Factors affecting mortality following myeloablative cord blood transplantation in adults: a pooled analysis of three international registries

Lymphocyte Crossmatch Testing or Donor HLA-DP and -DQ Allele Typing Effectiveness in Single Cord Blood Transplantation for Patients With Anti-HLA Antibodies Other Than Against HLA-A, -B, -C, and -DRB1

Anti-human leukocyte antigen (HLA) antibodies other than those against HLA-A, -B, -C, and DRB1 are a risk factor for engraftment delay and failure, especially in cord blood transplantation (CBT). The primary objective of this study was to assess the impact of the presence of anti-HLA antibodies on CBT and to evaluate the utility of lymphocyte crossmatch testing or additional HLA-DP and -DQ typing of CB units in improving transplant outcomes. We retrospectively assessed the engraftment rates and transplant outcomes of 772 patients who underwent their first CBT at our hospital between 2012 and 2021. Donors were routinely typed for HLA-A, -B, -C, and-DRB1 alleles, and the anti-HLA antibodies of recipients were screened before donor selection in all cases. Among patients who had antibodies against other than HLA-A, -B, -C, and DRB1 (n = 58), lymphocyte crossmatch testing (n = 32) or additional HLA-DP/-DQ alleles typing of CB (n = 15) was performed to avoid the use of units with corresponding alleles. The median patient age was 57 years (16 to 77). Overall, 75.7% had a high-risk disease status at transplantation, 83.5% received myeloablative conditioning regimens, and >80% were heavily transfused. Two hundred twenty-nine of the 772 recipients (29.6%) were positive for anti-HLA antibodies. There were no statistical differences in the number of infused CD34-positive cells between the anti-HLA antibody-positive and the anti-HLA antibody-negative patients. Of the 229 patients with anti-HLA antibodies, 168 (73.3%) had antibodies against HLA-A, -B, -C, and-DRB1 (Group A), whereas 58 (25.3%) had antibodies against HLA-DP, HLA-DQ, or -DRB3/4/5 with or without antibodies against HLA-A, -B, -C, and -DRB1 (Group B). No patients in both Groups A and B exhibited donor-specific anti-HLA antibodies against HLA-A, -B, -C, and -DRB1. The neutrophil engraftment rate was lower in patients with anti-HLA antibodies than in those without antibodies (89.9% versus 94.1%), whereas nonrelapse mortality (NRM) before engraftment was higher in antibody-positive patients (9.6% versus 4.9%). In patients who received 2 or more HLA allele-mismatched CB in the host-versus-graft (HVG) direction (n = 685), the neutrophil engraftment rate was lower in the anti-HLA antibody-positive recipients than in the antibody-negative recipients with significant differences (88.8% versus 93.8%) (P = .049). Similarly, transplant outcomes were worse in the antibody-positive patients with respect to 2-year overall survival (OS) (43.1% versus 52.3%) and NRM (44.0% versus 30.7%) than in the antibody-negative patients. In contrast, the results of Group B were comparable to those of the antibody-negative patients, while those of Group A were statistically worse than the antibody-negative patients in terms of all engraftment rate (88.6%), OS (34.2%), and NRM (49.0%). The presence of anti-HLA antibodies negatively impacts engraftment, NRM, and OS in CBT. However, HLA-DP/-DQ allele typing of CB units or lymphocyte crossmatch testing could be a useful strategy to overcome poor engraftment rates and transplant outcomes, especially in patients with anti-HLA antibodies against HLA-DP, HLA-DQ, or -DRB3/4/5.

Unrelated female-to-male bone marrow transplantation would be preferred over cord blood transplantation in male patients

BACKGROUND AIMS

Allogeneic hematopoietic stem cell transplantation from female donors to male recipients (female-to-male allo-HCT) is a well-established risk factor for a greater incidence of non-relapse mortality (NRM) and chronic graft-versus-host disease (GVHD). In contrast, unrelated cord blood transplantation (UCBT) is associated with a lower incidence of chronic GVHD. In this study, survival outcomes were compared between the UCBT and unrelated female-to-male bone marrow transplantation (UFMBMT) groups.

METHODS

We evaluated male allo-HCT recipients who underwent UCBT or UFMBMT between 2012 and 2020 in Japan. There were 2517 cases in the UCBT group, 456 cases in the HLA-matched UFMBMT group and 457 cases in the HLA-mismatched UFMBMT group.

RESULTS

HLA-mismatched UFMBMT was significantly associated with a decreased risk of relapse (hazard ratio [HR] 0.74; 95% confidence interval [CI] 0.57-0.98], P = 0.033) and HLA-matched UFMBMT had the tendency of a decreased risk of relapse (HR 0.78; 95% CI 0.61-1.01, P = 0.059). HLA-matched UFMBMT was also associated with favorable OS (HR 0.82; 95% CI 0.69-0.97, P = 0.021). The relationship between the donor sources and relapse was similarly observed in the lymphoid malignancy cohort.

CONCLUSIONS

The difference of graft-versus leukemia effect by H-Y immunity according to donor sources might contribute to the difference in clinical impact. It might be desirable for patients who could sufficiently wait for donor coordination to select BMT rather than UCBT, even if only unrelated female donors are available for male recipients.

A predictive model combining clinical characteristics and nutritional risk factors for overall survival after umbilical cord blood transplantation

BACKGROUND

Umbilical cord blood transplantation (UCBT) is a curable therapy for hematological disease; however, the impact of nutritional status on UCBT outcomes remains controversial. To evaluate the joint effect of clinical characteristics and nutritional status on the prognosis of patients who underwent UCBT, we screened various factors to establish a predictive model of overall survival (OS) after UCBT.

METHODS

We performed an integrated clinical characteristic and nutritional risk factor analysis and established a predictive model that could be used to identify UCBT recipients with poor OS. Internal validation was performed by using the bootstrap method with 500 repetitions.

RESULTS

Four factors, including disease status, conditioning regimen, calf skinfold thickness and albumin level, were identified and used to develop a risk score for OS, which showed a positive predictive value of 84.0%. A high-risk score (≥ 2.225) was associated with inferior 3-year OS post-UCBT [67.5% (95% CI 51.1-79.4%), P = 0.001]. Then, we built a nomogram based on the four factors that showed good discrimination with a C-index of 0.833 (95% CI 0.743-0.922). The optimism-corrected C-index value of the bootstrapping was 0.804. Multivariate analysis suggested that a high calf skinfold thickness (≥ 20.5 mm) and a low albumin level (< 33.6 g/L) conferred poor disease-free survival (DFS).

