation of normal hematopoietic stem cells (HSCs) from a normal matching donor or through gene therapy approaches (either in vivo or ex vivo) to correct the patient’s HSCs. To clearly illustrate the importance of cell and gene therapy in hereditary anemia, this paper provides a review of the genetic aberration, epidemiology, clinical features, current management, and cell and gene therapy endeavors related to SCD, thalassemia, Fanconi anemia, and G6PDD. Moreover, we expound the future research direction of HSC derivation from induced pluripotent stem cells (iPSCs), strategies to edit HSCs, gene therapy risk mitigation, and their clinical perspectives. In conclusion, gene-corrected hematopoietic stem cell transplantation has promising outcomes for SCD, Fanconi anemia, and thalassemia, and it may overcome the limitation of the source of allogenic bone marrow transplantation.

Co-Transplantation of Haploidentical Stem Cells and a Dose of Unrelated Cord Blood in Pediatric Patients with Thalassemia Major

Allogeneic stem cell transplantation is a cure for patients suffering from thalassemia major (TM). Historically, patients were limited by the selection of donors, while the advancement of haploidentical stem cell transplantation (haplo-SCT) has greatly expanded the donor pool. However, the outcomes of haplo-SCT in TM recipients vary between different programs. In this study, we retrospectively studied 73 pediatric TM patients (median age, 7 years; range, 3 to 14 years) who underwent haplo-cord transplantation. Both the estimated overall survival and transfusion-free survival were 95.26% (CI 95.77% to 96.23%). Neither primary nor secondary graft failures were observed. The median follow-up period was 811 days (range, 370 to 1433 days). Median neutrophil and platelet engraftment times were 22 days (range, 8 to 48 days) and 20 days (range, 8 to 99 days), respectively. Acute graft-versus-host disease (aGVHD) was observed in 52% of patients and of these, 25% developed grade III to IV aGVHD. Cord blood engraftment was associated with delayed immune recovery and increased aGVHD severity. Viral DNAemia occurred in a relatively high proportion of patients but only 7% of patients developed CMV disease, while another 7% of patients had post-transplantation lymphoproliferative disorder. Long-term complication outcomes were good. Only one patient developed extensive chronic GVHD. No surviving patients were reliant on blood transfusion by the time this manuscript was submitted. This is one of the largest studies on the outcomes of pediatric TM patients who received stem cell transplantations from alternative donors. The haplo-cord program is safe and practical for TM patients that do not have matched donors.

Single Cord Blood Transplantation Versus Unmanipulated Haploidentical Transplantation for Adults with Acute Myeloid Leukemia in Complete Remission

Allogeneic hematopoietic cell transplantation (HCT) is a potentially curative post-remission therapy for adult patients with acute myeloid leukemia (AML) in complete remission (CR). The availability of alternative human leukocyte antigen (HLA)-mismatched donors, such as cord blood and haploidentical related donors, could allow patients to receive allogeneic HCT who are without an HLA-matched sibling or unrelated donor. The use of these alternative donors is preferable for patients with advanced disease due to the rapid availability. However, comparative data for cord blood transplantation (CBT) and haploidentical related donor transplantation (haplo-HCT) are limited for adult patients with AML in CR. We sought to compare overall survival (OS); leukemia-free survival (LFS); graft-versus-host disease (GVHD)-free, relapse-free survival (GRFS); and chronic GVHD-free, relapse-free survival (CRFS) between single-unit CBT (SCBT) and haplo-HCT recipients for adult patients with intermediate- or poor-risk AML in CR. We retrospectively analyzed and compared the results of allogeneic hematopoietic cell transplantation in 1313 adult patients with intermediate- or poor-risk AML in CR who received either SCBT (n = 1102) or unmanipulated haplo-HCT (n = 211) between 2007 and 2018 in Japan. Among the whole cohort, the cumulative incidences of neutrophil and platelet recovery were significantly lower in SCBT recipients compared with those in haplo-HCT recipients (P < .001 for neutrophil, P < .001 for platelet). SCBT was significantly associated with a higher incidence of grade II to IV acute GVHD and lower incidence of extensive chronic GVHD compared to haplo-HCT (P = .013 for grades II to IV acute GVHD; P = .006 for extensive chronic GVHD). Haplo-HCT recipients developed a higher incidence of cytomegalovirus (CMV) antigenemia compared to SCBT recipients (P = .004). In the multivariate analysis, there were no significant differences for grades III or IV acute GVHD (hazard ratio [HR], 1.17; 95% confidence interval [CI], .88 to 1.57; P = .26), relapse incidence (HR, 1.09; 95% CI, .76 to 1.58; P = .61), non-relapse mortality (HR, .83; 95% CI, .58 to 1.18; P = .32), OS (HR, .92; 95% CI, .70 to 1.20; P = .56), LFS (HR, .94; 95% CI, .73 to 1.21; P = .67), GRFS (HR, 1.12; 95% CI, .90 to 1.40; P = .27), or CRFS (HR, 1.15; 95% CI, .92 to 1.44; P = .19) between the two donor types. In the propensity score matching analysis, which identified 180 patients in each cohort, there were no significant differences in transplant outcomes between the two donor types, except for delayed neutrophil (P < .001) and platelet recovery (P < .001) and a higher incidence of grades II to IV acute GVHD (P = .052) in SCBT. SCBT and unmanipulated haplo-HCT had similar survival outcomes for adult patients with AML in CR despite the lower hematopoietic recovery and higher grade II to IV acute GVHD in SCBT recipients and the higher CMV antigenemia in haplo-HCT recipients.

