Long-term prognosis for 1-year relapse-free survivors of CD34+ cell-selected allogeneic hematopoietic stem cell transplantation: a landmark analysis

Fostering next generation transplant physicians

As opposed to the rapid expansion of hematopoietic cell transplantation (HCT) and other cellular therapies (CT), we are now facing a global shortage of transplant physicians and other professionals to support the activity of HCT/CT. To overcome this obstacle, a variety of approaches are now being undertaken in four international HCT societies. This article aims to share their current attempts to foster the next generation of transplant physicians and allied professionals needed to secure the continued global growth of HCT/CT.

The Simplified Comorbidity Index: a new tool for prediction of nonrelapse mortality in allo-HCT

Individual comorbidities have distinct contributions to nonrelapse mortality (NRM) following allogeneic hematopoietic cell transplantation (allo-HCT). We studied the impact of comorbidities individually and in combination in a single-center cohort of 573 adult patients who underwent CD34-selected allo-HCT following myeloablative conditioning. Pulmonary disease, moderate to severe hepatic comorbidity, cardiac disease of any type, and renal dysfunction were associated with increased NRM in multivariable Cox regression models. A Simplified Comorbidity Index (SCI) composed of the 4 comorbidities predictive of NRM, as well as age >60 years, stratified patients into 5 groups with a stepwise increase in NRM. NRM rates ranged from 11.4% to 49.9% by stratum, with adjusted hazard ratios of 1.84, 2.59, 3.57, and 5.38. The SCI was also applicable in an external cohort of 230 patients who underwent allo-HCT with unmanipulated grafts following intermediate-intensity conditioning. The area under the receiver operating characteristic curve (AUC) of the SCI for 1-year NRM was 70.3 and 72.0 over the development and external-validation cohorts, respectively; corresponding AUCs of the Hematopoietic Cell Transplantation-specific Comorbidity Index (HCT-CI) were 61.7 and 65.7. In summary, a small set of comorbidities, aggregated into the SCI, is highly predictive of NRM. The new index stratifies patients into distinct risk groups, was validated in an external cohort, and provides higher discrimination than does the HCT-CI.

Long-term transplant outcomes after allogeneic hematopoietic transplant in pediatric patients with hematological malignancies are influenced by severe chronic graft vs. host disease and immune reconstitution

Long-term follow-up studies are crucial to ensure surveillance and intervention for late complications after allogeneic stem cell transplantation, but they are scarce on the pediatric population. This study aims to analyze risk factors for long-term transplant outcomes. We report a landmark analysis of 162 pediatric patients who underwent allogeneic transplantation between 1991 and 2016, and survived for at least 12 months after the transplant. With a median follow-up time of 10 years for the survivors, the probability of disease-free survival (DFS) and overall survival (OS) is 81 ± 3 and 88 ± 2%, respectively. Variables that influenced DFS in the univariate analysis were: disease phase (early phase 87 ± 3% vs. advanced phase 74 ± 5%; p = 0.04), acute graft vs. host disease (aGvHD; yes 73 ± 5% vs. no 87 ± 3%; p = 0.038), severe chronic GvHD (cGvHD; yes 41 ± 13% vs. no 85 ± 3%; p = 0.0001), and CD4+ lymphocytes 2 years after the transplant (above the median of 837/μl 98 ± 2% vs. below the median 82 ± 6%, p = 0.026). However, in the multivariate analysis, the only variable that influenced DFS was presence of severe chronic GvHD (yes vs. no, HR 6.25; 95% CI, 1.35-34.48; p = 0.02). Transplant strategies should aim to reduce the risk of severe cGvHD. Immune reconstitution surveillance may help clinicians to better deal with late transplant complications.

The post-transplant scoring system (PTSS) is associated with outcomes in patients with MDS after CD34+selected allogeneic stem cell transplant

The post-transplant scoring system (PTSS), developed by the Francophone Society of Bone Marrow Transplantation and Cellular Therapy, is based on three independent post-transplant risk factors: grade of acute graft-versus-host disease, lack of platelet recovery before day 100, and relapse before day 100; discriminating low- (0), intermediate- (1–3), and high-risk (4–8) patients. We investigated the prognostic value of the PTSS in a cohort of patients with MDS who underwent myeloablative CD34-selected TCD transplants. From 2008 to 2018, 109 patients underwent a first TCD-HCT for MDS at our center. We used Cox proportional hazards models and different landmark analyses to evaluate the association of categorized PTSS score risk groups with overall survival (OS). Patients with an intermediate/ high risk PTSS score had decreased OS at day 180 (univariate HR 3.25 [95% CI 1.60, 6.60], p = 0.001) and at day 365 (univariate HR 5.42 [95% CI 2.21, 13.3], p < 0.001) compared to low risk PTSS scores. This association remained significant after adjusting for HCT-CI. PTSS score calculated at day 100 was not associated with OS, even after adjusting for HCT-CI subgroups. In summary, the PTSS predicted survival at day 180 and day 365 in recipients of T-cell-depleted allografts for myelodysplastic syndrome.

