Reduced late mortality risk contributes to similar survival after double-unit cord blood transplantation compared with related and unrelated donor hematopoietic stem cell transplantation

The impacts of total body irradiation on umbilical cord blood hematopoietic stem cell transplantation

Background

Umbilical cord blood hematopoietic stem cells are commonly used for hematopoietic system reconstitution in recipients after umbilical cord blood transplantation (UCBT). However, the optimal conditioning regimen for UCBT remains a topic of debate. The exact impact of total body irradiation (TBI) as a part of conditioning regimens remains unknown.

Objectives

The aim of this study was to evaluate the impacts of TBI on UCBT outcomes.

Design

This was a multi-institution retrospective study.

Methods

A retrospective analysis was conducted on the outcomes of 136 patients receiving UCBT. Sixty-nine patients received myeloablative conditioning (MAC), in which 33 underwent TBI and 36 did not, and 67 patients received reduced-intensity conditioning (RIC), in which 43 underwent TBI and 24 did not. Univariate and multivariate analyses were conducted to compare the outcomes and the post-transplant complications between patients who did and did not undergo TBI in the MAC subgroup and RIC subgroup, respectively.

Results

In the RIC subgroup, patients who underwent TBI had superior overall survival (adjusted hazard ratio [aHR] = 0.25, 95% confidence interval [CI]: 0.09-0.66, p = 0.005) and progression-free survival (aHR = 0.26, 95% CI: 0.10-0.66, p = 0.005). However, in the MAC subgroup, there were no statistically significant differences between those receiving and not receiving TBI.

Conclusion

In the setting of RIC in UCBT, TBI utilization can improve overall survival and progression-free survival. However, TBI does not show superiority in the MAC setting.

Unrelated Donor Cord Blood Transplantation in Children: Lessons Learned Over 3 Decades

Four decades ago, Broxmeyer et al. demonstrated that umbilical cord blood (CB) contained hematopoietic stem cells (HSC) and hypothesized that CB could be used as a source of donor HSC for rescue of myeloablated bone marrow. In 1988, Gluckman et al. reported the first successful matched sibling cord blood transplant (CBT) in a child with Fanconi Anemia. In 1991, Rubinstein et al. established an unrelated donor CB bank, and in 1993, the first unrelated CBT used a unit from this bank. Since that time, >40 000 CBTs have been performed worldwide. Early outcomes of CBT were mixed and demonstrated the importance of cell dose from the CB donor. We hypothesized that improvements in CB banking and transplantation favorably impacted outcomes of CBT today and performed a retrospective study combining data from Eurocord and Duke University in 4834 children transplanted with a single unrelated CB unit (CBU) from 1993 to 2019. Changes in standard transplant outcomes (overall survival [OS], disease free survival [DFS], acute and chronic graft-versus-host disease [GvHD], treatment related mortality [TRM], and relapse) over 3 time periods (1: <2005; 2: 2005 to <2010; and 3: >2010 to 2019) were studied. Increased cell dose and degree of HLA matching were observed over time. OS, times to engraftment, and DFS improved over time. The incidence of TRM and GvHD decreased while the incidence of relapse remained unchanged. Relative contributions of cell dose and HLA matching to transplant outcomes were also assessed and showed that HLA matching was more important than cell dose in this pediatric cohort.

Lymphoid and myeloid immune cell reconstitution after nicotinamide-expanded cord blood transplantation

Omidubicel (nicotinamide-expanded cord blood) is a potential alternative source for allogeneic hematopoietic cell transplantation (HCT) when an HLA-identical donor is lacking. A phase I/II trial with standalone omidubicel HCT showed rapid and robust neutrophil and platelet engraftment. In this study, we evaluated the immune reconstitution (IR) of patients receiving omidubicel grafts during the first 6 months post-transplant, as IR is critical for favorable outcomes of the procedure. Data was collected from the omidubicel phase I-II international, multicenter trial. The primary endpoint was the probability of achieving adequate CD4+ T-cell IR (CD4IR: > 50 × 106/L within 100 days). Secondary endpoints were the recovery of T-cells, natural killer (NK)-cells, B-cells, dendritic cells (DC), and monocytes as determined with multicolor flow cytometry. LOESS-regression curves and cumulative incidence plots were used for data description. Thirty-six omidubicel recipients (median 44; 13-63 years) were included, and IR data was available from 28 recipients. Of these patients, 90% achieved adequate CD4IR. Overall, IR was complete and consisted of T-cell, monocyte, DC, and notably fast NK- and B-cell reconstitution, compared to conventional grafts. Our data show that transplantation of adolescent and adult patients with omidubicel results in full and broad IR, which is comparable with IR after HCT with conventional graft sources.

Guidelines for the Prevention and Management of Graft-versus-Host Disease after Cord Blood Transplantation

The incidence of graft-versus-host disease (GVHD) after cord blood (CB) transplantation (CBT) is lower than expected given the marked degree of human leukocyte antigen (HLA)-mismatch of CB grafts. While the exact mechanism that underlies this biology remains unclear, it is hypothesized to be due to the low number of mostly immature T-cells infused as part of the graft1,2, and increased tolerance of CB-derived lymphocytes induced by the state of pregnancy. Nevertheless, acute GVHD (aGVHD) is a significant complication of CBT. In contrast, the incidence of chronic GVHD (cGVHD) following CBT is lower than what is observed following matched related or unrelated donor HSC transplantation (HSCT)3-6. This review outlines the guidelines for the prevention and management of acute and chronic GVHD following CBT.

Adult cord blood transplant results in comparable overall survival and improved GRFS vs matched related transplant

We compared outcomes among adult matched related donor (MRD) patients undergoing peripheral blood stem cell transplantation and adult patients undergoing double unit cord blood transplantation (CBT) at our center between 2010 and 2017. A total of 190 CBT patients were compared with 123 MRD patients. Median follow-up was 896 days (range, 169-3350) among surviving CBT patients and 1262 days (range, 249-3327) among surviving MRD patients. Comparing all CBT with all MRD patients, overall survival (OS) was comparable (P = .61) and graft-versus-host disease (GVHD) relapse-free survival (GRFS) was significantly improved among CBT patients (P = .0056), primarily because of decreased moderate to severe chronic GVHD following CBT (P < .0001; hazard ratio [HR], 3.99; 95% confidence interval [CI], 2.26-7.04). Among patients undergoing our most commonly used MRD and umbilical cord blood (CB) myeloablative regimens, OS was comparable (P = .136) and GRFS was significantly improved among CBT patients (P = .006). Cumulative incidence of relapse trended toward decreased in the CBT group (P = .075; HR, 1.85; CI 0.94-3.67), whereas transplant-related mortality (TRM) was comparable (P = .55; HR, 0.75; CI, 0.29-1.95). Among patients undergoing our most commonly used nonmyeloablative regimens, OS and GRFS were comparable (P = .158 and P = .697). Cumulative incidence of both relapse and TRM were comparable (P = .32; HR, 1.35; CI, 0.75-2.5 for relapse and P = .14; HR, 0.482; CI, 0.18-1.23 for TRM). Our outcomes support the efficacy of CBT and suggest that among patients able to tolerate more intensive conditioning regimens at high risk for relapse, CB may be the preferred donor source.

The wider perspective: cord blood banks and their future prospects

Over the past three decades, cord blood transplantation (CBT) has established its role as an alternative allograft stem cell source. But the future of stored CB units should be to extend their use in updated transplant approaches and develop new CB applications. Thus, CBT will require a coordinated, multicentric, review of transplantation methods and an upgrade and realignment of banking resources and operations. Significant improvements have already been proposed to support the clinical perspective including definition of the cellular threshold for engraftment, development of transplantation methods for adult patients, engraftment acceleration with single cell expansion and homing technologies, personalised protocols to improve efficacy, use of adoptive cell therapy to mitigate delayed immune reconstitution, and further enhancement of the graft-versus-leukaemia effect using advanced therapies. The role of CB banks in improving transplantation results are also critical by optimizing the collection, processing, storage and characterization of CB units, and improving reproducibility, efficiency and cost of banking. But future developments beyond transplantation are needed. This implies the extension from transplantation banks to banks that support cell therapy, regenerative medicine and specialized transfusion medicine. This new "CB banking 2.0" concept will require promotion of international scientific and technical collaborations between bank specialists, clinical investigators and transplant physicians.