Haploidentical Hematopoietic Stem Cell Transplantation Versus Umbilical Cord Blood Transplantation in Hematologic Malignancies: A Systematic Review and Meta-Analysis

Haploidentical hematopoietic stem cell transplantation (Haplo-SCT) and umbilical cord blood transplantation (UCBT) are two important alternatives when a matched sibling donor is unavailable. Several studies have reported inconsistent clinical outcomes comparing Haplo-SCT and UCBT. Therefore, it is necessary to synthesize the existing evidence regarding outcomes of stem cell transplantations comparing Haplo-SCT with UCBT. We searched article titles that compared transplantation with Haplo-SCT and UCBT in MEDLINE (PubMed), Cochrane library, and EMBASE database. To compare clinical outcomes between Haplo-SCT and UCBT, we performed a meta-analysis of 12 studies and reported the pooled odds ratios (ORs) of 6 end points including overall survival (OS), progression-free survival (PFS), nonrelapse mortality (NRM), relapse rate (RR), acute graft-versus-host disease (aGVHD), and chronic graft-versus-host disease (cGVHD). We found that Haplo-SCT was associated with a significantly superior OS (pooled OR of 0.74, 95% confidence interval [CI] 0.68 to 0.80) and PFS (0.77, 95% CI 0.72 to 0.83), as well as a lower NRM (0.72, 95% CI 0.64 to 0.80) and aGVHD (0.87, 95% CI 0.77 to 0.98) compared to the UCBT group. We also found a significantly increased risk of cGVHD in Haplo-SCT group (1.40, 95% CI 1.22 to 1.62). In terms of RR, Haplo-SCT was comparable to UCBT (0.91, 95% CI 0.79 to 1.05). Results of this meta-analysis demonstrate that Haplo-SCT results in better clinical outcomes compared to UCBT in terms of OS, PFS, TRM, and aGVHD, but is inferior to UCBT in terms of increased cGVHD risk. Further prospective comparisons between Haplo-SCT and UCBT are needed.

Outcomes of haploidentical vs matched sibling transplantation for acute myeloid leukemia in first complete remission