CONCLUSION

The predictive model combining clinical and nutritional factors could be used to predict OS in UCBT recipients, thereby promoting preemptive treatment.

Novel Human Umbilical Di-Chimeric (HUDC) cell therapy for transplantation without life-long immunosuppression

Background

Cell-based therapies are promising for tolerance induction in bone marrow (BM), solid organs, and vascularized composite allotransplantation (VCA). The toxicity of bone marrow transplantation (BMT) protocols precludes this approach from routine clinical applications. To address this problem, we developed a new therapy of Human Umbilical Di-Chimeric (HUDC) cells for tolerance induction in transplantation. This study established in vitro characterization of the created HUDC cells.

Methods

We performed sixteen ex vivo polyethylene glycol (PEG)-mediated fusions of human umbilical cord blood (UCB) cells from two unrelated donors. Fusion feasibility was confirmed in vitro by flow cytometry (FC) and confocal microscopy (CM). The HUDC cells' genotype was assessed by lymphocytotoxicity test and short tandem repeat-polymerase chain reaction (STR-PCR) analysis, phenotype by FC, viability by LIVE/DEAD® assay, and apoptosis level by Annexin V staining. We used COMET assay to assess HUDC cells' genotoxicity after the fusion procedure. Clonogenic properties of HUDC cells were evaluated by colony forming unit (CFU) assay. Mixed lymphocyte reaction (MLR) assay assessed immunogenic and tolerogenic properties of HUDC cells.

Results

We confirmed the creation of HUDC cells from two unrelated human donors of UCB cells by FC and CM. Human leukocyte antigen (HLA) class I and II typing, and STR-PCR analysis of HUDC cells confirmed the presence of alleles and loci from both unrelated UCB donors (donor chimerism: 49%±8.3%, n=4). FC confirmed the hematopoietic phenotype of HUDC cells. We confirmed high HUDC cells' viability (0.47% of dead cells) and a low apoptosis level of fused HUDC cells (15.9%) compared to positive control of PKH-stained UCB cells (20.4%) before fusion. COMET assay of HUDC cells revealed a lack of DNA damage. CFU assay confirmed clonogenic properties of HUDC cells, and MLR assay revealed a low immunogenicity of HUDC cells.

Conclusions

This study confirmed creation of a novel HUDC cell line by ex vivo PEG-mediated fusion of UCB cells from two unrelated donors. The unique concept of creating a HUDC cell line, representing the genotype and phenotype of both, transplant donor and the recipient, introduces a promising approach for tolerance induction in BM, solid organs, and VCA transplantation.

Effect of multiple HLA-locus mismatches on outcomes after single cord blood transplantation

BACKGROUND

Effect of single or multiple mismatches at each HLA locus on outcomes after cord blood transplantation (CBT) is controversial.

OBJECTIVE

We analyzed the effects of single or multiple HLA-locus mismatches on the outcomes after single CBT using a Japanese registry data from the Japan Society for Hematopoietic Cell Transplantation (JSHCT).

STUDY DESIGN

Patients with acute leukemia and myelodysplastic syndromes, aged 16 years or older, who underwent their first CBT between 2003 and 2017 (n = 4,074) were included. The effect of the number of HLA-locus mismatches (0, 1, and 2, for the HLA-A, -B, -C, and -DRB1 loci) on outcomes was analyzed after adjusting for other significant variables.

RESULTS

The median age of the patients was 54 years. Median total nucleated and CD34 cell doses were 2.6 × 10⁷/kg and 0.8 × 10⁵/kg, respectively. The number of CBTs with single or double mismatches were 2,099 and 292 for HLA-A locus, 2,699 and 341 for HLA-B locus, 2,555 and 609 for HLA-C locus, and 2,593 and 571 for HLA-DRB1 locus, respectively. Single and double HLA-DRB1 mismatches were associated with a higher risk of grade II-IV acute graft-versus-host disease (GVHD, single: HR 1.29, P<0.001, double: HR 1.49, P<0.001, trend-P: P<0.001). Single and double mismatches at HLA-DRB1 as well as single mismatches at HLA-A and HLA-B were also associated with grade III-IV acute GVHD. Single and double HLA-B mismatches and double HLA-DRB1 mismatches were associated with a high risk of non-relapse mortality. On the other hand, double mismatches at HLA-A or HLA-DRB1 and single mismatches at HLA-B were associated with a lower risk of relapse.

CONCLUSION

HLA-DRB1 double mismatch was associated with high risks of grade II-IV and III-IV acute GVHD and non-relapse mortality but lower risk of relapse. Not only the locus mismatch but also the number of mismatches may be considered in cord blood unit selection.

The impact of GVHD on outcomes after adult single cord blood transplantation in European and Japanese populations

The impact of GVHD and graft-versus-leukemia effect in unrelated cord blood transplantation (UCBT) is controversial. In the Eurocord/ALWP EBMT and JSTCT/JDCHCT collaborative study, we evaluated the impact of GVHD on UCBT outcomes in Japanese and European registries. A total of 3,690 adult patients with acute leukemia who received their first single UCBT were included. A multivariate analysis of overall survival (OS) revealed a positive impact of grade II acute GVHD compared with grade 0-I GVHD, in the Japanese cohort (hazard ratio (HR), 0.81; P = 0.001), and an adverse impact in the European cohort (HR, 1.37; P = 0.007). A negative impact of grade III-IV acute GVHD on OS was observed regardless of registries. In the analysis of relapse, a positive impact of grade II acutes GVHD compared with grade 0-I GVHD was observed only in the Japanese cohort, regardless of disease risk. The positive impact of limited chronic GVHD on OS was observed only in the Japanese cohort. In conclusion, a positive impact of mild GVHD after a single UCBT was observed only in the Japanese cohort. This could explain the ethnic difference in UCBT outcomes and might contribute to the preference usage of UCBT in Japan.