Rapid Donor Identification Improves Survival in High-Risk First-Remission Patients With Acute Myeloid Leukemia

PURPOSE

Patients with acute myeloid leukemia with high-risk cytogenetics in first complete remission (CR1) achieve better outcomes if they undergo allogeneic hematopoietic cell transplantation (HCT) compared with consolidation chemotherapy alone. However, only approximately 40% of such patients typically proceed to HCT.

METHODS

We used a prospective organized approach to rapidly identify donors to improve the allogeneic HCT rate in adults with high-risk acute myeloid leukemia in CR1. Newly diagnosed patients had cytogenetics obtained at enrollment, and those with high-risk cytogenetics underwent expedited HLA typing and were encouraged to be referred for consultation with a transplantation team with the goal of conducting an allogeneic HCT in CR1.

RESULTS

Of 738 eligible patients (median age, 49 years; range, 18-60 years of age), 159 (22%) had high-risk cytogenetics and 107 of these patients (67%) achieved CR1. Seventy (65%) of the high-risk patients underwent transplantation in CR1 (P < .001 compared with the historical rate of 40%). Median time to HCT from CR1 was 77 days (range, 20-356 days). In landmark analysis, overall survival (OS) among patients who underwent transplantation was significantly better compared with that of patients who did not undergo transplantation (2-year OS, 48% v 35%, respectively [P = .031]). Median relapse-free survival after transplantation in the high-risk cohort who underwent transplantation in CR1 (n = 70) was 11.5 months (range, 4-47 months), and median OS after transplantation was 14 months (range, 4-44 months).

CONCLUSION

Early cytogenetic testing with an organized effort to identify a suitable allogeneic HCT donor led to a CR1 transplantation rate of 65% in the high-risk group, which, in turn, led to an improvement in OS when compared with the OS of patients who did not undergo transplantation.

Application of high-throughput next-generation sequencing for HLA typing of DNA extracted from postprocessing cord blood units

Cord blood has become an acceptable source of hematopoietic stem cells for transplantation. HLA plays a major role in hematopoietic stem cell transplantation (HSCT). Typing of cord blood samples for HLA alleles has been performed based on the serological and molecular methods. However, with the advent of next-generation sequencing technology, HLA typing becomes more accurate and unambiguous (upto intron level). Contamination of cord blood cells with erythropoietic cells poses a challenge in DNA extraction and downstream application. In the present study, DNA extracted from buffy coat of cord blood samples was typed for HLA-A, -B, -C, DRB1, and DQB1 alleles by Illumina miniseq and the sequences were aligned, phased, and mapped by MIA FORA software algorithms. Most frequent alleles found were HLA A*01:01:01 (17%), A*24:02:01 (15.1%), A*11:01:01 (13.6%), B*40:06:01 (10.7%), C*06:02:01 (17.7%), C*04:01:01 (14.2%), C*15:02:01 (11.4%), C*07:02:01 (10.7%), DRB1*07:01:01 (15.9%), DRB1*10:01:01 (10.2%), DQB1*06:01:01 (17.4%), DQB1*05:01:01 (12.4%), and DQB1*05:03:01 (10.4%). One null allele (A*24:11N), two novel alleles in B loci and three rare alleles (B*40:06:04, B*51:01:05, and C*01:44) were also identified in the present study. This study shows that high-throughput, unambiguous (third-field resolution) HLA typing can be performed on cord blood samples. In order to preserve the precious sample for future use, minimal amount of cord blood samples (postprocessing) could be used for HLA typing purpose.

Impacts and Challenges of Advanced Diagnostic Assays for Transplant Infectious Diseases

The advanced technologies described in this chapter should allow for full inventories to be made of bacterial genes, their time- and place-dependent expression, and the resulting proteins as well as their outcome metabolites. The evolution of these molecular technologies will continue, not only in the microbial pathogens but also in the context of host-pathogen interactions targeting human genomics and transcriptomics. Their performance characteristics and limitations must be clearly understood by both laboratory personnel and clinicians to ensure proper utilization and interpretation.

Ex Vivo Mesenchymal Precursor Cell-Expanded Cord Blood Transplantation after Reduced-Intensity Conditioning Regimens Improves Time to Neutrophil Recovery

We previously showed the safety of using cord blood (CB) expanded ex vivo in cocultures with allogeneic mesenchymal precursor cells (MPC) after myeloablative conditioning with faster recovery of neutrophils and platelets compared with historical controls. Herein, we report the transplantation outcomes of 27 patients with hematologic cancers who received 1 CB unit expanded ex vivo with MPCs in addition to an unmanipulated CB (MPC group) after reduced-intensity conditioning (RIC). The results in this group were compared with 51 historical controls who received 2 unmanipulated CB units (control group). The analyses were stratified for 2 RIC treatment groups: (1) total body irradiation 200 cGy + cyclophosphamide + fludarabine) (TCF), and (2) fludarabine + melphalan  (FM). Coculture of CB with MPCs led to an expansion of total nucleated cells by a median factor of 12 and of CD34⁺ cells by a median factor of 49. In patients in whom engraftment occurred, the median time to neutrophil engraftment was 12 days in the MPC group, as compared with 16 days in controls (P = .02). The faster neutrophil engraftment was observed in both RIC groups. The cumulative incidence of neutrophil engraftment on day 26 was 75% with expansion versus 50% without expansion in patients who received FM as the RIC regimen (P = .03). Incidence of neutrophil engraftment was comparable in MPC and control groups if treated with TCF (82% versus 79%, P = .40). Transplantation of CB units expanded with MPCs is safe and effective with faster neutrophil engraftment even after RIC regimens.

Alternative donors for allogeneic hematopoietic stem cell transplantation in poor-risk AML in CR1

Allogeneic hematopoietic stem cell transplantation (alloHSCT) remains the treatment of choice to consolidate remission in patients with poor-risk acute myeloid leukemia (AML). With increasing alternative donors available, the preferred donor or stem cell source is debated. We set out to study outcome in recipients of alloHSCT with poor-risk AML in first complete remission (CR1) by donor type. A total of 6545 adult patients with poor-risk AML in CR1 receiving an alloHSCT using matched related donor (MRD, n = 3511) or alternative donors, including 10/10 (n = 1959) or 9/10 matched unrelated donors (MUDs, n = 549), umbilical cord blood (UCB) grafts (n = 333), or haplo-identical (haplo) donors (n = 193) were compared. Overall survival (OS) at 2 years following MRD alloHSCT was an estimated 59 ± 1%, which did not differ from 10/10 MUD (57 ± 1%) and haplo alloHSCT (57 ± 4%). OS, however, was significantly lower for 9/10 MUD alloHSCT (49 ± 2%) and UCB grafts (44 ± 3%), respectively (P < .001). Nonrelapse mortality (NRM) depended on donor type and was estimated at 26 ± 3% and 29 ± 3% after haplo alloHSCT and UCB grafts at 2 years vs 15 ± 1% following MRD alloHSCT. Multivariable analysis confirmed the impact of donor type with OS following MRD, 10/10 MUD, and haplo alloHSCT not being statistically significantly different. NRM was significantly higher for alternative donors as compared with MRD alloHSCT. Collectively, these results suggest that alloHSCT with MRDs and 10/10 MUDs may still be preferred in patients with poor-risk AML in CR1. If an MRD or 10/10 MUD is not available, then the repertoire of alternative donors includes 9/10 MUD, UCB grafts, and haplo-identical donors. The latter type of donor is increasingly applied and now approximates results with matched donors.