HLA-haploidentical hematopoietic cell transplantation (Haplo-HCT) using posttransplantation cyclophosphamide (PT-Cy) has improved donor availability. However, a matched sibling donor (MSD) is still considered the optimal donor. Using the Center for International Blood and Marrow Transplant Research database, we compared outcomes after Haplo-HCT vs MSD in patients with acute myeloid leukemia (AML) in first complete remission (CR1). Data from 1205 adult CR1 AML patients (2008-2015) were analyzed. A total of 336 patients underwent PT-Cy-based Haplo-HCT and 869 underwent MSD using calcineurin inhibitor-based graft-versus-host disease (GVHD) prophylaxis. The Haplo-HCT group included more reduced-intensity conditioning (65% vs 30%) and bone marrow grafts (62% vs 7%), consistent with current practice. In multivariable analysis, Haplo-HCT and MSD groups were not different with regard to overall survival (P = .15), leukemia-free survival (P = .50), nonrelapse mortality (P = .16), relapse (P = .90), or grade II-IV acute GVHD (P = .98). However, the Haplo-HCT group had a significantly lower rate of chronic GVHD (hazard ratio, 0.38; 95% confidence interval, 0.30-0.48; P < .001). Results of subgroup analyses by conditioning intensity and graft source suggested that the reduced incidence of chronic GVHD in Haplo-HCT is not limited to a specific graft source or conditioning intensity. Center effect and minimal residual disease-donor type interaction were not predictors of outcome. Our results indicate a lower rate of chronic GVHD after PT-Cy-based Haplo-HCT vs MSD using calcineurin inhibitor-based GVHD prophylaxis, but similar other outcomes, in patients with AML in CR1. Haplo-HCT is a viable alternative to MSD in these patients.

Haploidentical Hematopoietic Stem Cell Transplantation Followed by 'Post-Cyclophosphamide': The Future of Allogeneic Stem Cell Transplant

Allogeneic hematopoietic cell transplant (Allo-HCT) is a potentially curative therapy for many malignant and nonmalignant hematological diseases. However, a suitable human leukocyte antigens (HLAs)-matched donor may not be available when the patient is in urgent need of a stem cell transplant. This challenge has been ameliorated to a large extent by the introduction of haploidentical donors. This type of donor shares one HLA haplotype with the recipient. Therefore, a patient's full sibling has a 50% chance of being haploidentical and a patient's biologic parents and children will all be haploidentical, thus providing an immediately accessible, motivated donor for almost every recipient. Haploidentical transplants previously incurred prohibitively poor outcomes, preventing their widespread use. However, several recent advances have dramatically improved the results, making them a more viable donor source. In this review, we discuss different types of donors used for Allo-HCT with a particular focus on the use of haploidentical donors and their future potential.

Post transplant cyclophosphamide based haplo-identical transplant versus umbilical cord blood transplant; a meta-analysis

OBJECTIVES

Both haplo-identical transplant (haplo) and umbilical cord transplant (UC) are valuable graft options for patients without available matched relative. Previous studies showed inconsistent outcomes comparing Post transplant Cyclophosphamide based haplo (PTCy-haplo) and UC; therefore, we attempt to compare the studies by mean of meta-analysis.

METHODS

We searched for titles of articles in MEDLINE (PubMed), Cochrane library, EMBASE database and Google scholar that compared transplantation with PTCy-haplo versus UC. We conducted a random-effect meta-analysis of seven studies involving a total of 3434 participants and reported the pooled odd ratios (OR) of acute graft-versus-host disease (aGVHD), chronic graft-versus-host disease (cGVHD), relapse and overall survival (OS) between PTCy-haplo and UC groups.

RESULTS

We found a significantly decreased risk of aGVHD and relapse in the PTCy-haplo group compared to the UC group with a pooled OR of 0.78, 95% Confidence Interval (CI) 0.67-0.92, I2=0%, and 0.74, 95% CI 0.57-0.97, I2=23.9% respectively. We also found a significantly increased rate of cGVHD and OS with a pooled OR of 1.41, 95% CI 1.02-1.95, I2=56.8%, and 1.77, 95% CI 1.1-2.87, I2=82.5%, respectively.

CONCLUSION

Our meta-analysis of clinical trials demonstrated superior outcome from PTCy-haplo group compared to the UC group in terms of decreased rate of aGVHD and relapse as well as the increased rate of OS but inferior in terms of increased cGVHD risk compared to UC transplant.