Decreased Mortality in 1-Year Survivors of Umbilical Cord Blood Transplant vs. Matched Related or Matched Unrelated Donor Transplant in Patients with Hematologic Malignancies

Allogeneic hematopoietic stem cell transplantation (HCT) has the potential to cure hematologic malignancies but is associated with significant morbidity and mortality. Although deaths during the first year after transplantation are often attributable to treatment toxicities and complications, death after the first year may be due to sequelae of accelerated aging caused by cellular senescence. Cytotoxic therapies and radiation used in cancer treatments and conditioning regimens for HCT can induce aging at the molecular level; HCT patients experience time-dependent effects, such as frailty and aging-associated diseases, more rapidly than people who have not been exposed to these treatments. Consistent with this, recipients of younger cells tend to have decreased markers of aging and improved survival, decreased graft-versus-host disease, and lower relapse rates. Given that umbilical cord blood (UCB) is the youngest donor source available, we studied the outcomes after the first year of UCB transplantation versus matched related donor (MRD) and matched unrelated donor (MUD) transplantation in patients with hematologic malignancies over a 20-year period. In this single-center, retrospective study, we examined the outcomes of all adult patients who underwent their first allogeneic HCT through the Duke Adult Bone Marrow Transplant program from January 1, 1996, to December 31, 2015, to allow for at least 3 years of follow-up. Patients were excluded if they died or were lost to follow-up before day 365 after HCT, received an allogeneic HCT for a disease other than a hematologic malignancy, or received cells from a haploidentical or mismatched adult donor. UCB recipients experienced a better unadjusted overall survival than MRD/MUD recipients (log rank P = .03, median overall survival: UCB not reached, MRD/MUD 7.4 years). After adjusting for selected covariates, UCB recipients who survived at least 1 year after HCT had a hazard of death that was 31% lower than that of MRD/MUD recipients (hazard ratio, 0.69; 95% confidence interval, 0.47-0.99; P = .049). This trend held true in a subset analysis of subjects with acute leukemia. UCB recipients also experienced lower rates of moderate or severe chronic graft-versus-host disease (GVHD) and nonrelapse mortality, and slower time to relapse. UCB and MRD/MUD recipients experienced similar rates of grade 2-4 acute GVHD, chronic GHVD, secondary malignancy, and subsequent allogeneic HCT. UCB is already widely used as a donor source in pediatric HCT; however, adult outcomes and adoption have historically lagged behind in comparison. Recent advancements in UCB transplantation such as the implementation of lower-intensity conditioning regimens, double unit transplants, and ex vivo expansion have improved early mortality, making UCB an increasingly attractive donor source for adults; furthermore, our findings suggest that UCB may actually be a preferred donor source for mitigating late effects of HCT.

A Single-Center, Open-Label Trial of Isavuconazole Prophylaxis against Invasive Fungal Infection in Patients Undergoing Allogeneic Hematopoietic Cell Transplantation

Isavuconazole is a broad-spectrum triazole approved for treatment of invasive fungal infections (IFIs). In this open-label, single-arm study, we evaluated isavuconazole for antifungal prophylaxis after allogeneic hematopoietic cell transplantation (HCT). Adult patients admitted for first HCT received micafungin 150 mg i.v. daily from admission through day +7 (D+7) post-transplantation (±2 days) followed by isavuconazole prophylaxis (i.v./p.o. 372 mg every 8 hours for 6 doses and then 372 mg daily) through maximum D+98 post-HCT. Patients were followed through D+182. The primary endpoint was prophylaxis failure, defined as discontinuation of prophylaxis for proven/probable IFI; systemic antifungal therapy for >14 days for suspected IFI; toxicity leading to discontinuation; or an adverse event. Between June 2017 and October 2018, 99 patients were enrolled in the study, of whom 95 were included in our analysis. The median patient age was 57 years (interquartile range [IQR], 50 to 66 years). Sixty-four (67%) patients received peripheral blood, 17(18%) received bone marrow, and 14 (15%) received a cord blood allograft for acute leukemia (55%), lymphoma (17%), myelodysplastic syndrome (16%), or another hematologic disease (14%). One-third (n = 31; 33%) of patients underwent CD34⁺-selected HCT. Isavuconazole prophylaxis was given for a median of 90 days (IQR, 87 to 91 days). Ten patients (10.7%) met the primary endpoint. Candidemia occurred in 3 patients (3.1%), 1 of whom had grade III skin acute graft-versus-host disease (GVHD). Toxicity leading to discontinuation occurred in 7 patients (7.4%). The most common toxicity was liver function abnormalities in 5 patients, including grade 1 transaminitis in 2 patients and grade 3 hyperbilirubinemia in 3 patients. Four patients (4.2%) had early discontinuation of isavuconazole for reasons not meeting the primary study endpoint. Six patients died during the study period, including 3 during prophylaxis and 3 during follow-up. No deaths were attributed to isavuconazole. The majority (85%) of allogeneic HCT recipients completed isavuconazole prophylaxis according to protocol. The rate of breakthrough candidemia was 3.1%, and there were no invasive mold infections. Our data support the utility of isavuconazole for antifungal prophylaxis after HCT.