The effect of inter-unit HLA matching in double umbilical cord blood transplantation for acute leukemia

The effects of inter-unit HLA-match on early outcomes with regards to double cord blood transplantation have not been established. Therefore, we studied the effect of inter-unit HLA-mismatching on the outcomes of 449 patients with acute leukemia after double cord blood transplantation. Patients were divided into two groups: one group that included transplantations with inter-unit mismatch at 2 or less HLA-loci (n=381) and the other group with inter-unit mismatch at 3 or 4 HLA-loci (n=68). HLA-match considered low resolution matching at HLA-A and -B loci and allele-level at HLA-DRB1, the accepted standard for selecting units for double cord blood transplants. Patients', disease, and transplant characteristics were similar in the two groups. We observed no effect of the degree of inter-unit HLA-mismatch on neutrophil (Hazard Ratio 1.27, P=0.11) or platelet (Hazard Ratio 0.1.13, P=0.42) recovery, acute graft-versus-host disease (Hazard Ratio 1.17, P=0.36), treatment-related mortality (Hazard Ratio 0.92, P=0.75), relapse (Hazard Ratio 1.18, P=0.49), treatment failure (Hazard Ratio 0.99, P=0.98), or overall survival (Hazard Ratio 0.98, P=0.91). There were no differences in the proportion of transplants with engraftment of both units by three months (5% after transplantation of units with inter-unit mismatch at ≤2 HLA-loci and 4% after transplantation of units with inter-unit mismatch at 3 or 4 HLA-loci). Our observations support the elimination of inter-unit HLA-mismatch criterion when selecting cord blood units in favor of optimizing selection based on individual unit characteristics.

Excellent T-cell reconstitution and survival depend on low ATG exposure after pediatric cord blood transplantation

Successful immune reconstitution (IR) is associated with improved outcomes following pediatric cord blood transplantation (CBT). Usage and timing of anti-thymocyte globulin (ATG), introduced to the conditioning to prevent graft-versus-host disease and graft failure, negatively influences T-cell IR. We studied the relationships among ATG exposure, IR, and clinical outcomes. All pediatric patients receiving a first CBT between 2004 and 2015 at the University Medical Center Utrecht were included. ATG-exposure measures were determined with a validated pharmacokinetics model. Main outcome of interest was early CD4⁺ IR, defined as CD4⁺ T-cell counts >50 × 10⁶/L twice within 100 days after CBT. Other outcomes of interest included event-free survival (EFS). Cox proportional-hazard and Fine-Gray competing-risk models were used. A total of 137 patients, with a median age of 7.4 years (range, 0.2-22.7), were included, of whom 82% received ATG. Area under the curve (AUC) of ATG after infusion of the cord blood transplant predicted successful CD4⁺ IR. Adjusted probability on CD4⁺ IR was reduced by 26% for every 10-point increase in AUC after CBT (hazard ratio [HR], 0.974; P < .0001). The chance of EFS was higher in patients with successful CD4⁺ IR (HR, 0.26; P < .0001) and lower ATG exposure after CBT (HR, 1.005; P = .0071). This study stresses the importance of early CD4⁺ IR after CBT, which can be achieved by reducing the exposure to ATG after CBT. Individualized dosing of ATG to reach optimal exposure or, in selected patients, omission of ATG may contribute to improved outcomes in pediatric CBT.

Autoimmune hemolysis and immune thrombocytopenic purpura after cord blood transplantation may be life-threatening and warrants early therapy with rituximab

Autoimmune hemolysis (AH) and immune thrombocytopenic purpura (ITP) are recognized complications after cord blood transplantation (CBT). We evaluated the incidence and characteristics of AH/ITP after double-unit CBT in a day 100 landmark analysis of 152 patients (median age 36 years, range 0.9-70 years) transplanted for hematologic malignancies with myeloablative or nonmyeloablative conditioning and calcineurin inhibitor (CNI)/mycophenolate mofetil. With a median 5.2-year (range 1.6-9.7 years) survivor follow-up, 10 patients developed autoimmune cytopenias (8 AH, 1 ITP, 1 both) at a median of 10.4 months (range 5.8-24.5) post CBT for a 7% cumulative incidence 3 years after the day 100 landmark. Six patients presented with severe disease (hemoglobin ⩽6 g/dL and/or platelets <20 × 10⁹/L). All AH patients were direct antiglobulin test positive. All 10 cases developed during immunosuppression taper with 8 having prior acute GVHD. All 10 patients received rituximab 2-18 days after diagnosis, and corticosteroids combined with rituximab within <7 days was the most effective. No patient died of AH/ITP. AH/ITP occurs infrequently after CBT but may be life-threatening requiring emergency therapy. Rituximab combined with corticosteroids at diagnosis is warranted in patients with severe disease.

Chronic graft versus host disease burden and late transplant complications are lower following adult double cord blood versus matched unrelated donor peripheral blood transplantation

Adult umbilical cord blood transplantation (CBT) has emerged as an important option for patients lacking matched related (MRD) and matched unrelated donors (MUD). We compared chronic GVHD (cGVHD) incidence, immunosuppression burden and late infections and hospitalizations in consecutive patients undergoing CBT (n=51) versus peripheral blood MUD transplant (n=57) at our center between June 2009 and April 2014. At 3 years post transplantation, the cumulative incidence (CI) of moderate to severe cGVHD was 44% following MUD versus 8% following CBT (P=0.0006) and CI of any cGVHD was 68% following MUD versus 32% following CBT (P=0.0017). Median time to being off immunosuppression among CB patients was 268 days versus not reached among MUD patients (P<0.0001). Late infections and late hospitalized days were reduced in CB patients (P=0.1 and <0.001, respectively). Three-year CI of transplant-related mortality (TRM) and relapse as well as 3-year overall survival (OS) were similar following CB and MUD transplantation. We demonstrate a significantly lower incidence of cGVHD, immunosuppression burden and late complication rate following UCB versus peripheral blood MUD transplant without decreased OS, increased relapse or early TRM. Combined with the rapid availability of UCB, these findings have led our center to move primarily to UCB over peripheral blood MUD when a MRD is not available.

High quality cord blood banking is feasible with delayed clamping practices. The eight-year experience and current status of the national Swedish Cord Blood Bank

The National Swedish Cord Blood Bank (NS-CBB) is altruistic and publicly funded. Herein we describe the status of the bank and the impact of delayed versus early clamping on cell number and volume. Cord Blood Units (CBUs) were collected at two University Hospitals in Sweden. Collected volume and nucleated cell content (TNC) were investigated in 146 consecutive Cord Blood (CB) collections sampled during the first quarter of 2012 and in 162 consecutive CB collections done in the first quarter of 2013, before and after clamping practices were changed from immediate to late (60 s) clamping. NS-CBB now holds close to 5000 units whereof 30 % are from non-Caucasian or mixed origins. Delayed clamping had no major effect on collection efficiency. The volume collected was slightly reduced (mean difference, 8.1 ml; 95 % CI, 1.3-15.0 ml; p = 0.02), while cell recovery was not (p = 0.1). The proportion of CBUs that met initial total TNC banking criteria was 60 % using a TNC threshold of 12.5 × 10(8), and 47 % using a threshold of 15 × 10(8) for the early clamping group and 52 and 37 % in the late clamping group. Following implementation of delayed clamping practices at NS-CBB; close to 40 % of the collections in the late clamping group still met the high TNC banking threshold and were eligible for banking, implicating that that cord blood banking is feasible with delayed clamping practices.

Robust Vaccine Responses in Adult and Pediatric Cord Blood Transplantation Recipients Treated for Hematologic Malignancies

Because cord blood (CB) lacks memory T and B cells and recent decreases in herd immunity to vaccine-preventable diseases in many developed countries have been documented, vaccine responses in CB transplantation (CBT) survivors are of great interest. We analyzed vaccine responses in double-unit CBT recipients transplanted for hematologic malignancies. In 103 vaccine-eligible patients, graft-versus-host disease (GVHD) most commonly precluded vaccination. Sixty-five patients (63%; engrafting units median HLA-allele match 5/8; range, 2 to 7/8) received protein conjugated vaccines, and 63 patients (median age, 34 years; range, .9 to 64) were evaluated for responses. Median vaccination time was 17 months (range, 7 to 45) post-CBT. GVHD (n = 42) and prior rituximab (n = 13) delayed vaccination. Responses to Prevnar 7 and/or 13 vaccines (serotypes 14, 19F, 23F) were seen in children and adults (60% versus 49%, P = .555). Responses to tetanus, diphtheria, pertussis, Haemophilus influenzae, and polio were observed in children (86% to 100%) and adults (53% to 89%) even if patients had prior GVHD or rituximab. CD4(+)CD45RA(+) and CD19(+) cell recovery significantly influenced tetanus and polio responses. In a smaller cohort responses were seen to measles (65%), mumps (50%), and rubella (100%) vaccines. No vaccine side effects were identified, and all vaccinated patients survived (median follow-up, 57 months). Although GVHD and rituximab can delay vaccination, CBT recipients (including adults and those with prior GVHD) have similar vaccine response rates to adult donor allograft recipients supporting vaccination in CBT recipients.