[Haploidentical hematopoietic stem cell transplant: How to choose the best donor? Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

Haploidentical hematopoietic stem cell transplantation has been growing steadily since 2012. The SFGM-TC has twice published guidelines concerning T-cell repleted haploidentical grafts with high dose cyclophosphamide post-transplantation. The 2013 workshop recommended using the non-myeloablative Baltimore protocol with bone marrow and developed prospective protocols to evaluate these transplantations. The 2015 workshop reported improved results of reduced conditioning regimens in Hodgkin's lymphoma and intensive conditioning in myeloid hemopathies, and a similar outcome with 10/10 HLA matched donor with the same disease-risk score thus raising the question of the qualifier "alternative" for haploidentical transplants. The current work concerns the criteria for selecting the donor. The main criterion remains the absence of anti-HLA antibodies directed against the donor present in the recipient sera (DSA - Donor Specific Antibodies). In case of DSA and in the absence of an alternative donor, desensitization protocols exist. The other criteria are impossible to prioritize: age, sex, CMV, and blood type. The degree of relatedness and the number of HLA incompatibilities do not seem to be a criterion of choice. The 'ideal' donor would be a young man, CMV-matched, without major ABO incompatibility with a marrow transplant. There is insufficient data for the KIR-ligand and NIMA/NIPA mismatch. Peripheral stem cell grafts appear to yield more acute GVHD than bone marrow grafts after intensive conditioning, but with comparable survival rates. Based on the literature review, the comparison of haploidentical with unrelated donors encourages inclusion in existing national protocols randomizing these different donors.

Influence of Donor Type (Sibling versus Matched Unrelated Donor versus Haploidentical Donor) on Outcomes after Clofarabine-Based Reduced-Intensity Conditioning Allograft for Myeloid Malignancies

Clofarabine-based reduced-intensity conditioning (RIC) regimens are well-established schedules for allograft in patients with myeloid malignancies. A retrospective study was conducted including all adults allografted in our department with such a regimen and disease with the aim to assess whether or not the donor type (matched sibling [MSD], matched unrelated [MUD], or haploidentical [haplo]) impacted outcomes. Between October 2009 and February 2018, 118 patients met the inclusion criteria. Thirty-six, 55, and 27 patients received a graft from an MSD, MUD, or haplo donor, respectively. Peripheral blood stem cells (PBSCs) were the source of graft for all patients. The median age of the entire cohort was 62 years (range, 20 to 73), and the median follow-up was 31 months (range, 4.5 to 106). All patients engrafted except 1 haplo recipient. Neutrophils (>.5 × 10⁹/L) and platelets (50 × 10⁹/L) recoveries were significantly delayed in the haplo group (P = .0003 and P < .0001) compared with MSD and MUD. Acute grades II to IV or III to IV graft-versus-host disease (GVHD) incidences were similar between the 3 groups as well as the incidence of moderate or severe chronic GVHD. Also, similar 2-year overall survival (OS; 64.7% versus 73.9% versus 60.2%, P = .39), disease-free survival (DFS; 57.7% versus 70.9% versus and 53.6%, P = .1), and GVHD relapse-free survival (37.9% versus 54.3% versus 38.9%, P = .23) were observed between MSD versus MUD versus haplo groups. The same was true when considering only acute myeloid leukemia (AML) cases. In multivariate analysis the type of donor remained independent of outcomes in this series, whereas myelodysplastic syndrome (versus AML), high disease risk index, and older donor (≥50 years) were associated with lower OS and DFS. These data suggest that haplo donors are an acceptable alternative for patients receiving a clofarabine-based RIC PBSC allograft for myeloid malignancies who lack an MSD or a MUD.

Dynamical system modeling to simulate donor T cell response to whole exome sequencing-derived recipient peptides: Understanding randomness in alloreactivity incidence following stem cell transplantation