A successful booster umbilical cord blood transplantation for a 10-year-old patient with beta-thalassemia major in India

Beta-thalassemia major is characterized by a genetic deficiency in synthesis of beta-globin chains, resulting in reduced levels of functional hemoglobin. It is characterized by anemia, hepatosplenomegaly, and iron overload due to repeated blood transfusion. Hematopoietic stem cell transplantation is currently the only known curative treatment. We present a case of a 10-year-old girl with beta-thalassemia major who was successfully cured with allogeneic booster umbilical cord blood (UCB) transplantation with outcome data after 3 years of transplantation, in India. Postdiagnosis, she was on regular once-a-month blood transfusion until the age of 10 years, with no improvement. No serious adverse events occurred in the patient post-UCB transplantation. Chronic graft versus host disease was limited and was managed by medicines. Signs of primary graft rejection were also not seen.

Cord blood index predicts engraftment and early non-relapse mortality in adult patients with single-unit cord blood transplantation

How to select optimal cord blood (CB) remains an important clinical question. We developed and validated an index of CB engraftment, the cord blood index (CBI), which uses three weighted variables representing cell doses and HLA mismatches. We modeled the neutrophil engraftment time with competing events by random survival forests for competing risks as a function of the predictors: total nucleated cells, CD34, colony-forming units for granulocytes/macrophages, and the number of HLA mismatches at the antigen and allele levels. The CBI defined three groups that had different neutrophil engraftment rates at day 30 (High, 83.7% [95% CI, 79.2-88.1%]; Intermediate, 77.0% [95% CI, 73.7-80.2%]; Low, 68.4% [95% CI, 63.6-73.2%]), platelet engraftment rates at day 60 (High, 70.4% [95% CI, 64.9-75.9%]; Intermediate, 62.3% [95% CI, 58.5-66.0%]; Low, 49.3% [95% CI, 44.2-54.5%]), and non-relapse mortality at day 100 (High, 14.1% [95% CI, 9.9-18.3%]; Intermediate, 16.4% [95% CI, 13.5-19.3%]; Low, 21.3% [95% CI, 17.1-25.5%]). This novel approach is clinically beneficial and can be adopted immediately because it uses easily obtained pre-freeze data of CB.

Prognostic impact of the dosage of methotrexate combined with tacrolimus for graft-versus-host disease prophylaxis after cord blood transplantation

The optimal dosage of methotrexate (MTX) for graft-versus-host disease (GVHD) prophylaxis after cord blood transplantation (CBT) has not been well elucidated. Therefore, we conducted a retrospective study comparing a mini-MTX group (5 mg/m² on day 1, 3 and 6) to a short-MTX group (10 mg/m² on day 1 and 7 mg/m² on day 3 and 6) after CBT. Sixty-three patients were classified as the mini-MTX group and 20 as the short-MTX group. The median time and cumulative incidence of neutrophil engraftment did not vary between the two groups. The cumulative incidence of grade 2-4 and grade 3-4 acute GVHD was similar in both groups. Overall survival in the mini-MTX group was significantly lower than in the short-MTX group (46.9% vs. 88.7% at 1 year, p < 0.01), contributing to higher non-relapse mortality (NRM) in the mini-MTX group (32.0% vs. 5.0% at 1 year, p = 0.02). In multivariate analysis, the mini-MTX regimen was the most powerful prognostic factor for OS (hazard ratio 4.11; p = 0.03). Although the reduced dosage of MTX had no effect on neutrophil engraftment, increased NRM due to higher incidence of infection, graft failure, and severe acute GVHD resulted in a lower survival rate in the mini-MTX group after CBT.

High Integrity and Fidelity of Long-Term Cryopreserved Umbilical Cord Blood for Transplantation

Umbilical cord blood (UCB) is used as a source of donor cells for hematopoietic stem cell (HSC) transplantation. The success of transplantation is dependent on the quality of cord blood (CB) units for maximizing the chance of engraftment. Improved outcomes following transplantation are associated with certain factors of cryopreserved CB units: total volume and total nucleated cell (TNC) count, mononuclear cell (MNC) count, and CD34+ cell count. The role of the storage period of CB units in determining the viability and counts of cells is less clear and is related to the quality of cryopreserved CB units. Herein, we demonstrate the recovery of viable TNCs and CD34+ cells, as well as the MNC viability in 20-year-old cryopreserved CB units in a CB bank (MEDIPOST Co., Ltd., Seongnam-si, Gyeonggi-do, Korea). In addition, cell populations in CB units were evaluated for future clinical applications. The stable recovery rate of the viability of cryopreserved CB that had been stored for up to 20 years suggested the possibility of uses of the long-term cryopreservation of CB units. Similar relationships were observed in the recovery of TNCs and CD34+ cells in units of cryopreserved and fresh CB. The high-viability recovery of long-term cryopreserved CB suggests that successful hematopoietic stem cell (HSC) transplantation and other clinical applications, which are suitable for treating incurable diseases, may be performed regardless of long-term storage.

Impact of T Cell Repertoire Diversity on Mortality Following Cord Blood Transplantation

Introduction

Cord blood transplantation (CBT) recipients are at increased risk of mortality due to delayed immune recovery (IR). Prior studies in CBT patients have shown that recovery of absolute lymphocyte count is predictive of survival after transplant. However, there are no data on the association of T-cell receptor (TCR) and clinical outcomes after CBT. Here we retrospectively performed TCR beta chain sequencing on peripheral blood (PB) samples of 34 CBT patients.

Methods

All patients received a total body irradiation based conditioning regimen and cyclosporine and MMF were used for graft versus host disease (GvHD) prophylaxis. PB was collected pretransplant on days 28, 56, 80, 180, and 1-year posttransplant for retrospective analysis of IR utilizing high-throughput sequencing of TCRβ rearrangements from genomic DNA extracted from PB mononuclear cells. To test the association between TCR repertoire diversity and patient outcomes, we conducted a permutation test on median TCR repertoire diversity for patients who died within the first year posttransplant versus those who survived.

Results

Median age was 27 (range 1–58 years) and most of the patients (n = 27) had acute leukemias. There were 15 deaths occurring between 34 to 335 days after transplant. Seven deaths were due to relapse. Rapid turnover of T cell clones was observed at each time point, with TCR repertoires stabilizing by 1-year posttransplant. TCR diversity values at day 100 for patients who died between 100 and 365 days posttransplant were significantly lower than those of the surviving patients (p = 0.01).

Conclusions

Using a fast high-throughput TCR sequencing assay we have demonstrated that high TCR diversity is associated with better patient outcomes following CBT. Importantly, this assay is easily performed on posttransplant PB samples, even as early as day 28 posttransplant, making it an excellent candidate for early identification of patients at high risk of death.