High Disease-Free Survival with Enhanced Protection against Relapse after Double-Unit Cord Blood Transplantation When Compared with T Cell-Depleted Unrelated Donor Transplantation in Patients with Acute Leukemia and Chronic Myelogenous Leukemia

Double-unit cord blood (DCB) grafts are a rapidly available stem cell source for adults with high-risk leukemias. However, how disease-free survival (DFS) after DCB transplantation (DCBT) compares to that of unrelated donor transplantation (URDT) is not fully established. We analyzed 166 allograft recipients (66 8/8 HLA-matched URDT, 45 7/8 HLA-matched URDT, and 55 DCBT) ages 16 to 60 years with high-risk acute leukemia or chronic myelogenous leukemia (CML). URDT and DCBT recipients were similar except DCBT recipients were more likely to have lower weight and non-European ancestry and to receive intermediate-intensity conditioning. All URDT recipients received a CD34(+) cell-selected (T cell-depleted) graft. Overall, differences between the 3-year transplantation-related mortality were not significant (8/8 URDT, 18%; 7/8 URDT, 39%; and DCBT, 24%; P = .108), whereas the 3-year relapse risk was decreased after DCBT (8/8 URDT, 23%; 7/8 URDT, 20%; and DCBT 9%, P = .037). Three-year DFS was 57% in 8/8 URDT, 41% in 7/8 URDT, and 68% in DCBT recipients (P = .068), and the 3-year DFS in DCBT recipients was higher than that of 7/8 URDT recipients (P = .021). In multivariate analysis in acute leukemia patients, factors adversely associated with DFS were female gender (hazard ratio [HR], 1.68; P = .031), diagnosis of acute lymphoblastic leukemia (HR, 2.09; P = .004), and 7/8 T cell-depleted URDT (HR, 1.91; P = .037). High DFS can be achieved in adults with acute leukemia and CML with low relapse rates after DCBT. Our findings support performing DCBT in adults in preference to HLA-mismatched T cell-depleted URDT and suggest DCBT is a readily available alternative to T cell-depleted 8/8 URDT, especially in patients requiring urgent transplantation.

Impact of the source of hematopoietic stem cell in unrelated transplants: comparison between 10/10, 9/10-HLA matched donors and cord blood

In absence of available matched-related or unrelated donor (MUD), mismatched unrelated donors (MMUD) and unrelated cord blood (UCB) are both considered to be suitable donors, with similar post-transplant overall survival. In most of these retrospective comparisons, HLA typing of adult donors was performed at eight loci. The aim of this study was to compare the outcome of patients transplanted from UCB (N = 64) with those transplanted from 9/10-HLA MMUD (N = 84) or 10/10-HLA MUD (N = 196). In multivariate analysis, UCB was associated with less Grade II-IV acute GVHD in comparison with MUD (aHR 1.97, 95% CI 1.19-3.27, P = 0.009) and MMUD transplants (aHR 1.79, 95% CI 1.02-3.15, P = 0.042), while the cumulative incidence of chronic GVHD was not significantly different between the three groups. Overall survival (OS), non-relapse mortality, and relapse were not different between MMUD and UCB transplantation, whereas OS was impaired after UCB in comparison with MUD (aHR 0.65, 95% CI 0.43-0.99, P = 0.043). Factors also impacting OS were the donor/recipient CMV serostatus (Donor-/Recipient+ aHR 1.76, 95% CI 1.23-2.52, P = 0.002 compared with D-/R-), the donor/recipient gender combination (Female/Male versus other combinations aHR 1.57, 95% CI 1.11-2.22, P = 0.012) and disease risk (aHR 1.58, 95% CI 1.05-2.38, P = 0.027 for high vs. low risk disease). Our data confirm that UCB and 9/10-HLA MMUD are both relevant alternative options when no 10/10-HLA donor is available. Donor/recipient gender combination and CMV serostatus had a significant impact on survival and may be taken into account, along with donor type, in the setting of MMUD and UCB transplants.

Impact of Allele-Level HLA Mismatch on Outcomes in Recipients of Double Umbilical Cord Blood Transplantation

The impact of allele-level HLA mismatch is uncertain in recipients of double umbilical cord blood (UCB) transplantation. We report a single-center retrospective study of the clinical effect of using allele-level HLA mismatch HLA-A, -B, -C, -DRB1, and -DQB1 of the 2 UCB units. We studied 342 patients with hematologic malignancy. Donor-recipient pairs were grouped according to the number of matched HLA alleles, with 32 matched at 9-10/10, 202 at 6-8/10, and 108 at 2-5/10 alleles. The incidence of hematopoietic recovery, acute and chronic graft-versus-host disease, and nonrelapse mortality and treatment failure was similar between groups. In an exploratory analysis of 174 patients with acute leukemia, after adjusting for length of first remission and cytogenetic risk group, a 2-5/10 HLA match was associated with lower risk of relapse and treatment failure. These data indicate that a high degree of allele-level HLA mismatch does not adversely affect transplant outcomes and may be associated with reduced relapse risk in patients with acute leukemia.

Risk Factors for Acute and Chronic Graft-versus-Host Disease after Allogeneic Hematopoietic Cell Transplantation with Umbilical Cord Blood and Matched Sibling Donors

Allogeneic hematopoietic cell transplantation is often complicated by graft-versus-host disease (GVHD). We analyzed the incidences and risk factors for acute (aGVHD) and chronic GVHD (cGVHD), and their impact on disease relapse and survival, among recipients of single umbilical cord blood (sUCB, n = 295), double umbilical cord blood (dUCB, n = 416), and matched sibling donor (MSD, n = 469) allografts. The incidences of grades II to IV aGVHD and chronic GVHD among dUCB, sUCB, and MSD were 56% and 26%, 26% and 7%, 37% and 40%, respectively. Development of aGVHD had no effect on relapse, nonrelapse mortality, or overall survival among cord blood recipients, but it was associated with worse nonrelapse mortality and survival in MSD recipients. Development of cGVHD was only associated with lower relapse in dUCBT. In multivariate analysis of GVHD incidence, age > 18 years was associated with higher incidence of aGVHD and cGVHD across all cohorts. In both UCB cohorts worse HLA match and prior aGVHD were associated with higher risks of aGVHD and cGVHD, respectively. Nonmyeloablative conditioning limited the risk of aGVHD compared with myeloablative conditioning in dUCB recipients. Cyclosporine A and mycophenolate mofetil as GVHD prophylaxis lowered the risk of cGVHD, compared with steroids with cyclosporine A, among sUCB recipients. This large contemporary analysis suggests distiinct risks and consequences of GVHD for UCB and MSD recipients. Limiting the severity of aGVHD remains important in all groups. Increasing the cord blood inventory or developing strategies that reduce the cell-dose threshold and thereby increase the chance of identifying an adequately dosed, better HLA-matched sUCB unit may further limit risks of aGVHD after UCB transplantation.

Association between Nondominant Unit Total Nucleated Cell Dose and Engraftment in Myeloablative Double-Unit Cord Blood Transplantation

Sustained hematopoiesis after double-unit cord blood transplantation (dCBT) is mediated by 1 unit in nearly all patients. To investigate the associations between nondominant unit characteristics and neutrophil engraftment, we studied 129 consecutive myeloablative dCBT recipients. Ninety-five percent (95% confidence interval, 90 to 98) of patients engrafted. Detection of the nondominant unit 21 to 28 days after dCBT was not associated with improved neutrophil engraftment. In univariate analyses, nondominant unit characteristics (infused total nucleated cell [TNC] and viable CD3(+) cell doses) were significantly associated with speed and success of neutrophil engraftment as were dominant unit characteristics (infused TNC; viable CD34(+), viable CD3(+), and viable CD3-56(+)16(+) cell doses; and post-thaw CD34(+) cell viability). In multivariate analysis, higher infused TNC dose of the nondominant unit was independently associated with improved neutrophil engraftment, even when this unit did not contribute to donor hematopoiesis. In further subgroup analysis, this association was only evident when the infused viable CD34(+) cell dose of the dominant unit was low (<1.20 × 10(5)/kg). These findings suggest nondominant units mediate a dose-dependent facilitation of engraftment in myeloablative dCBT and support continued investigation of dCBT biology and the clinical practice of dCBT in adults in whom low cell dose grafts are common.