Quantitative relationship between the magnitude of variation in minor histocompatibility antigens (mHA) and graft versus host disease (GVHD) pathophysiology in stem cell transplant (SCT) donor-recipient pairs (DRP) is not established. In order to elucidate this relationship, whole exome sequencing (WES) was performed on 27 HLA matched related (MRD), & 50 unrelated donors (URD), to identify nonsynonymous single nucleotide polymorphisms (SNPs). An average 2,463 SNPs were identified in MRD, and 4,287 in URD DRP (p<0.01); resulting peptide antigens that may be presented on HLA class I molecules in each DRP were derived in silico (NetMHCpan ver2.0) and the tissue expression of proteins these were derived from determined (GTex). MRD DRP had an average 3,670 HLA-binding-alloreactive peptides, putative mHA (pmHA) with an IC50 of <500 nM, and URD, had 5,386 (p<0.01). To simulate an alloreactive donor cytotoxic T cell response, the array of pmHA in each patient was considered as an operator matrix modifying a hypothetical cytotoxic T cell clonal vector matrix; each responding T cell clone’s proliferation was determined by the logistic equation of growth, accounting for HLA binding affinity and tissue expression of each alloreactive peptide. The resulting simulated organ-specific alloreactive T cell clonal growth revealed marked variability, with the T cell count differences spanning orders of magnitude between different DRP. Despite an estimated, uniform set of constants used in the model for all DRP, and a heterogeneously treated group of patients, higher total and organ-specific T cell counts were associated with cumulative incidence of moderate to severe GVHD in recipients. In conclusion, exome wide sequence differences and the variable alloreactive peptide binding to HLA in each DRP yields a large range of possible alloreactive donor T cell responses. Our findings also help understand the apparent randomness observed in the development of alloimmune responses.

Haploidentical hematopoietic cell transplantation for adult acute myeloid leukemia: a position statement from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Allogeneic blood or marrow hematopoietic cell transplantation continues to be the most potent anti-leukemic treatment for adult patients with standard, high-risk, or chemo-refractory acute myeloid leukemia. Until recently, this procedure was generally limited to those recipients who had an available matched-sibling donor or matched-unrelated donor. Technical advances in graft cell processing and manipulation, control of bidirectional T cell alloreactivity, graft-versus-host disease prophylaxis, and other supportive measures in haploidentical transplantation now enable nearly all patients with acute myeloid leukemia to benefit from the graft-versus-leukemia effect with substantial reduction in procedure-related mortality. Over recent years, haploidentical donors have been increasingly adopted as a valid donor source in allogeneic hematopoietic cell transplantation for acute myeloid leukemia in the absence of an HLA-matched donor. Among centers of the European Society for Blood and Marrow Transplantation, the use of haploidentical related donor transplantation has increased by 250% since 2010, and 291% since 2005. On behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, we summarize recent utilization trends in haploidentical transplantation for acute myeloid leukemia and describe the transformative changes in haploidentical hematopoietic cell transplantation techniques over the past decade, which have led to the current widespread use of this procedure. Furthermore, we review the efficacy of haploidentical hematopoietic cell transplantation for acute myeloid leukemia from available studies, including preliminary comparative studies, and bring attention to remaining unanswered questions and directions for future research. We conclude this report with our recommendations for the role of haploidentical hematopoietic cell transplantation in acute myeloid leukemia.

Advances in haploidentical stem cell transplantation for hematologic malignancies

One of the most important advances in allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the use of alternative donors and cell sources, such as haploidentical transplants (haplo-HSCT) from family donors. Several approaches have been developed to overcome the challenging bidirectional alloreactivity. We discuss these approaches, including ex vivo T-cell-depleted grafts with megadose of CD34(+) cells, not requiring immunosuppression after allogeneic transplantation for graft-versus-host disease (GVHD) prophylaxis, and other strategies using unmanipulated T-cell-replete grafts with intensive immunosuppression or post-transplantation cyclophosphamide to minimize the GVHD. We also address the role of other strategies developed in the context of the haplo-HSCT platforms, such as ex vivo selective depletion of alloreactive donor T-cell subpopulations, infusion of antigen-specific T-cells against several pathogens, and infusion of regulatory T-cells, among other experimental approaches. Finally, some considerations about the selection of the most suitable donor, when more than one family member is available, are also addressed.

How do we choose the best donor for T-cell-replete, HLA-haploidentical transplantation?

