Role of HLA Matching in Single Umbilical Cord Blood Transplantation Outcomes

Mild Acute Graft-Versus-Host Disease Improves Outcomes After HLA-Haploidentical-Related Donor Transplantation Using Posttransplant Cyclophosphamide and Cord Blood Transplantation

Haploidentical-related donor transplantation using posttransplant cyclophosphamide (PTCy-haplo) and cord blood transplantation (CBT) are valid alternatives for patients with hematological malignancies when HLA-matched donor transplantation (MDT) is unavailable. However, the effects of graft-versus-host disease (GVHD) on outcomes after these transplants have not been fully elucidated. Therefore, we evaluated the effects of acute and chronic GVHD on transplant outcomes after PTCy-haplo transplants and compared them with CBT and MDT. We included a total of 914 adult patients with hematological malignancies in the Kyoto Stem Cell Transplantation Group registry who received PTCy-haplo (N = 120), CBT (N = 402), and MDT (N = 392), and achieved neutrophil engraftment. A multivariate analysis revealed that grade I-II acute GVHD improved of overall survival (OS) after PTCy-haplo [hazard ratio (HR) = 0.39, P = 0.018] and CBT (HR = 0.48, P < 0.001), but not after MDT (HR = 0.80, P = 0.267) compared with patients without acute GVHD. Grade I-II acute GVHD had a trend toward reducing the risk of nonrelapse mortality (NRM) after PTCy-haplo (HR = 0.13, P = 0.060) and this positive effect was significant after CBT (HR = 0.39, P = 0.003). A negative impact of grade III-IV acute GVHD on NRM was observed after CBT and MDT, but not after PTCy-haplo. Limited chronic GVHD had a positive impact on OS after CBT and MDT, but not after PTCy-haplo. In conclusion, mild acute GVHD improved outcomes after PTCy-haplo and CBT, and limited chronic GVHD improved outcomes after CBT and MDT. These data indicated that the effects of GVHD on transplant outcomes depended on transplant platforms.

UM171 Expansion of Cord Blood Improves Donor Availability and HLA Matching For All Patients, Including Minorities

Cord blood (CB) stem cell transplantation offers a greater tolerance to HLA mismatches compared to adult-derived stem cell transplants (i.e., bone marrow or peripheral blood stem cells). Indeed, 4/6 or 5/8 HLA-matched CB transplantations are regularly performed for patients lacking a matched unrelated donor. Unfortunately, most banked CB units contain a stem cell dose that is too small to treat adult patients, resulting in only 4% to 5% of available CB units offering an adequate cell dose for prompt engraftment for adult patients. Ex vivo stem cell expansion appears to be an attractive strategy to circumvent this cell dose issue, while also enabling the selection of better HLA-matched CB units. In this study, we retrospectively performed HLA matching simulations to assess how the minimal cell content requirements associated with UM171 CB expansion may improve usability of existing CB unit inventories and donor availability for patients of different races and ethnicities. We analyzed a dataset of 58,971 adults for whom a donor search was initiated through the National Marrow Donor Program Be The Match registry against 142,942 CB units from major U.S. public CB banks listed on the Be The Match registry. Our results show that by enabling selection of smaller CB units, UM171-expanded CB transplantation increases donor availability from 72% to 84% for all patients compared to single unmanipulated CB transplantation. Furthermore, the low cell dose criteria for UM171-expanded CB also increases donor availability compared to double CB transplantation, while enabling better HLA matching between donor and recipient. UM171 expanded CB appears particularly beneficial for racial and ethnic minority patients as CB availability increases from 53% to 78% for African Americans, from 66% to 85% for Hispanics, and from 68% to 84% for Asians and Pacific Islanders, compared to single unmanipulated CB transplantation. In addition, UM171 expansion dramatically improves usability of CB units currently in inventories, as only 4.3% and 0.6% of banked CBs have sufficient cell doses for a 70 kg and 100 kg patient, respectively. UM171 raises this proportion to 53.8% and 20.2%, respectively, making CB banks potentially more cost effective. In conclusion, UM171 expansion allows the use of smaller CB units while also improving access to transplantation for racial and ethnic minorities.

Single Cord Blood Transplantation Versus HLA-Haploidentical-related Donor Transplantation Using Posttransplant Cyclophosphamide in Patients With Hematological Malignancies

BACKGROUND

Unrelated cord blood (UCB) and haploidentical related donor transplantation using posttransplant cyclophosphamide (PTCy-haplo) have become alternative options to treat patients with hematological malignancies without a HLA-matched donor.