Sufficient Immunosuppression with Thymoglobulin Is Essential for a Successful Haplo-Myeloid Bridge in Haploidentical-Cord Blood Transplantation

In haploidentical (haplo)-cord blood (CB) transplantations, early haplo donor engraftment serves as a myeloid bridge to sustainable CB engraftment and is associated with early neutrophil recovery. The conditioning regimens as published for haplo-cord protocols usually contain serotherapy, such as rabbit antithymocyte globulin (ATG) (Thymoglobulin, Genzyme, Cambridge, MA). However, reducing or omitting serotherapy is an important strategy to improve early immune reconstitution after transplantation. The need for serotherapy in successful haplo-cord transplantation, defined as having a haplo-derived myeloid bridge to CB engraftment, has not been investigated before. Two consecutive cohorts of patients underwent transplantation with haplo-CB. The first group underwent transplantation with haplo-CB for active infection and/or an underlying condition with expected difficult engraftment without a conventional donor available. They received a single unit (s) CB and haplo donor cells (CD34(+) selected, 5 × 10(6) CD34(+)/kg). The second cohort included patients with poor-risk malignancies, not eligible for other treatment protocols. They received a sCB and haplo donor cells (CD19/αβTCR-depleted; 5 × 10(6) CD34(+)/kg). Retrospectively in both cohorts, active ATG (Thymoglobulin) levels were measured and post-hematopoietic cell transplantation area under the curve (AUC) was calculated. The influence of ATG exposure for having a successful haplo-myeloid bridge (early haplo donor engraftment before CB engraftment and no secondary neutropenia) and transplantation-related mortality (TRM) were analyzed as primary endpoints. Twenty patients were included (16 in the first cohort and 4 in the second cohort). In 58% of evaluable patients, there was no successful haplo-derived myeloid bridge to CB engraftment, for which a low post-transplantation ATG exposure appeared to be a predictor (P <.001). TRM in the unsuccessful haplo-bridge group was 70% ± 16% versus 12% ± 12% in the successful haplo-bridge group (P = .012). In conclusion, sufficient in vivo T depletion with ATG is required for a successful haplo-myeloid bridge to CB engraftment.

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.

Stem cell comparison: what can we learn clinically from unrelated cord blood transplantation as an alternative stem cell source?

Allogeneic hematopoietic cell transplantation (HCT) is an important therapeutic option for a variety of malignant and non-malignant disorders (NMD). The use of umbilical cord blood transplantation (UCBT) has made HCT available to many more patients. The increased level of human leukocyte antigen disparity that can be tolerated makes UCBT a very attractive alternative source of hematopoietic stem cells; however, the increased risk of early death observed after UCBT remains an obstacle. Novel strategies such as ex vivo stem cell expansion are now becoming part of the standard clinical approach, and preliminary results are extremely encouraging with suggestion of reduction of early transplant-related mortality. Although there are no randomized studies that compare the risks and benefits of UCBT relative to those observed with related and unrelated donors both for malignant and NMD, several retrospective studies have compared outcomes between UCBT and other stem cell sources. In this review, we aim to describe and summarize the findings of the principal studies in this field. We hope that what we can learn from these studies and how we can use this information will improve the outcomes of HCT for patients with malignant and NMD.

Dominant unit CD34+ cell dose predicts engraftment after double-unit cord blood transplantation and is influenced by bank practice

We investigated the unit characteristics associated with engraftment after double-unit cord blood (CB) transplantation (dCBT) and whether these could be reliably identified during unit selection. Cumulative incidence of neutrophil engraftment in 129 myeloablative dCBT recipients was 95% (95% confidence interval: 90-98%). When precryopreservation characteristics were analyzed, the dominant unit CD34(+) cell dose was the only characteristic independently associated with engraftment (hazard ratio, 1.43; P = .002). When postthaw characteristics were also included, only dominant unit infused viable CD34(+) cell dose independently predicted engraftment (hazard ratio, 1.95; P < .001). We then examined the determinants of infused viable CD34(+) cell dose (precryopreservation count, postthaw recovery, and postthaw viability) in 402 units thawed at our center. This revealed close correlation between precryopreservation and postthaw CD34(+) cell counts (r(2) = 0.73). Median CD34(+) cell recovery was 101%, although it ranged from 12% to 1480%. Notably, units from non-Netcord Foundation for the Accreditation of Cellular Therapy (Netcord-FACT)-accredited banks were more likely to have low recovery (P < .001). Furthermore, although median postthaw CD34(+) cell viability was 92%, 33 (8%) units had <75% viable CD34(+) cells. Units from non-Netcord-FACT-accredited banks and units with cryovolumes other than 24.5 to 26.0 mL were more likely to have poor postthaw viability. Precryopreservation CD34(+) cell dose and banking practices should be incorporated into CB unit selection.

High day 28 ST2 levels predict for acute graft-versus-host disease and transplant-related mortality after cord blood transplantation

While cord blood transplantation (CBT) is an effective therapy for hematologic malignancies, acute graft-versus-host disease (aGVHD) is a leading cause of transplant-related mortality (TRM). We investigated if biomarkers could predict aGVHD and TRM after day 28 in CBT recipients. Day 28 samples from 113 CBT patients were analyzed. Suppressor of tumorigenicity 2 (ST2) was the only biomarker associated with grades II-IV and III-IV aGVHD and TRM. Day 180 grade III-IV aGVHD in patients with high ST2 levels was 30% (95% confidence interval [CI], 18-43) vs 13% (95% CI, 5-23) in patients with low levels (P = .024). The adverse effect of elevated ST2 was independent of HLA match. Moreover, high day 28 ST2 levels were associated with increased TRM with day 180 estimates of 23% (95% CI, 13-35) vs 5% (95% CI, 1-13) if levels were low (P = .001). GVHD was the most common cause of death in high ST2 patients. High concentrations of tumor necrosis factor receptor-1, interleukin-8, and regenerating islet-derived protein 3-α were also associated with TRM. Our results are consistent with those of adult donor allografts and warrant further prospective evaluation to facilitate future therapeutic intervention to ameliorate severe aGVHD and further improve survival after CBT.

The role of the thymus in T-cell immune reconstitution after umbilical cord blood transplantation

Umbilical cord blood (UCB) is an alternative source of hematopoietic stem cells for patients without HLA-matched adult donors. UCB contains a low number of nucleated cells and mostly naive T cells, resulting in prolonged time to engraftment and lack of transferred T-cell memory. Although the first phase of T-cell reconstitution after UCB transplantation (UCBT) depends on peripheral expansion of transferred T cells, permanent T-cell reconstitution is mediated via a central mechanism, which depends on de novo production of naive T lymphocytes by the recipient's thymus from donor-derived lymphoid-myeloid progenitors (LMPs). Thymopoiesis can be assessed by quantification of recent thymic emigrants, T-cell receptor excision circle levels, and T-cell receptor repertoire diversity. These assays are valuable tools for monitoring posttransplantation thymic recovery, but more importantly they have shown the significant prognostic value of thymic reconstitution for clinical outcomes after UCBT, including opportunistic infections, disease relapse, and overall survival. Strategies to improve thymic entry and differentiation of LMPs and to accelerate recovery of the thymic stromal microenvironment may improve thymic lymphopoiesis. Here, we discuss the mechanisms and clinical implications of thymic recovery and new approaches to improve reconstitution of the T-cell repertoire after UCBT.