In haploidentical stem cell transplantations (haplo-SCT), nearly all patients have more than one donor. A key issue in the haplo-SCT setting is the search for the best donor, because donor selection can significantly impact the incidences of acute and chronic graft-versus-host disease, transplant-related mortality, and relapse, in addition to overall survival. In this review, we focused on factors associated with transplant outcomes following unmanipulated haplo-SCT with anti-thymocyte globulin (ATG) or after T-cell-replete haplo-SCT with post-transplantation cyclophosphamide (PT/Cy). We summarized the effects of the primary factors, including donor-specific antibodies against human leukocyte antigens (HLA); donor age and gender; killer immunoglobulin-like receptor-ligand mismatches; and non-inherited maternal antigen mismatches. We also offered some expert recommendations and proposed an algorithm for selecting donors for unmanipulated haplo-SCT with ATG and for T-cell-replete haplo-SCT with PT/Cy.

Autologous stem cell transplantation versus alternative allogeneic donor transplants in adult acute leukemias

The availability of alternative sources of stem cells including most recently T-replete haploidentical marrow or peripheral blood, and the increasing use of reduced-intensity conditioning (RIC), renders feasible an allogeneic transplant to almost all patients with acute leukemia up to 70 years of age. Autologous stem cell transplantation (ASCT) for consolidation of complete remission (CR), however, offers in some circumstances an alternative option. Although associated with a higher relapse rate, autologous transplant benefits from a lower non-relapse mortality, the absence of graft-versus-host disease (GVHD), and a better quality of life for long-term survivors. The recent use of intravenous busulfan (IVBU) with high-dose melphalan, better monitoring of minimal residual disease (MRD), and maintenance therapy post autografting bring new interest. Few retrospective studies compared the outcome following alternative donor versus autologous transplants for remission consolidation. Genoidentical and phenoidentical allogeneic stem cell transplantations are undisputed gold standards, but there are no data showing the superiority of alternative allogeneic donor over autologous transplantation, at the time of undetectable MRD, in patients with good- and intermediate-1 risk acute myelocytic leukemia (AML) in first complete remission (CR1), acute promyelocytic leukemia in second complete remission (CR2), and Philadelphia chromosome-positive (Ph(+)) acute lymphocytic leukemia (ALL).

Haploidentical bone marrow and stem cell transplantation: experience with post-transplantation cyclophosphamide

Allogeneic blood or bone marrow transplantation (BMT) is a potentially curative therapy for high-risk hematologic malignancies not curable by standard chemotherapy, but the procedure is limited by the availability of human leukocyte antigen-matched donors for many patients, as well as toxicities including graft-versus-host disease (GVHD). Our group has developed the use of high-dose post-transplantation cyclophosphamide (PTCy) to selectively remove alloreactive T cells without compromising engraftment. This protocol has allowed for successful transplantation of human leukocyte antigen (HLA)-haploidentical (haplo) grafts, thus expanding the donor pool for the many patients who would not otherwise be a candidate for this life-saving procedure. In this review we will summarize the data that led to the development of PTCy, then focus on the outcomes of haploBMT trials with PTCy across different transplant platforms for patients with malignant hematologic diseases, and finally we will discuss emerging evidence that suggests equivalency of haploBMT with PTCy compared with more traditional transplants.

Hematopoietic stem cell transplantation for patients with AML in first complete remission

Postremission therapy in patients with acute myeloid leukemia (AML) may consist of continuing chemotherapy or transplantation using either autologous or allogeneic stem cells. Patients with favorable subtypes of AML generally receive chemotherapeutic consolidation, although recent studies have also suggested favorable outcome after hematopoietic stem cell transplantation (HSCT). Although allogeneic HSCT (alloHSCT) is considered the preferred type of postremission therapy in poor- and very-poor-risk AML, the place of alloHSCT in intermediate-risk AML is being debated, and autologous HSCT is considered a valuable alternative that may be preferred in patients without minimal residual disease after induction chemotherapy. Here, we review postremission transplantation strategies using either autologous or allogeneic stem cells. Recent developments in the field of alternative donors, including cord blood and haploidentical donors, are highlighted, and we discuss reduced-intensity alloHSCT in older AML recipients who represent the predominant category of patients with AML who have a high risk of relapse in first remission.

Banking or Bankrupting: Strategies for Sustaining the Economic Future of Public Cord Blood Banks

Background

Cord blood is an important source of stem cells. However, nearly 90% of public cord blood banks have declared that they are struggling to maintain their financial sustainability and avoid bankruptcy. The objective of this study is to evaluate how characteristics of cord blood units influence their utilization, then use this information to model the economic viability and therapeutic value of different banking strategies.