Guidelines for Cord Blood Unit Selection

Optimal cord blood (CB) unit selection is critical to maximize the likelihood of successful engraftment and survival after CB transplantation (CBT). However, unit selection can be complex because multiple characteristics must be considered including unit cell dose, donor-recipient human leukocyte antigen (HLA) match, and unit quality. This review provides evidence-based and experience-based comprehensive guidelines for CB unit selection. Topics addressed include the use of both the TNC and the CD34⁺ cell dose, as well as the CD34⁺ cell to TNC content ratio to evaluate unit progenitor cell content and engraftment potential, the acceptable TNC and CD34⁺ cell dose criteria that define an adequate single-unit graft, and the indication and acceptable cell dose criteria for double-unit grafts. The acceptable criteria for 6-loci (HLA-A, -B antigen, -DRB1 allele) and 8-allele (HLA-A, -B, -C, -DRB1) donor-recipient HLA match, the evaluation of patients with donor-specific HLA antibodies, and the multiple determinants of unit quality are also reviewed in detail. Finally, a practical step-by-step guide to CB searches and the principles that guide ultimate graft selection are outlined.

Cord blood transplantation for acute leukemia

INTRODUCTION

Umbilical cord blood transplantation (UCBT) is a suitable alternative for patients with acute leukemia (AL) in need of an allograft and who lack an HLA-matched donor. Single-institution and registry studies have shown that, in both children and adults with AL, the outcome of UCBT is comparable to that of matched unrelated donor. At the same time, these studies have highlighted some limitations of UCBT, such as increased early mortality and delayed recovery of both hematopoietic and immune compartment, which hamper a more widespread adoption of this approach.

AREAS COVERED

In this review, we will analyze the current results of UCBT in children and adults with AL, including comparisons with other hematopoietic stem cell sources and transplant strategies. We will also discuss important factors to be considered when selecting UCB units, as well as future strategies to further improve the outcome of UCBT recipients.

EXPERT OPINION

The utilization of UCBT for the treatment of AL patients has decreased in recent years. However, recent clinical data suggesting that UCBT might offer better results in patients with minimal residual disease, as well as innovative strategies to facilitate engraftment, reduce transplant-related mortality, and optimize anti-leukemic activity, may pave the way toward a second youth for use of UCB cells.

Effect of graft-versus-host disease on outcomes after pediatric single cord blood transplantation

The effect of GVHD on transplant outcomes after unrelated cord blood transplantation (UCBT) is not yet fully understood. Pediatric patients aged 0-15 years with acute leukemia or myelodysplastic syndrome who underwent their first UCBT (n = 740) were selected from the Japanese registry. Fifty percent of the patients received a UCB unit containing more than 5.0 × 10⁷/kg total nucleated cells. The occurrence of grade III-IV acute GVHD was associated with a higher risk of non-relapse mortality (NRM, hazard ratio [HR] 4.07, P < 0.001) compared with no acute GVHD. Grade I-II acute GVHD was not associated with NRM. The occurrence of grade I-II or grade III-IV acute GVHD was not associated with a relapse risk. These findings showed that grade I-II acute GVHD carried no survival benefit and grade III-IV acute GVHD had an adverse effect (HR 1.68, P = 0.007). The occurrence of limited chronic GVHD was associated with a low risk of overall mortality (HR 0.60, P = 0.045). Severe acute GVHD should be prevented because of its association with high overall mortality and NRM in pediatric single UCBT. Mild acute GVHD provides no overall benefit. Mild chronic GVHD may be beneficial for survival.

Effects of Haplotype Matching on Outcomes after Adult Single-Cord Blood Transplantation

It remains unclear whether the HLA haplotype of unrelated cord blood (UCB) should be matched to that of the patient in single UCB transplantation. Thus, using data from a Japanese registry, we analyzed the effect of haplotype matching on outcomes. Patients with hematologic diseases aged 16 years or older who had undergone their first transplant were included (N = 1347). The effects of haplotype matching and high-frequency HLA haplotype on outcomes were analyzed. Median patient age was 55 years. The cumulative incidences of neutrophil engraftment among groups with 0, 1, and 2 HLA haplotype matches were 79%, 82%, and 88%, respectively (P = .008). In a multivariate analysis, the group with 0 haplotype matches was marginally associated with worse neutrophil engraftment (P = .087) and significantly associated with platelet engraftment (P = .044) compared with the group with 1 haplotype match. Two-haplotype matches were associated with a higher risk of relapse. In the group with 1 haplotype match, the top 3 shared haplotypes were "A*24:02-B*52:01-C*12:02-DRB1*15:02" (HP-P1), "A*33:03-B*44:03-C*14:03-DRB1*13:02" (HP-P2), and "A*24:02-B*07:02-C*07:02-DRB1*01:01" (HP-P3). The presence of HP-P2 but not HP-P1 or HP-P3 was associated with a decreased risk of grades II to IV acute graft-versus-host disease (hazard ratio, .56; P = .001) but an increased risk of relapse (hazard ratio, 1.35; P = .045). HLA haplotype matching might be considered to improve engraftment. Two-haplotype matches should be avoided if the relapse risk is high. The haplotype itself may have an effect on the risk of acute graft-versus-host disease and relapse.

Stem cell banking: Are South Indian mothers aware?

Umbilical cord blood (UCB) is an important source of stem cells, the heart of regenerative medicine. As the globalization and population of the world continues to increase, we are faced with an inundation of new diseases, affecting millions of people. Research work considering stem cells is essential for developing therapy for various conditions. Reduced availability of UCB serves as a hindrance to promote further research. Hence, India being one of the most densely populated countries in the world, can be considered a potential UCB repository. In this study 428 mothers of children born in the period from 2012 to 2017 were asked to fill questionnaires that evaluated their awareness regarding stem cell banking. This investigation deliberates if expectant mothers in this region are aware of stem cell banking and if there is a significant pattern regarding awareness based on parameters like age, educational qualification, locality, annual income and consulted hospitals. Although, majority of the women were unaware of this facility, knowledge was heightened in wealthy, educated, women from urban areas who consulted private hospitals. Hence, great efforts need to be made to further the awareness of expectant mothers in South India regarding UCB storage and donation.