METHODS

We conducted a retrospective study using registry data from the Kyoto Stem Cell Transplantation Group for patients with hematological malignancies who received their first allogeneic hematopoietic cell transplantation using a single UCB unit (n = 460) or PTCy-haplo (N = 57) between 2013 and 2019.

RESULTS

We found that overall survival in the UCB group was comparable to that in the PTCy-haplo group (hazard ratio, 1.00; 95% confidence interval, 0.66-1.52), although neutrophil and platelet engraftment were significantly delayed. Nonrelapse mortality risk and the incidence of graft-versus-host disease in the UCB group were also comparable to those in the PTCy-haplo group. Although the relapse risk was similar between the UCB group and the PTCy-haplo group regardless of the disease risk, acute myeloid leukemia patients benefit from UCB transplant with a significantly lower relapse rate (hazard ratio, 0.38; 95% confidence interval, 0.18-0.76).

CONCLUSIONS

UCB transplant gives outcomes comparable to PTCy-haplo transplant, and both UCB and PTCy-haplo units are suitable as alternative donor sources for patients without an HLA-matched sibling or unrelated donor.

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.

HLA 1-3 antigen-mismatched related peripheral blood stem cells transplantation using low-dose antithymocyte globulin versus unrelated cord blood transplantation

Little information is available regarding whether unrelated cord blood transplantation (CBT) or an HLA 1-3 antigen-mismatched related donor peripheral blood stem-cell transplantation (PBSCT) using low-dose anti-thymocyte globulin (ATG) is superior as an alternative transplantation for patients who lack an HLA-matched sibling or unrelated donor. Therefore, we evaluated 7861 patients with hematologic malignancies (aged 0 to 70 years) who received either a CBT without ATG (CBT-no ATG, n = 7034) or an HLA 1-3 antigen-mismatched related donor PBSCT using low-dose ATG (PBSCT-ATG, n = 827). CBT-no ATG was associated with significantly better overall survival (OS) than the use of a PBSCT-ATG (hazard ratio [HR], 0.77; p < .001), although PBSCT-ATG patients with an HLA 1 antigen-mismatch showed OS comparable to that in the CBT-no ATG group. Neutrophil and platelet engraftment was significantly delayed, whereas the incidences of nonrelapse mortality, and severe graft-versus-host disease (GVHD) were significantly lower in the CBT-no ATG group. The incidences of relapse and chronic GVHD were comparable between these donors. In conclusion, CBT-no ATG may be a better alternative than HLA-mismatched related donor PBSCT using low-dose ATG. Notably, HLA 2-3 antigen mismatch-related transplantation with low-dose ATG had significant adverse effects on transplantation outcomes.

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.

Favorable Outcomes after Single Cord Blood Transplantation for Patients with High-Risk Hematologic Diseases: A Single-Institute Retrospective Analysis

The donor selection algorithm for cord blood (CB) with regards to matched related and unrelated donors has not been fully investigated. To assess the potential of CB transplantation (CBT) in patients with hematologic malignancies, especially for high-risk patients, we performed a single-institute retrospective analysis and compared the clinical outcomes of CBT with those of HLA-matched sibling and unrelated donor transplantation. We included 394 patients aged 16 years and older with hematologic diseases who received their first allogeneic hematopoietic cell transplantation between 1990 and 2018 at Kyoto University Hospital. These included 394 recipients of single unrelated cord blood units (UCB, n = 108), HLA-matched sibling donors (MSDs, n = 143), or HLA-matched unrelated donors (MUDs, n = 143). There was no significant difference in relapse-free survival (RFS) between UCB, MSD, and MUD recipients (P = .975). However, we found a significant interaction between transplant year and CBT outcomes (P = .010), with significantly better outcomes observed in the more recent years. Furthermore, we found that CBT showed better RFS than matched donor transplantation (hazard ratio [HR], 0.50; 95% confidence interval [CI], 0.30 to 0.84). This impact was more prominent in high-risk patients (HR, 0.35; 95% CI, 0.16 to 0.77), with lower relapse rates (HR, 0.25; 95% CI, 0.11 to 0.54), and comparable non-relapse mortality (NRM) compared to matched donor transplantation. Extensive chronic graft-versus-host disease was less frequently observed in CBT (HR, 0.58; 95% CI, 0.26 to 1.28). CBT associated with favorable outcomes, particularly in high-risk patients, with good RFS and low relapse rates without an increase in NRM in the single-institute study. Although the findings should be externally validated, CBT might serve as a reasonable donor choice, particularly in high-risk patients.