Rapid induction of single donor chimerism after double umbilical cord blood transplantation preceded by reduced intensity conditioning: results of the HOVON 106 phase II study

Double umbilical cord blood transplantation is increasingly applied in the treatment of adult patients with high-risk hematological malignancies and has been associated with improved engraftment as compared to that provided by single unit cord blood transplantation. The mechanism of improved engraftment is, however, still incompletely understood as only one unit survives. In this multicenter phase II study we evaluated engraftment, early chimerism, recovery of different cell lineages and transplant outcome in 53 patients who underwent double cord blood transplantation preceded by a reduced intensity conditioning regimen. Primary graft failure occurred in one patient. Engraftment was observed in 92% of patients with a median time to neutrophil recovery of 36 days (range, 15-102). Ultimate single donor chimerism was established in 94% of patients. Unit predominance occurred by day 11 after transplantation and early CD4(+) T-cell chimerism predicted for unit survival. Total nucleated cell viability was also associated with unit survival. With a median follow up of 35 months (range, 10-51), the cumulative incidence of relapse and non-relapse mortality rate at 2 years were 39% and 19%, respectively. Progressionfree survival and overall survival rates at 2 years were 42% (95% confidence interval, 28-56) and 57% (95% confidence interval, 43-70), respectively. Double umbilical cord blood transplantation preceded by a reduced intensity conditioning regimen using cyclophosphamide/fludarabine/4 Gy total body irradiation results in a high engraftment rate with low non-relapse mortality. Moreover, prediction of unit survival by early CD4(+) lymphocyte chimerism might suggest a role for CD4(+) lymphocyte mediated unit-versus-unit alloreactivity. www.trialregister.nl NTR1573.

Human herpesvirus 6 reactivation before engraftment is strongly predictive of graft failure after double umbilical cord blood allogeneic stem cell transplantation in adults

Our main objective was to determine new factors associated with engraftment and single-unit predominance after double umbilical cord blood (UCB) allogeneic stem-cell transplantation. Engraftment occurred in 78% of cases in this retrospective study including 77 adult patients. Three-year overall survival, disease-free survival, relapse incidence, and nonrelapse mortality were 55 ± 6%, 44 ± 6%, 33 ± 5%, and 23 ± 4%, respectively. In multivariate analysis, Human herpesvirus 6 reactivation during aplasia (hazard ratio [HR] = 2.63; 95% confidence interval [CI]: 1.64-4.17; p < 0.001), younger recipient age (<53 years) (HR = 1.97; 95% CI: 1.16-3.35; p = 0.012), and lower human leukocyte antigen matching between the two units (3 of 6 or 4 of 6) (HR = 2.09; 95% confidence interval: 1.22-3.59; p = 0.013) were the three factors independently associated with graft failure. Also, factors independently predicting the losing UCB unit were younger age of the UCB unit (odds ratio [OR] = 1.01; 95% CI: 1-1.02; p = 0.035), lower CD34(+) cell dose contained in the UCB unit (≤ 0.8 × 10(5)/kg) (OR = 2.55; 95% CI: 1.05-6.16; p = 0.04), and presence of an ABO incompatibility between the UCB unit and the recipient (OR = 2.53; 95% CI: 1.15-5.53; p = 0.02). Thus, Human herpesvirus 6 reactivation during aplasia, lower unit-unit human leukocyte antigen matching, and younger UCB unit age, as new unfavorable predictive factors, may represent new parameters to take into account after double UCB allogeneic stem-cell transplantation in adults. These results need to be confirmed prospectively, as they may influence unit selections and patient outcomes.

IL-12-secreting CD19-targeted cord blood-derived T cells for the immunotherapy of B-cell acute lymphoblastic leukemia

Disease relapse or progression is a major cause of death following umbilical cord blood (UCB) transplantation (UCBT) in patients with high-risk, relapsed or refractory acute lymphoblastic leukemia (ALL). Adoptive transfer of donor-derived T cells modified to express a tumor-targeted chimeric antigen receptor (CAR) may eradicate persistent disease after transplantation. Such therapy has not been available to UCBT recipients, however, due to the low numbers of available UCB T cells and the limited capacity for ex vivo expansion of cytolytic cells. We have developed a novel strategy to expand UCB T cells to clinically relevant numbers in the context of exogenous cytokines. UCB-derived T cells cultured with interleukin (IL)-12 and IL-15 generated >150-fold expansion with a unique central memory/effector phenotype. Moreover, UCB T cells were modified to both express the CD19-specific CAR, 1928z, and secrete IL-12. 1928z/IL-12 UCB T cells retained a central memory-effector phenotype and had increased antitumor efficacy in vitro. Furthermore, adoptive transfer of 1928z/IL-12 UCB T cells resulted in significantly enhanced survival of CD19(+) tumor-bearing SCID-Beige mice. Clinical translation of CAR-modified UCB T cells could augment the graft-versus-leukemia effect after UCBT and thus further improve disease-free survival of transplant patients with B-cell ALL.

Donor-recipient allele-level HLA matching of unrelated cord blood units reveals high degrees of mismatch and alters graft selection

The feasibility of selecting cord blood (CB) units at high-resolution HLA match has not been investigated. We analyzed the high-resolution donor-recipient HLA match of 100 double-unit 4-6/6 HLA-A,-B antigen, -DRB1 allele-matched CB grafts (units 1a and 1b) and their back-up units (n=377 units in total). The median cryopreserved graft dose was 2.9 × 10(7)/kg/unit, and at high resolution these units had a median donor-recipient HLA-allele match of 5/8 (range 2-8/8) and 6/10 (range 2-9/10), respectively. We then evaluated how often use of high-resolution HLA-match criteria would change the original graft selection to substitute one or both of the back-up units for units 1a and/or 1b. On using a model in which both a higher eight-allele HLA match and a cell dose ⩾ 2.0 × 10(7)/kg/unit were required, graft selection changed in 33% of transplants with minimal effect on cell dose (8.3% reduction). In summary, while units chosen based on HLA-A,-B antigen and -DRB1 allele match have substantial mismatch at higher resolution, CB selection based on high-resolution HLA match is possible in a significant proportion of patients without compromise in cell dose.

Second cancers and late mortality in Australian children treated by allogeneic HSCT for haematological malignancy

We examined risk of second cancer and late mortality in a population-based Australian cohort of 717 pediatric allogeneic stem cell transplant (HSCT) recipients treated for a malignant disease during 1982-2007. Record linkage with population-based death and cancer registries identified 17 second cancers at a median of 7.9 years post HSCT; thyroid cancer being the most common malignancy (n=8). The cumulative incidence of second cancer was 8.7% at follow-up, and second cancers occurred 20 times more often than in the general population (standardised incidence ratio 20.3, 95% confidence interval (CI)=12.6-32.7). Transplantation using radiation-based conditioning regimens was associated with increased second cancer risk. A total of 367 patients survived for at least 2 years post HSCT and of these 44 (12%) died at a median of 3.1 years after HSCT. Relapse was the most common cause of late mortality (n=32). The cumulative incidence of late mortality was 14.7%. The observed rate of late mortality was 36 times greater than in the matched general population (standardised mortality ratio 35.9, 95% CI=26.7-48.3). Recipients who relapsed or who had radiation-based conditioning regimens were at higher risk of late mortality. Second cancers and late mortality continue to be a risk for pediatric patients undergoing HSCT, and these results highlight the need for effective screening and survivorship programs.

Poor outcome with nonmyeloablative conditioning regimen before cord blood transplantation for patients with high-risk acute myeloid leukemia compared with matched related or unrelated donor transplantation

Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) is recommended for patients with high-risk acute myeloid leukemia (AML). In many situations, a matched related (MRD) or matched unrelated donor (MUD) is lacking, in which case unrelated cord blood units (UCB) provide an alternative. We analyzed the outcome of consecutive high-risk AML patients prepared with reduced-intensity conditioning (RIC) regimens and allografted with UCB (n = 32) and compared their outcome with high-risk AML patients who underwent transplantation with MRD/MUD (n = 49) in the same period of time. Grade III to IV acute graft-versus-host disease (GVHD) occurred slightly more frequently in the UCB group (25%) than in the MRD/MUD group (8%) (P = .069). Conversely, we found a lower incidence of extensive chronic GVHD in the UCB group (6%) than in the MRD/MUD group (20%, P = .085). Nonrelapse mortality at 4 years was 16% and 22% in the UCB and MRD/MUD groups, respectively (P = .529). The cumulative incidence of relapse at 4 years was significantly higher in the UCB group (60%) than in the MRD/MUD group (27%, P = .006). Leukemia-free survival (LFS) and overall survival (OS) at 4 years were 25% and 34%, respectively, in the UCB group and 50% and 56%, respectively, in the MRD/MUD group (LFS, P = .029; OS, P = .072). Multivariate analyses adjusted by cytogenetics and disease status at the time of Allo-HSCT revealed that use of UCB remained an independent predictive factor of shorter LFS (hazard ratio, 2.0; 95% confidence interval, 1.1 to 3.6; P = .018), and was associated with a trend for shorter OS (hazard ratio, 1.7; 95% confidence interval, .9 to 3.2; P = .093). Whereas UCB provides an alternative for patients with high-risk AML lacking an MRD/MUD, the high incidence of relapse after RIC-based UCB Allo-HSCT is a concern. Attempts to improve leukemic control with UCB Allo-HSCT are warranted, as well as the evaluation of other alternative donors in this context.

