Unlicensed Umbilical Cord Blood Units Provide a Safe and Effective Graft Source for a Diverse Population: A Study of 2456 Umbilical Cord Blood Recipients

Impact of Race and Ethnicity on Outcomes After Umbilical Cord Blood Transplantation

BACKGROUND

Umbilical cord blood transplant (UCBT) improves access to transplant for patients lacking a fully matched donor. Previous Center for International Blood and Marrow Transplant Research (CIBMTR) showed that Black patients had a lower overall survival (OS) than White patients following single UCBT. The current study draws on a larger modern cohort and compares outcomes among White, Latinx, Black, and Asian patients.

OBJECTIVE

To compare outcomes by social determinants of health.

STUDY DESIGN

We designed a retrospective study using CIBMTR data. US patients were between ages 1 and 80; 983 received single and 1529 double UCBT as reported to CIBMTR, following either a myeloablative (N = 1752) or reduced intensity conditioning (N = 759) for acute myeloid leukemia, acute lymphoid leukemia, or myelodysplasia. The primary outcome was 2-year OS. Secondary outcomes included disease free survival, transplant related mortality (TRM), acute and chronic graft vs host disease (GVHD), and GVHD free, relapse free survival (GRFS).

RESULTS

For 1705 adults, in univariate analysis, 2-year OS was 41.5% (99% CI, 37.6 to 45.3) for Whites, 36.1% (99% CI, 28.2 to 44.5) for Latinx, 45.8% (99% CI, 36.7 to 55.1) for Blacks, and 44.5% (99% CI, 33.6 to 55.6) for Asians. In multivariate analysis of adults, Latinx patients had inferior OS compared to black patients (p = .0005, HR 1.45, 99% CI 1.18 to 1.79). OS improved over time for all racial/ethnic groups. GVHD rates were comparable among the different racial/ethnic groups. In the 807 children, the 2-year OS in univariate analysis was 66.1% (99% CI, 59.7 to 72.2) for Whites, 57.1% (99%CI, 49 to 64.9) for Latinx, 46.8% (99%CI, 35.3 to 58.4) for Blacks, and 53.8% (99%CI, 32.7 to 74.2) for Asians. In multivariate analysis, no difference in OS was observed among racial/ethnic groups (p = .051). Grade III/IV acute GVHD was higher in Blacks compared with Whites (p = .0016, HR 2.25, 99% CI 1.36 to 3.74) and Latinx (p = .0016, HR 2.17, 99% CI 1.43 to 3.30). There was no survival advantage to receiving a UCB unit from a donor of similar race and ethnicity, for any racial/ethnic groups, for both children and adults. Black and Latinx adult patients were more likely to live in areas defined as high poverty. Patients from high poverty level areas had worse OS (p = .03), due to a higher rate of TRM (p=0.04). Educational level, and type of insurance did not impact overall survival, GVHD, TRM or other transplant outcomes. Children from areas with a higher poverty level had higher TRM, regardless of race and ethnicity (p = .02). Public health insurance, such as Medicaid, was also associated with a higher TRM (p = .02). However, poverty did not impact pediatric OS, DFS, or other post-transplant outcomes.

CONCLUSIONS

OS for UCBT has improved over time. In adults, OS is comparable among Whites, Blacks, and Asians and lower for Latinx patients. In children, OS is comparable among Whites, Blacks, Latinx, and Asians, but Grade III/IV acute GVHD was higher in Black patients. There was no survival benefit to matching UCB unit and patient by race and ethnicity for adults and children.

Disease progression, treatments, hospitalization, and clinical outcomes in acute GVHD: a multicenter chart review

Acute graft-versus-host disease (GVHD) remains a barrier to successful allogeneic hematopoietic cell transplantation (HCT) outcomes. This multicenter, retrospective chart review describes disease progression, treatment patterns, hospitalizations, and clinical outcomes among 475 patients (≥12 years old) who developed grades II–IV acute GVHD after their first HCT (January 2014–June 2016). Median (interquartile range) age at HCT was 55 (44–63) years. From the date of acute GVHD diagnosis, 190 patients (40.0%) experienced progression to more severe disease and/or developed new organ involvement. Among 431 patients with grades II–IV acute GVHD at diagnosis, 73.1% received first-line systemic corticosteroids. During follow-up (median 524 days since acute GVHD diagnosis), 23.4% of patients had an increase in steroid dose and 44.4% were unable to taper below 10 mg/day. Over half of patients (54.9%) required ≥1 hospital readmission within 100 days post-HCT (≥2 readmissions in 22.3%); mean inpatient length of stay upon readmission was 27.5 days. Approximately half of patients (52.8%) died during follow-up; 1-year overall mortality from date of acute GVHD diagnosis and nonrelapse mortality rates were 35.2% and 25.5%, respectively. Overall, patients who developed acute GVHD following HCT had poor clinical outcomes, highlighting the unmet need for early and effective treatment strategies.

Disease progression, hospital readmissions, and clinical outcomes for patients with steroid-refractory acute graft-versus-host disease: A multicenter, retrospective study

Acute graft-versus-host disease (GVHD) is a significant cause of morbidity and mortality following allogeneic hematopoietic cell transplantation (HCT). This analysis of 168 patients (mean age, 54.8 years) from a multicenter, retrospective chart review describes the clinical course, treatment patterns, hospitalizations, and clinical outcomes of patients aged ≥12 years who developed grades II–IV acute GVHD after their first allogeneic HCT (January 1, 2014, to June 30, 2016) and were refractory to or dependent on corticosteroids. Between diagnosis and maximum grade (median, 6.0 days), 53.6% of patients had new organ involvement, particularly lower gastrointestinal tract acute GVHD, or an increase in acute GVHD grade. Eighty-nine patients (53.0%) received additional systemic GVHD therapy (after systemic corticosteroids) within a median of 21.0 days. Hospital readmission(s) was required for 56.5% of patients within 100 days post-HCT (mean inpatient length of readmission stay, 49.5 days); 24.4% had ≥2 readmissions within 100 days post-HCT. From the date of acute GVHD diagnosis, 70.2% of patients died at a median (interquartile range) of 117.5 (49–258) days. In summary, steroid-refractory and steroid-dependent acute GVHD is associated with a rapidly worsening clinical course that leads to high readmission and mortality rates, emphasizing the need for effective and tolerable therapies.