Cohort-Controlled Comparison of Umbilical Cord Blood Transplantation Using Carlecortemcel-L, a Single Progenitor-Enriched Cord Blood, to Double Cord Blood Unit Transplantation

Umbilical cord blood (UCB) transplantation has a high early mortality rate primarily related to transplanted stem cell dose. To decrease early mortality and enhance engraftment, a portion of selected cord blood units (20% to 50%) was expanded with cytokines and the copper chelator tetraethylenepentamine (carlecortemcel-L) and transplanted with the unmanipulated fraction after myeloablative conditioning. The primary endpoint was 100-day survival, which was compared with a contemporaneous double-unit cord blood transplantation (DUCBT) group. We enrolled 101 patients at 25 sites; the DUCBT comparison (n = 295) was selected from international registries using study eligibility criteria. Baseline carlecortemcel-L study group unit nucleated cell (NC) and CD34⁺ were 3.06 × 10⁷ cell dose/kg and 1.64 × 10⁵ cell dose/kg. Median NC and CD34⁺ fold expansion were 400 and 77, with a mean total CD34 infused of 9.7 × 10⁵/kg. The 100-day survival was 84.2% for the carlecortemcel-L study group versus 74.6% for the DUCBT group (odds ratio, .50; 95% CI, .26 to .95; P = .035). Survival at day 180 was similar for the 2 groups; the major cause of death after day 100 was opportunistic infections. Faster median neutrophil (21 days versus 28 days; P < .0001), and platelet (54 days versus 105 days; P = .008) engraftment was seen in the carlecortemcel-L study group; acute and chronic graft-versus-host disease rates were similar. In this multinational comparative study, transplanting expanded CD34⁺ stem cells from a portion of a single UCB unit, with the remaining unmanipulated fraction improved 100-day survival compared with DUCBT control patients while facilitating myeloid and platelet engraftment. This trial was registered at www.clinicaltrials.gov as #NCT00469729.

An Integrative Scoring System for Survival Prediction Following Umbilical Cord Blood Transplantation in Acute Leukemia

Purpose: Survival of acute leukemia (AL) patients following umbilical cord blood transplantation (UCBT) is dependent on an array of individual features. Integrative models for risk assessment are lacking. We sought to develop a scoring system for prediction of overall survival (OS) and leukemia-free survival (LFS) at 2 years following UCBT in AL patients.Experimental Design: The study cohort included 3,140 pediatric and adult AL UCBT patients from the European Society of Blood and Marrow Transplantation and Eurocord registries. Patients received single or double cord blood units. The dataset was geographically split into a derivation (n = 2,362, 65%) and validation set (n = 778, 35%). Top predictors of OS were identified using the Random Survival Forest algorithm and introduced into a Cox regression model, which served for the construction of the UCBT risk score.Results: The score includes nine variables: disease status, diagnosis, cell dose, age, center experience, cytomegalovirus serostatus, degree of HLA mismatch, previous autograft, and anti-thymocyte globulin administration. Over the validation set an increasing score was associated with decreasing probabilities for 2 years OS and LFS, ranging from 70.21% [68.89-70.71, 95% confidence interval (CI)] and 64.76% (64.33-65.86, 95% CI) to 14.78% (10.91-17.41) and 18.11% (14.40-22.30), respectively. It stratified patients into six distinct risk groups. The score's discrimination (AUC) over multiple imputations of the validation set was 68.76 (68.19-69.04, range) and 65.78 (65.20-66.28) for 2 years OS and LFS, respectively.Conclusions: The UCBT score is a simple tool for risk stratification of AL patients undergoing UCBT. Widespread application of the score will require further independent validation. Clin Cancer Res; 23(21); 6478-86. ©2017 AACR.

From patient centered risk factors to comprehensive prognostic models: a suggested framework for outcome prediction in umbilical cord blood transplantation

Prospectively identifying patients who will gain maximal benefit from umbilical cord blood transplantation (UCBT) with minimal risk is a desirable unmet need. A complex network of parameters related to patient, disease, donor, and procedure all come into play. We review the prognostic role of patient-related risk factors in adults undergoing UCBT. Furthermore, since comprehensive prognostic models are lacking in UCBT, we suggest a framework for integrating patients' features in the development of prediction models for UCBT outcomes. Such models could contribute to patient selection, optimization of the various modifiable features in the process of UCBT, analysis of retrospective data, and design of interventions.

Use of allogeneic apheresis stem cell products as an interlaboratory proficiency challenge

BACKGROUND

AABB Standards requires that laboratories participate in a proficiency test (PT) program for critical analytes. Institutions can purchase commercial PT materials; however, PT can also be performed through interlaboratory exchange. We investigated the utility of allogeneic hematopoietic progenitor cell apheresis (HPC-A) products as an interlaboratory PT challenge for total nucleated cell count (TNC) and CD34 assessment.

STUDY DESIGN AND METHODS

Three-year retrospective and comparative review of unrelated allogeneic HPC-A products received by the University of Michigan between January 2011 and December 2013. Internal TNC and CD34 count were compared to the external collecting facility by paired t test and linear regression. The absolute and percent difference between external and internal counts and 95% limits of agreeability (95% LA) were determined. Results were analyzed relative to donor center location (international, domestic), time zone (domestic), and calendar year.

RESULTS

There was a strong correlation between internal and external TNC, regardless of donor center location or year. For CD34, there was a good correlation between centers (R = 0.88-0.91; slope = 0.95-0.98x) with a median difference of -1% (95% LA, -50%, +47%). This was considerably better than commercial PT challenges, which showed a persistent negative bias for absolute CD34 and CD3 counts.

CONCLUSION

Allogeneic HPC-A products represent an interlaboratory PT exchange for all critical analytes, including TNC and CD34 count, cell viability, and sterility. Allogeneic HPC-A products, which are fresh and transported under validated conditions, are less subject to preanalytical variables that may impact commercial PT samples such as aliquoting and sample homogeneity, commercial additives, and sample stability during manufacturing and transport.

Impact of graft-versus-host disease on outcomes after unrelated cord blood transplantation

The effect of graft-versus-host disease (GVHD) on transplant outcomes after unrelated cord blood transplantation (UCBT) has not been fully elucidated. We analyzed the impact of acute and chronic GVHD on outcomes in adult patients with acute leukemia or myelodysplastic syndrome who underwent their first UCBT (n=2558). The effect of GVHD on outcomes was analyzed after adjusting for other significant variables. The occurrence of GVHD was treated as a time-dependent covariate. The occurrence of grade 1-2 or 3-4 acute GVHD was significantly associated with a lower relapse rate. Grade 3-4 acute GVHD was associated with a higher risk of non-relapse and overall mortality than no acute GVHD, whereas grade 1-2 acute GVHD was associated with a lower risk of non-relapse and overall mortality than no acute GVHD. Limited or extensive chronic GVHD was significantly associated with a lower relapse rate. Limited chronic GVHD was associated with a lower overall and non-relapse mortality than no chronic GVHD. In conclusion, mild acute or chronic GVHD was associated not only with a low risk of relapse but also with a low risk of non-relapse mortality, and provides a survival benefit in UCBT.