Frequent human herpesvirus-6 viremia but low incidence of encephalitis in double-unit cord blood recipients transplanted without antithymocyte globulin

Cord blood transplantation (CBT) is a known risk factor for human herpesvirus-6 (HHV-6) infection. We analyzed the nature of HHV-6 infections in 125 double-unit CBT recipients (median age, 42 years) transplanted for hematologic malignancies with calcineurin inhibitor/mycophenolate mofetil prophylaxis and no antithymocyte globulin. One hundred seventeen patients (94%) reactivated HHV-6 by quantitative plasma PCR (median peak, 7600 copies/mL; range, 100 to 160,000) at a median of 20 days (range, 10 to 59) after transplantation. HHV-6 encephalitis occurred in 2 patients (1.6%), of whom 1 died and 1 recovered with therapy. No association was found between high-level HHV-6 viremia (≥10,000 or ≥25,000 copies/mL) and age, diagnosis, conditioning intensity, or dominant unit characteristics or between high-level viremia and transplant outcomes (engraftment, cytomegalovirus reactivation, day 100 grades II to IV acute graft-versus-host disease, day 100 transplant-related mortality, or 1-year disease-free survival). HHV-6 therapy delayed the onset of cytomegalovirus reactivation. Interestingly, HHV-6 resolution was observed in untreated patients, and resolution of viremia correlated with absolute lymphocyte count recovery. We observed a low incidence of encephalitis and no association with CBT outcomes. Our data suggest therapy in uncomplicated viremia may not be warranted. However, further investigation of the risk-to-benefit of HHV-6 viremia treatment and standardization of PCR testing is required.

Long-term immune reconstitution and infection burden after mismatched hematopoietic stem cell transplantation

Mismatched unrelated donor (MMUD) or umbilical cord blood (UCB) can be chosen as alternative donors for allogeneic stem cell transplantation but might be associated with long-lasting immune deficiency. Sixty-six patients who underwent a first transplantation from either UCB (n = 30) or 9/10 MMUD (n = 36) and who survived beyond 3 months were evaluated. Immune reconstitution was prospectively assessed at sequential time points after transplantation. NK, B, CD4(+), and CD8(+) T cells and their naïve and memory subsets, as well as regulatory T cells (Treg), were studied. Detailed analyses on infections occurring after 3 months were also assessed. The 18-month cumulative incidences of infection-related death were 8% and 3%, and of infections were 72% and 57% after MMUD and UCB transplantation, respectively. Rates of infection per 12 patient-month were roughly 2 overall (1 for bacterial, .9 for viral, and .3 for fungal infections). Memory, naïve CD4(+) and CD8(+)T cells, naïve B cells, and Treg cells reconstitution between the 2 sources were roughly similar. Absolute CD4(+)T cells hardly reached 500 per μL by 1 year after transplantation and most B cells were of naïve phenotype. Correlations between immune reconstitution and infection were then performed by multivariate analyses. Low CD4(+) and high CD8(+)T cells absolute counts at 3 months were linked to increased risks of overall and viral (but not bacterial) infections. When assessing for the naïve/memory phenotypes at 3 months among the CD4(+) T cell compartment, higher percentages of memory subsets were protective against late infections. Central memory CD4(+)T cells protected against overall and bacterial infections; late effector memory CD4(+)T cells protected against overall, bacterial, and viral infections. To the contrary, high percentage of effector- and late effector-memory subsets at 3 months among the CD8(+) T cell compartment predicted higher risks for viral infections. Patients who underwent transplantation from alternative donors represent a population with very high risk of infection. Detailed phenotypic analysis of immune reconstitution may help to evaluate infection risk and to adjust infection prophylaxis.

Optimal stem cell source for allogeneic stem cell transplantation for hematological malignancies

Hematopoietic stem cell transplant (HSCT) is a standard treatment for many hematological malignancies. Three different sources of stem cells, namely bone marrow (BM), peripheral blood stem cells (PBSC) and cord blood (CB) can be used for HSCT, and each has its own advantages and disadvantages. Randomized controlled trials (RCTs) suggest that there is no significant survival advantage of PBSC over BM in Human Leukocyte Antigen-matched sibling transplant for adult patients with hematological malignancies. PBSC transplant probably results in lower risk of relapse and hence better disease-free survival, especially in patients with high risk disease at the expense of higher risks of both severe acute and chronic graft-versus-host disease (GVHD). In the unrelated donor setting, the only RCT available suggests that PBSC and BM result in comparable overall and disease-free survivals in patients with hematological malignancies; and PBSC transplant results in lower risk of graft failure and higher risk of chronic GVHD. High level evidence is not available for CB in comparison to BM or PBSC. The risks and benefits of different sources of stem cells likely change with different conditioning regimen, strategies for prophylaxis and treatment of GVHD and manipulation of grafts. The recent success and rapid advance of double CB transplant and haploidentical BM and PBSC transplants further complicate the selection of stem cell source. Optimal selection requires careful weighing of the risks and benefits of different stem cell source for each individual recipient and donor. Detailed counseling of patient and donor regarding risks and benefits in the specific context of the patient and transplant method is essential for informed decision making.

Complement fragment 3a priming of umbilical cord blood progenitors: safety profile

Preclinical data showed that priming CD34(+) hematopoietic progenitor cells with complement fragment 3a (C3a) improved homing and engraftment. Thus, we hypothesized that priming of umbilical cord blood (UCB) hematopoietic progenitors with C3a would facilitate homing and could potentially be used to address the need for improved engraftment after UCB transplantation. We primed 1 of 2 UCB units for double UCB transplantation after nonmyeloablative conditioning. This design provided adequate safety and the potential to observe skewed long-term chimerism in favor of the C3a-primed unit as a surrogate measure of efficacy. C3a priming of 1 UCB unit did not result in infusional toxicity. Increased grades 1 to 3 hypertension were the only infusional adverse events observed in 9 (30%) patients. We observed no activation of inflammatory or coagulation pathways downstream of C3a. As tested, C3a priming did not impair engraftment, but did not skew chimerism toward the treated unit. As compared with historical controls, mortality and survival were not adversely affected. Thus, before any additional clinical studies, C3a priming to promote engraftment will require further preclinical optimization.

Comparison of unrelated cord blood transplantation and HLA-matched sibling hematopoietic stem cell transplantation for patients with chronic myeloid leukemia in advanced stage

This is the first report to present a clinical comparison of unrelated cord blood transplantation (CBT) and HLA-matched sibling allogeneic hematopoietic stem cell transplantation for patients with chronic myeloid leukemia (CML) in advanced stage (accelerated phase or blast crisis). A total of 32 consecutive patients with advanced CML received unrelated CBT (n= 16) or HLA-matched sibling allogeneic peripheral blood stem cell or bone marrow transplantation (allo-PBSCT/BMT) (n = 16) between 2002 and 2011. The median day to neutrophil engraftment and the median day to platelet engraftment were longer in the unrelated CBT group. The cumulative incidence of grades 1 to 2 acute graft-versus-host disease (aGVHD), grades 3 to 4 aGVHD, and chronic graft-versus-host disease did not differ significantly between the 2 cohorts. The cumulative incidence of transplantation-related mortality (TRM) at day +180 was higher in CBT group (37.5% versus 12.5%, P = .013). The risk of relapse was lower in CBT patients compared with that of allo-PBSCT/BMT patients (14.2% versus 42.7%, P = .03). The long-term survival in CBT group patients was slightly better than that of allo-PBSCT/BMT group, although the difference did not reach statistical significance: the 5-year overall survival for CBT patients and allo-PBSCT/BMT patients was 62.5% and 48.6%, respectively (P= .10), whereas the 5-year leukemia-free-survival rate was 50% and 40.5%, respectively (P = .12). Our comparisons suggest that patients with advanced CML receiving unrelated CBT had a lower relapse rate, a slightly better long-term survival, but a higher early TRM than those receiving HLA-matched related allo-PBSCT/BMT.