Infusion of Non-HLA-Matched Off-the-Shelf Ex Vivo Expanded Cord Blood Progenitors in Patients Undergoing Cord Blood Transplantation: Result of a Phase II Clinical Trial

Recipients of myeloablative cord blood transplants (CBT) are known to experience delayed hematopoietic recovery and an increased risk of transplant related mortality (TRM). We developed methods for ex vivo expansion and cryopreservation of CB stem and progenitor cells. 15 patients with hematologic malignancies were enrolled in this single center phase II trial between September 2010 and August 2012 to assess the safety of infusing a non-HLA-matched expanded CB product to bolster a conventional CBT. On the day of transplant, an infusion of the expanded CB product followed the primary graft (1 or 2 unmanipulated CB units). All patients engrafted. Median time to neutrophil and platelet recovery was 19 and 35 days, respectively. Early myelomonocytic recovery was almost entirely due to cells arising from the non-HLA-matched expansion product and were no longer detected at day 14 in all but 2 patients. The probability of 3-years disease free survival was 86%. No TRM was observed throughout the study period, and only 2 patients relapsed. All patients presented with grade II acute graft-versus-host disease (aGVHD) at a median time of 32 days, with no grade III-IV aGVHD observed. At 2 years only 2 patients remain on immunosuppressive therapy for mild chronic GVHD. This phase II safety study demonstrate that infusion of an off-the-shelf non-HLA-matched expanded CB product in addition to a conventional CB graft was safe and led to sustained myeloid recovery. Based on these encouraging results, a prospective multicenter randomized trial utilizing this product has been conducted and results will be soon released. ClinicalTrials.gov Identifier: NCT01175785.

Guidelines for Pediatric Unrelated Cord Blood Transplantation-Unique Considerations

Cord blood (CB) is the stem cell source of choice for approximately 30% of pediatric patients undergoing hematopoietic cell transplantation. Cord blood is readily available and is a particularly appealing stem cell source for patients who lack appropriate HLA-matched related or unrelated donors. Pediatric cord blood transplant (CBT) recipients have low rates of disease relapse in the malignant setting and very low rates of chronic graft-versus-host disease (GVHD). In addition, CB has unique properties that make it the stem cell source of choice for some nonmalignant conditions such as metabolic disorders. This review provides evidence-based and experience-based pediatric-specific guidelines for CBT including considerations for infectious disease management, CB unit selection and infusion, conditioning regimen selection, and GVHD management. In addition, it covers unique bedside considerations for pediatric patients and CB banking. In concert with the other topic specific CB guidelines previously published in this series, it provides a comprehensive overview of the clinical management of pediatric CBT.

Guidelines for Adult Patient Selection and Conditioning Regimens in Cord Blood Transplant Recipients with Hematologic Malignancies and Aplastic Anemia

For cord blood transplantation (CBT), appropriate patient and conditioning regimen selection is necessary to achieve long-term disease-free survival. This review aims to provide comprehensive guidelines on these issues using evidence from the literature and experience at dedicated CBT centers. Topics include patient and disease characteristics that make CBT a good or poor choice and a review of outcomes in commonly used conditioning regimens in CBT. This is accompanied with recommendations on regimen intensity based on disease, organ function, and patient performance status and age. In addition, the use of antithymocyte globulin in CBT is discussed, as is the choice of conditioning in aplastic anemia patients who have access to acceptable CB units.

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.

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.

Engraftment kinetics after transplantation of double unit cord blood grafts combined with haplo-identical CD34+ cells without antithymocyte globulin

Double unit cord blood (dCB) transplantation (dCBT) is associated with high engraftment rates but delayed myeloid recovery. We investigated adding haplo-identical CD34+ cells to dCB grafts to facilitate early haplo-identical donor-derived neutrophil recovery (optimal bridging) prior to CB engraftment. Seventy-eight adults underwent myeloablation with cyclosporine-A/mycophenolate mofetil immunoprophylaxis (no antithymocyte globulin, ATG). CB units (median CD34+ dose 1.1 × 10⁵/kg/unit) had a median 5/8 unit-recipient human leukocyte antigen (HLA)-match. Haplo-identical grafts had a median CD34+ dose of 5.2 × 10⁶/kg. Of 77 evaluable patients, 75 had sustained CB engraftment that was mediated by a dominant unit and heralded by dominant unit-derived T cells. Optimal haplo-identical donor-derived myeloid bridging was observed in 34/77 (44%) patients (median recovery 12 days). Other engrafting patients had transient bridging with second nadir preceding CB engraftment (20/77 (26%), median first recovery 12 and second 26.5 days) or no bridge (21/77 (27%), median recovery 25 days). The 2 (3%) remaining patients had graft failure. Higher haplo-CD34+ dose and better dominant unit-haplo-CD34+ HLA-match significantly improved the likelihood of optimal bridging. Optimally bridged patients were discharged earlier (median 28 versus 36 days). ATG-free haplo-dCBT can speed neutrophil recovery but successful bridging is not guaranteed due to rapid haplo-identical graft rejection.