Impact of Donor and Recipient Cytomegalovirus Serostatus on Outcomes of Antithymocyte Globulin-Conditioned Hematopoietic Cell Transplantation

Although previous studies involving allogeneic hematopoietic cell transplantation (HCT) without in vivo T cell depletion by rabbit antithymocyte globulin (ATG) have reported a substantial survival difference between D-R- and D+R- patients, but little to no survival difference between D-R+ and D+R+ patients (D, donor; R, recipient; +, cytomegalovirus [CMV] seropositive; -, CMV seronegative), whether this applies to HCT using ATG is unknown. We studied 928 patients who underwent myeloablative HCT for hematologic malignancies in Alberta between 1999 and 2014 who received graft-versus-host disease (GVHD) prophylaxis using ATG (Thymoglobulin, 4.5 mg/kg) in addition to methotrexate and cyclosporine. D-R- and D+R- patients had similar survival (no significant difference). D-R+ patients had a substantially lower survival than D+R+ patients (41% versus 59% at 5 years; P = .001). This difference was attributed to higher nonrelapse mortality, apparently due to higher GVHD-associated mortality. Survival rates were also lower for D-R+ HLA-matched sibling transplant recipients compared with D+R+ HLA-matched unrelated donor transplant recipients (44% versus 66% at 5 years; P = .009). In conclusion, when using ATG, choosing a seronegative donor for a seronegative patient is relatively unimportant, whereas choosing a seropositive donor for a seropositive patient is important, even if this requires the use of a seropositive matched unrelated donor graft.

Methods of ex vivo expansion of human cord blood cells: challenges, successes and clinical implications

More than 40,000 unrelated cord blood transplantations (UCBT) have been performed worldwide as treatment for patients with malignant or non-malignant life threatening hematologic disorders. However, low absolute numbers of hematopoietic stem and progenitor cells (HSPCs) within a single cord blood unit has remained a limiting factor for this transplantation modality, particularly in adult recipients. Further, because UCB contains low numbers of mostly naïve T cells, immune recovery after UCBT is slow, predisposing patients to severe infections. Other causes of UCBT failure has included graft-versus-host disease (GVHD) and relapse of the underlying disease. In this article, we first review the current landscape of cord blood engineering aimed at improving engraftment. This includes approaches of UCB-HSPCs expansion and methods aimed at improving UCB-HSCPs homing. We then discuss recent approaches of cord blood engineering developed to prevent infection [generation of multivirus-specific cytotoxic T cells (VSTs) from UCB], relapse [transduction of UCB-T cells with tumor-specific chimeric receptor antigens (CARs)] and GVHD (expansion of regulatory T cells from UCB). Although many of these techniques of UCB engineering remain currently technically challenging and expensive, they are likely to revolutionize the field of UCBT in the next decades.

Alternative donors: cord blood for adults

Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for patients with hematological diseases. The probability of finding a human leukocyte antigen (HLA)- identical donor among family members is around 25% and 30% that of having a full matched unrelated donor in the registry. Patients in need may also benefit of a HLA-mismatched HSCT either from an haploidentical donors or from umbilical cord blood (UCB). Much has been learned about UCB transplant (UCBT) since the first human UCBT was performed back in 1988. Cord blood banks have been established worldwide for the collection, cryopreservation, and distribution of UCB for HSCT. Today, a global network of cord blood banks and transplant centers has been established with a large common inventory of more than 650,000 UCB units available, allowing for more than 40,000 UCBT worldwide in children and adults with severe hematological diseases. Several studies have been published on UCBT, assessing risk factors such as cell dose and HLA mismatch. Outcomes of several retrospective comparative studies showed similar results using other stem cell sources both in pediatric and adult setting. New strategies are ongoing to facilitate engraftment and reduce transplant-related mortality. In this issue, we review the current results of UCBT in adults with hematological malignancies and the clinical studies comparing UCBT with other transplant strategies. We provide guidelines for donor algorithm selection in UCBT setting.

Cord blood transplant for acute myeloid leukaemia

Umbilical cord blood is a haematopoietic progenitor cell source for patients with acute myeloid leukaemia (AML), other haematological malignancies and metabolic diseases who can be cured by allogeneic haematopoietic cell transplantation, but who do not have a human leucocyte antigen compatible related or unrelated donor. Although the first cord blood transplants were done in children, there are currently more cord blood transplants performed in adults. In this review, we explore the history of umbilical cord blood transplantation, paediatric and adult outcome results, and novel trends to improve engraftment and reduce infection. Umbilical cord blood transplantation cures approximately 30-40% of adults and 60-70% of children with AML. Controversial issues, including the use of double versus single cord blood units for transplantation, optimal cord blood unit selection, infection prophylaxis, conditioning regimens and graft versus host disease prophylaxis, will be reviewed. Finally, comparison to other graft sources, cost, access to care, and the ideal graft source are discussed.

Severe infections after single umbilical cord blood transplantation in adults with or without the co-infusion of CD34+ cells from a third-party donor: results of a multicenter study from the Grupo Español de Trasplante Hematopoyético (GETH)

BACKGROUND

Umbilical cord blood transplantation (CBT) is an established alternative source of stem cells in the setting of unrelated transplantation. When compared with other sources, single-unit CBT (sCBT) is associated with a delayed hematologic recovery, which may lead to a higher infection-related mortality (IRM). Co-infusion with the sCBT of CD34+ peripheral blood stem cells from a third-party donor (TPD) (sCBT + TPDCD34+) has been shown to markedly accelerate leukocyte recovery, potentially reducing the IRM. However, to our knowledge, no comparative studies have focused on severe infections and IRM with these 2 sCBT strategies.