Alternative transplant donor sources: is there any consensus?

PURPOSE OF REVIEW

To review the data supporting the use of alternative donors for hematopoietic cell transplantation of patients with high-risk or advanced hematological malignancies.

RECENT FINDINGS

Advances in supportive therapy and technology have improved the safety and efficacy of alternative donors for hematopoietic cell transplantation. Molecular techniques have allowed for better human leukocyte antigen matching of unrelated adult donors. Novel strategies such as adoptive regulatory T cells or posttransplantation cyclophosphamide contributed to better outcomes after partially matched related donors. In umbilical cord blood transplantation, the ability to find adequately dosed single-unit grafts, the utilization of double-unit grafts, and novel methodologies such as ex-vivo expansion, intrabone injection, and priming to accelerate engraftment are promising. Available retrospective studies suggest despite the differences in hematopoietic recovery, risk of graft-versus-host disease, and relapse, long-term outcomes are similar between different alternative donor types.

SUMMARY

In the absence of a suitable matched related donor, most patients will be able to find an alternative donor to proceed to a potentially curative allogeneic transplantation. Emerging new technologies will further improve the safety and efficacy of alternative donor transplantation. Ongoing and future randomized studies will better define the relative efficacy of alternative donor types.

Double umbilical cord blood transplantation for hematological malignancies: a long-term analysis from the SFGM-TC registry

Allogeneic hematopoietic stem cell (HSC) transplantation is a curative treatment for many hematologic malignancies for which umbilical cord blood (UCB) represents an alternative source of HSCs. To overcome the low cellularity of one UCB unit, double UCB transplantation (dUCBT) has been developed in adults. We have analyzed the outcome of 136 patients who underwent dUCBT reported to the SFGM-TC registry between 2005 and 2007. Forty-six patients received myeloablative regimens, and 90 patients received reduced-intensity conditioning regimens. There were 84 cases of leukemia, 17 cases of non-Hodgkin lymphoma, 11 cases of myeloma, and 24 other hematologic malignancies. At transplantation, 40 (29%) patients were in complete remission. At day 60 after transplantation, the cumulative incidence of neutrophil recovery was 91%. We observed one UCB unit domination in 88% of cases. The cumulative incidence of day 100 acute graft-versus-host disease, chronic graft-versus-host disease, transplant-related mortality, and relapse at 2 years were 36%, 23%, 27%, and 28% respectively. After a median follow-up of 49.5 months, the 3-year probabilities of overall and progression-free survival were 41% and 35%, respectively, with a significant overall survival advantage when male cord engrafted male recipients. We obtained a long-term plateau among patients in complete remission, which makes dUCBT a promising treatment strategy for these patients.

Umbilical cord blood transplantation: the first 25 years and beyond

Umbilical cord blood is an alternative hematopoietic stem cell source for patients with hematologic diseases who can be cured by allogeneic hematopoietic cell transplantation. Initially, umbilical cord blood transplantation was limited to children, given the low cell dose infused. Both related and unrelated cord blood transplants have been performed with high rates of success for a variety of hematologic disorders and metabolic storage diseases in the pediatric setting. The results for adult umbilical cord blood transplantation have improved, with greater emphasis on cord blood units of sufficient cell dose and human leukocyte antigen match and with the use of double umbilical cord blood units and improved supportive care techniques. Cord blood expansion trials have recently shown improvement in time to engraftment. Umbilical cord blood is being compared with other graft sources in both retrospective and prospective trials. The growth of the field over the last 25 years and the plans for future exploration are discussed.

Quantitative assessment of T cell repertoire recovery after hematopoietic stem cell transplantation

Delayed T-cell recovery and restricted T-cell receptor (TCR) diversity after allogeneic hematopoietic stem cell transplantation (allo-HSCT) are associated with increased risks of infection and cancer relapse. Technical challenges have limited faithful measurement of TCR diversity following allo-HSCT. Here we combined 5′-RACE PCR with deep sequencing, to quantify TCR diversity in 28 allo-HSCT recipients using a single oligonucleotide pair. Analysis of duplicate blood samples confirmed that the frequency of individual TCRs was accurately determined. After 6 months, cord blood graft recipients approximated the TCR diversity of healthy individuals, whereas recipients of T-cell-depleted peripheral blood stem cell grafts had a 28-fold and 14-fold lower CD4⁺ and CD8⁺ T-cell diversity, respectively. After 12 months, these deficiencies had improved for the CD4⁺, but not the CD8⁺ T-cell compartment. Overall, this method provides unprecedented views of T-cell repertoire recovery after allo-HSCT and may identify patients at high risk of infection or relapse.

Graft-versus-host disease after double-unit cord blood transplantation has unique features and an association with engrafting unit-to-recipient HLA match

Manifestations of and risk factors for graft-versus-host disease (GVHD) after double-unit cord blood transplantation (DCBT) are not firmly established. We evaluated 115 DCBT recipients (median age, 37 years) who underwent transplantation for hematologic malignancies with myeloablative or nonmyeloablative conditioning and calcineurin inhibitor/mycophenolate mofetil immunosuppression. Incidence of day 180 grades II to IV and III to IV acute GVHD (aGVHD) were 53% (95% confidence interval, 44 to 62) and 23% (95% confidence interval, 15 to 31), respectively, with a median onset of 40 days (range, 14 to 169). Eighty percent of patients with grades II to IV aGVHD had gut involvement, and 79% and 85% had day 28 treatment responses to systemic corticosteroids or budesonide, respectively. Of 89 engrafted patients cancer-free at day 100, 54% subsequently had active GVHD, with 79% of those affected having persistent or recurrent aGVHD or overlap syndrome. Late GVHD in the form of classic chronic GVHD was uncommon. Notably, grades III to IV aGVHD incidence was lower if the engrafting unit human leukocyte antigen (HLA)-A, -B, -DRB1 allele match was >4/6 to the recipient (hazard ratio, 0.385; P = .031), whereas engrafting unit infused nucleated cell dose and unit-to-unit HLA match were not significant. GVHD after DCBT was common in our study, predominantly affected the gut, and had a high therapy response, and late GVHD frequently had acute features. Our findings support the consideration of HLA- A,-B,-DRB1 allele donor-recipient (but not unit-unit) HLA match in unit selection, a practice change in the field. Moreover, new prophylaxis strategies that target the gastrointestinal tract are needed.

A novel reduced-intensity conditioning regimen induces a high incidence of sustained donor-derived neutrophil and platelet engraftment after double-unit cord blood transplantation

A preparative regimen of reduced intensity that can reliably engraft cord blood (CB) and can be used as an alternative to either high-dose myeloablative or nonmyeloablative conditioning is needed. We evaluated double-unit CB transplantation in 30 patients (median age, 56 years; range, 18 to 69) with acute leukemia or myelodysplasia using a regimen of cyclophosphamide 50 mg/kg, fludarabine 150 mg/m(2), thiotepa 10 mg/kg, and 400 cGy total body irradiation with cyclosporine-A/mycophenolate mofetil immunosuppression. Ninety-seven percent of patients engrafted at a median of 26 days (range, 13 to 43), and 93% of patients had recovered platelets by day 180. Grades II to IV acute graft-versus-host disease (GVHD) incidence was 67% at day 180, and chronic GVHD was 10% at 1 year. Transplant-related mortality was 20% at day 180, and relapse was 11% at 2 years. Overall, 2-year disease-free survival (DFS) was 60% at 2 years. A hierarchy in DFS was seen according to the Sorror comorbidity score: 11 patients (median age, 55 years) with a score of 1 had a 2-year DFS of 82% compared with 62% in 9 patients (median age, 51 years) with a score of 2 to 3 and 40% in 11 patients (median age, 58 years) with a score of 4 to 5 (P = .13). This reduced-intensity regimen combined with double-unit CB transplantation reliably facilitates sustained donor engraftment without antithymocyte globulin. Although other approaches are needed in patients with high comorbidity scores, this regimen is highly effective in patients ≥50 years old who are otherwise reasonably fit. It also represents a promising alternative to high-dose conditioning in younger patients.