Methods

Retrospective analysis of cord blood data registered between January 1st, 2009 and December 31st, 2011 in Bone Marrow Donor Worldwide. Data were collected from four public banks in France, Germany and the USA. Samples were eligible for inclusion in the analysis if data on cord blood and maternal HLA typing and biological characteristics after processing were available (total nucleated and CD34+ cell counts). 9,396 banked cord blood units were analyzed, of which 5,815 were Caucasian in origin. A multivariate logistic regression model assessed the influence of three parameters on the CBU utilization rate: ethnic background, total nucleated and CD34+ cell counts. From this model, we elaborated a Utilization Score reflecting the probability of transplantation for each cord blood unit. We stratified three Utilization Score thresholds representing four different banking strategies, from the least selective (scenario A) to the most selective (scenario D). We measured the cost-effectiveness ratio for each strategy by comparing performance in terms of number of transplanted cord blood units and level of financial deficit.

Results

When comparing inputs and outputs over three years, Scenario A represented the most extreme case as it delivered the highest therapeutic value for patients (284 CBUs transplanted) along with the highest financial deficit (USD 5.89 million). We found that scenario C resulted in 219 CBUs transplanted with a limited deficit (USD 0.98 million) that charities and public health could realistically finance over the long term. We also found that using a pre-freezing level of 18 x 10⁸ TNC would be the most cost-effective strategy for a public bank.

Conclusion

Our study shows that a swift transition from strategy A to C can play a vital role in preventing public cord blood banks worldwide from collapsing.

Modern approaches to HLA-haploidentical blood or marrow transplantation

Allogeneic blood or bone-marrow transplantation (alloBMT) is a potentially curative treatment for a variety of haematological malignancies and nonmalignant diseases. Historically, human leukocyte antigen (HLA)-matched siblings have been the preferred source of donor cells owing to superior outcomes compared with alloBMT using other donors. Although only approximately one-third of patients have an HLA-matched sibling, nearly all patients have HLA-haploidentical related donors. Early studies using HLA-haploidentical alloBMT resulted in unacceptably high rates of graft rejection and graft-versus-host disease (GVHD), leading to high nonrelapse mortality and consequently poor survival. Several novel approaches to HLA-haploidentical alloBMT have yielded encouraging results with high rates of successful engraftment, effective GVHD control and favourable outcomes. In fact, outcomes of several retrospective comparative studies seem similar to those seen using other allograft sources, including those of HLA-matched-sibling alloBMT. In this Review, we provide an overview of the three most-developed approaches to HLA-haploidentical alloBMT: T-cell depletion with 'megadose' CD34(+) cells; granulocyte colony-stimulating factor-primed allografts combined with intensive pharmacological immunosuppression, including antithymocyte globulin; and high-dose, post-transplantation cyclophosphamide. We review the preclinical and biological data supporting each approach, results from major clinical studies, and completed or ongoing clinical studies comparing these approaches with other alloBMT platforms.

Alternative Donor Transplantation for Acute Myeloid Leukemia

Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative therapy for adult patients with acute myeloid leukemia (AML), but its use for consolidation therapy after first remission with induction chemotherapy used to be limited to younger patients and those with suitable donors. The median age of AML diagnosis is in the late 60s. With the introduction of reduced-intensity conditioning (RIC), many older adults are now eligible to receive allo-HCT, including those who are medically less fit to receive myeloablative conditioning. Furthermore, AML patients commonly have no human leukocyte antigen (HLA)-identical or medically suitable sibling donor available to proceed with allo-HCT. Technical advances in donor matching, suppression of alloreactivity, and supportive care have made it possible to use alternative donors, such as unrelated umbilical cord blood (UCB) and partially HLA-matched related (haploidentical) donors. Outcomes after alternative donor allo-HCT are now approaching the outcomes observed for conventional allo-HCT with matched related and unrelated donors. Thus, with both UCB and haploidentical donors available, lack of donor should rarely be a limiting factor in offering an allo-HCT to adults with AML.