METHODS

A total of 148 consecutive sCBT (2000-2010, median follow-up 4.5 years) were included in a multicenter retrospective study to analyze the incidence and risk factors of IRM and severe viral and invasive fungal infections (IFIs). Neutrophil engraftment occurred in 90% of sCBT (n = 77) and 94% sCBT + TPDCD34+ (n = 71) recipients at a median of 23 and 12 days post transplantation, respectively (P < 0.01).

RESULTS

The 4-year IRM was 24% and 20%, respectively (P = 0.7), with no differences at day +30 (5% and 4%, respectively) and day +100 (10% and 8%, respectively). In multivariate analysis early status of the underlying malignancy, cytomegalovirus (CMV)-seronegative recipient and high CD34+ cell content in the cord blood unit before cryostorage (≥1.4 × 10(5) /kg) were protective of IRM. Among the causes of IRM, bacterial infections and IFIs were more common in sCBT (15% vs. 4%), while CMV disease and parasitic infections were more common in the sCBT + TPDCD34+ cohort (5% vs. 16%).

CONCLUSION

These data show that sCBT supported with TPDCD34(+) cells results in much shorter periods of post-transplant leukopenia, but the short- and long-term rates of IRM were comparable to those of sCBT, presumably because immune recovery is equally delayed in both graft types.

Efficiency of high-dose cytarabine added to CY/TBI in cord blood transplantation for myeloid malignancy

Cord blood transplantation (CBT) is an effective therapeutic option for adults with acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS) after the conventional cyclophosphamide and total body irradiation (CY/TBI) regimen, but posttransplant relapse is still of high importance. High-dose cytarabine (HDCA) can be added to CY/TBI for an intensified regimen; however, its additional effects have not yet been completely elucidated. Therefore, we conducted a cohort study to compare the prognosis of HDCA/CY/TBI (n = 617) and CY/TBI (n = 312) in CBT for AML/MDS, using a Japanese transplant registry database. The median age was 40 years, and 86.2% of the patients had AML; high-risk disease was observed in 56.2% of the patients. The median follow-up period after CBT was approximately 3.5 years. Overall survival was significantly superior in the HDCA/CY/TBI group (adjusted hazard ratio [HR], 0.56; 95% confidence interval [CI], 0.45-0.69; P < .01), and tumor-related mortality was lower (HR, 0.50; P < .01). The incidence of grade II to IV acute graft-vs-host disease (aGVHD) and chronic GVHD was significantly higher in the HDCA/CY/TBI group (HR, 1.33 and 2.30, respectively), but not grade III to IV aGVHD. Incidence of infectious episodes showed no significant difference. Nonrelapse mortality was not increased by the addition of HDCA. Higher-dose CA (12 rather than 8 g/m(2)) was more effective, particularly in patients at high-risk for disease. This study is the first to show the superiority of HDCA/CY/TBI to CY/TBI in CBT for AML/MDS. A large-scale prospective study is warranted to establish new conditioning regimens including HDCA administration.

Optimal method for collection of umbilical cord blood: an Egyptian trial for a public cord blood bank

BACKGROUND

Umbilical cord blood (UCB) contains stem cells and can be used as an alternative to bone marrow transplantation. Engraftment is dependent on the total nucleated cell (TNC) and CD34+ cell counts of the cord blood units. This study was designed to evaluate the effect of the method of collection of the UCB on the yield of the cord blood units.

STUDY DESIGN AND METHODS

Informed consent was obtained from 100 eligible mothers for donation of cord blood. Both in utero and ex utero methods were used for collection. The cord blood volume was measured. The TNC and the CD34+ cell counts were enumerated.

RESULTS

We have found that in utero collection gave significantly larger volumes of cord blood and higher TNC counts than ex utero collection. There was no significant difference between both methods regarding the CD34+ cell counts. This study revealed a significant correlation between the volume of the collected cord blood and both TNC and CD34+ cell counts.

CONCLUSION

It is better to collect cord blood in utero before placental delivery to optimize the quality of the cord blood unit.

Combined umbilical cord blood and bone marrow from HLA-identical sibling donors for hematopoietic stem cell transplantation in children with hemoglobinopathies

BACKGROUND

It is well established that umbilical cord blood and bone marrow are biologically different stem cell sources.

PATIENTS AND METHODS

We analyzed the feasibility and outcome of hematopoietic stem cell transplantation (HSCT) in 13 children (median age 5.9 years) with hemoglobinopathies after the co- infusion of cord blood (CB) and bone marrow (BM) from the same human leucocyte antigen (HLA) identical sibling donor. We also compared outcomes of children with co-transplantation to outcomes in children with hemoglobinopathies who had received a BM (n = 21) or CB (n = 22) transplant alone.

RESULTS

Compared to CB transplant (CBT) recipients, the co-transplant group had more rapid neutrophil (17 vs. 25 days, P = 0.013) and platelet (29 vs. 48 days, P = 0.009) recovery and less transplant related mortality. Patients who received a co-transplant had a lower incidence of ≥ grade II acute (0% vs. 26.3%) and chronic (0% vs. 21%) graft versus host disease (GVHD) compared to BM transplant (BMT) recipients (P = 0.055 and 0.045, respectively). With a median follow-up of >60 months in each treatment group, the 5-year probability of event free survival (EFS) was 100% in the co-transplant group, 90% after BMT and 86% after CBT (P = 0.42).

CONCLUSION

Co-transplantation of CB and BM from HLA-identical sibling donors appears to be a feasible and effective strategy to further optimize outcomes of HSCT for hemoglobinopathies.

Hematopoietic stem cell transplantation donor sources in the 21st century: choosing the ideal donor when a perfect match does not exist

Most patients who require allogeneic stem cell transplantation do not have a matched sibling donor, and many patients do not have a matched unrelated donor. In an effort to increase the applicability of transplantation, alternative donors such as mismatched adult unrelated donors, haploidentical related donors, and umbilical cord blood stem cell products are frequently used when a well matched donor is unavailable. We do not yet have the benefit of randomized trials comparing alternative donor stem cell sources to inform the choice of donor; however, the existing data allow some inferences to be made on the basis of existing observational and phase 2 studies. All 3 alternative donor sources can provide effective lymphohematopoietic reconstitution, but time to engraftment, graft failure rate, graft-versus-host disease, transplant-related mortality, and relapse risk vary by donor source. These factors all contribute to survival outcomes and an understanding of them should help guide clinicians when choosing among alternative donor sources when a matched related or matched unrelated donor is not available.

Effect of CD8⁺ cell content on umbilical cord blood transplantation in adults with hematological malignancies

Total nucleated (TNCs) and CD34(+) cells are considered major determinants of outcome after umbilical cord blood (UCB) transplantation but the effect of other cell subtypes present in the graft is unknown. This single-center cohort study included patients with hematological malignancies who received UCB transplantation after a myeloablative conditioning regimen. UCB units were primarily selected according to cell content, both TNCs and CD34(+) cells, and also according to the degree of HLA matching. Counts of several cell subtypes of the infused UCB unit, together with HLA disparities and other patient- and transplantation-related characteristics, were analyzed by multivariable methodology for their association with myeloid and platelet engraftment, graft-versus-host disease, nonrelapse mortality (NRM), disease-free survival (DFS), and overall survival (OS). Two hundred patients (median age, 32 years) were included in the study. In multivariable analyses, a greater number of CD8(+) cells was significantly associated with better results for myeloid (P = .001) and platelet (P = .008) engraftment, NRM (P = .02), DFS (P = .007), and OS (P = .01). CD34(+) cell content was predictive of myeloid engraftment (P < .001). This study suggests that the outcome after UCB transplantation in adults with hematological malignancies could be better when UCB grafts had a greater CD8(+) cell content.

Cord blood banking and transplantation: advances and controversies

PURPOSE OF REVIEW

A review of articles published since January 2012 on the topic of cord blood banking and cord blood stem cell transplantation was conducted for this the 25th anniversary year of the first cord blood transplant performed in a human.

RECENT FINDINGS

Cord blood banking is performed throughout the world. Umbilical cord blood (UCB) transplantation is recognized as an acceptable alternative stem cell source for paediatric and adults requiring a haematopoietic transplant, particularly for patients of racial and ethnic minorities. To further advance the use of UCB, methods to enhance UCB stem cell expansion, engraftment and maintenance may be required. Controversy on the most effective and economically sustainable model for banking and storing an optimal UCB product continues to persist.

SUMMARY

Cord blood banking and transplantation of cord blood stem cells has advanced rapidly over the initial 25 years, as more than 30 ,000 patients have benefited from the therapy. New concepts on the use of methods to expand UCB stem cells for transplantation and use for nonhaematopoietic indications may increase demand for UCB over the next few decades.

Myeloablative cord blood transplantation in adults with acute leukemia: comparison of two different transplant platforms

We compared the clinical outcomes of adults with acute leukemia that received single-unit umbilical cord blood transplantation (sUCBT) after conditioning with a busulfan/antithymocyte globulin (BU-ATG)-based regimen at University Hospital La Fe (n = 102) or double-unit UCBT (dUCBT) after conditioning with a total body irradiation (TBI)-based regimen at the University of Minnesota (n = 91). Nonrelapse mortality, relapse and disease-free survival were similar in the 2 groups. Multivariate analyses, showed more rapid neutrophil (hazard ratio [HR], .6; 95% confidence interval [CI], .45 to .80; P = .0006) and platelet recovery (HR, .59; 95% CI, .43 to.83; P = .002) after the BU-ATG-based conditioning and sUCBT. Although there was a lower risk of acute graft-versus-host disease (GVHD) grade II to IV (HR, 2.81; 95% CI, 1.75 to 4.35; P < .001) after BU-ATG and sUCBT, the incidences of grade III to IV acute and chronic GVHD were similar between the 2 groups. Regarding disease-specific outcomes, disease-free survival in both acute myeloid leukemia and acute lymphoblastic leukemia (ALL) patients were not significantly different; however, a significantly lower relapse rate was found in patients with ALL treated with TBI and dUCBT (HR, .3; 95% CI, .12 to .84; P = .02). In the context of these specific treatment platforms, our study demonstrates that sUCB and dUCBT offer similar outcomes.

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.

Different effects of HLA disparity on transplant outcomes after single-unit cord blood transplantation between pediatric and adult patients with leukemia

Recent advances in unrelated cord blood transplantation have increased chances and options available in allogeneic stem cell transplantation. The effect of HLA disparity on outcomes after cord blood transplantation was studied recently in mainly pediatric populations. Results showed that HLA matching in combination with total nucleated cell dose positively affects survival. The effect of HLA disparity after single-unit cord blood transplantation may be different in adults because their total nucleated cell dose is much lower compared to pediatric patients. We investigated the effect of HLA disparity on the outcome of single-unit unrelated cord blood transplantation separately in 498 children aged 15 years or under (HLA-A, HLA-B low-resolution, and HLA-DRB1 high-resolution matched [6/6], n=82, and one locus- [5/6], n=222, two loci- [4/6], n=158, three loci- [3/6] mismatched, n=36) and 1,880 adults (6/6, n=71; 5/6, n=309; 4/6, n=1,025; 3/6, n=475) with leukemia. With adjusted analyses, in children, 4/6 showed significantly increased risks of overall mortality (relative risk [RR]=1.61, P=0.042) and transplant-related mortality (RR=3.55, P=0.005) compared to 6/6. The risk of grade 2 to 4 acute GVHD was increased in 5/6 (RR=2.13, P=0.004) and 4/6 (RR=2.65, P<0.001). In adults, the risk of mortality did not increase with the number of mismatched loci (RR=0.99, P=0.944 for 5/6; RR=0.88, P=0.436 for 4/6). The risk of relapse was significantly decreased in 4/6 (RR=0.67, P=0.034). The risk of transplant-related mortality (TRM) or acute GVHD was not increased in 5/6 or 4/6. The effect of HLA disparity on transplant outcome differed between children and adults. In children, an increased number of mismatched HLA loci correlated with an increased risk of mortality. In adults, there was no increase in mortality with an increase in the number of mismatched HLA loci.

Can double-cord transplants provide a more potent graft-vs-leukemia effect?

When an HLA-identical sibling is unavailable in a patient who needs allogeneic transplant, physicians are faced with the choice of several alternative donor types: matched unrelated donors, mismatched unrelated donors, and single- or double-unit umbilical cord (UCB) blood grafts. UCB transplant is a viable alternative for many patients, though adolescents and adults are limited to double-unit grafts due to dose limitations. Double-unit UCB transplants after myeloablative conditioning regimens have been linked with lower relapse rates than other donor types, though they are also associated with longer time to hematopoietic engraftment and subsequent higher rates of non-relapse mortality. The role of double-unit UCB transplants in reducing relapse incidence is less clear with reduced-intensity conditioning regimens.