Allogeneic Stem Cell Transplantation with CD34+ Cell Selection

The success of allogeneic stem cell transplant is hampered by the development of acute and chronic graft-versus-host disease (GvHD) which has direct impact on treatment-related mortality and morbidity. As a result, T cell depletion through positive selection of CD34+ cells has emerged as a promising strategy to reduce acute and chronic GvHD in these patients.

In this review, we summarize the main characteristics of allogeneic stem cell transplant with CD34+ cell selection including risks of graft failure, GvHD, infection, organ toxicity, and long-term survival. Moreover, we highlight future strategies to improve the results of this platform and to consolidate its use in clinical practice.

Robust Selections of Various Hematopoietic Cell Fractions on the CliniMACS Plus Instrument

Cell separation technologies play a vital role in the graft engineering of hematopoietic cellular fractions, particularly with the rapid expansion of the field of cellular therapeutics. The CliniMACS Plus Instrument (Miltenyi Biotec) utilizes immunomagnetic techniques to isolate hematopoietic progenitor cells (HPCs), T cells, NK cells, and monocytes. These products are ultimately used for HPC transplantation and for the manufacture of adoptive immunotherapies. We evaluated the viable cell recovery and cell purity of selections and depletions performed on the CliniMACS Plus over a 10-year period at our facility, specifically assessing for the isolation of CD34+, CD4+, CD3+/CD56+, CD4+/CD8+, and CD25+ cells. Additionally, patient- and instrument-related factors affecting these parameters were examined. Viable cell recovery ranged from 32.3 ± 10.2% to 65.4 ± 15.4%, and was the highest for CD34+ selections. Cell purity ranged from 86.3 ± 7.2% to 99.0 ± 1.1%, and was the highest for CD4+ selections. Undesired cell fractions demonstrated a range of 1.2 ± 0.45 to 5.1 ± 0.4 log reductions. Red cell depletions averaged 2.12 ± 0.68 logs, while platelets were reduced by an average of 4.01 ± 1.57 logs. Donor characteristics did not impact viable cell recovery or cell purity for CD34+ or CD4+ cell enrichments; however, these were affected by manufacturing variables, including tubing size, bead quantity, and whether preselection platelet washes were performed. Our data demonstrate the efficient recovery of hematopoietic cellular fractions on the CliniMACS Plus that may be optimized by adjusting manufacturing variables.

Establishing a standardized system for review and adjudication of chronic graft-vs-host disease data in accordance with the National Institutes Consensus criteria

GVHD is a frequent complication following allo-HCT. The NIH consensus group established new guidelines for the evaluation of chronic GVHD. However, GVHD assessment remains challenging due its complexity and requirement for laborious evaluation. We, therefore, established a standardized approach for the assessment of chronic GVHD in accordance with the NCC guidelines. At a single institution, all allograft recipients were evaluated for GVHD within the first-year post allo-HCT following a 3-step workflow (real-time assessment, consensus review, and documentation). A GVHD adjudication committee was created and a dynamic electronic GVHD data capture form was developed guiding the clinician through a comprehensive review of systems following the NCC guidelines. We found that the assessment and reporting of GVHD reached 100% compliance. The establishment of an institutional GVHD adjudication committee enabled standardized assessment of GVHD. Our workflow can be adopted by other centers to create a similar framework for dedicated GVHD evaluation.

Expanding Therapeutic Opportunities for Hematopoietic Stem Cell Transplantation: T Cell Depletion as a Model for the Targeted Allograft

Allogeneic hematopoietic cell transplantation is a fundamental part of the treatment of hematologic malignancies and marrow failure syndromes, but complications including graft-versus-host disease, prolonged immune deficiency and infection, and organ toxicities, as well as relapse, remain obstacles to improved overall survival. As the cellular characteristics of the allograft can exert significant impact on outcomes, the development of more strategically designed grafts represents a rich area for therapeutic intervention. We describe the use of ex vivo T cell–depleted grafts as a model for the targeted graft and review evolving knowledge and approaches for further refinement of allografts to improve patient outcomes.

Advances in Ex Vivo T Cell Depletion - Where Do We Stand?

Graft-versus-host (GVHD) is an important cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). As donor T cells are recognized as key drivers of GVHD, some approaches to prevent GVHD have focused on T cell depletion of the allograft. In this review we summarize methods and outcomes of ex vivo T cell depleted (TCD) HCT with a focus on CD34+ selection. This platform is efficacious in preventing acute and chronic GVHD across a wide range of hematologic malignancies, and with the exception of chronic myeloid leukemia, is not associated with adverse relapse or survival outcomes compared to conventional GVHD prophylaxis platforms. In retrospective comparisons recipients of CD34+ selected HCT have higher rates of GVHD-free relapse-free survival (GRFS) than conventional HCT counterparts. Although CD34+ selected allografts require myeloablative and antithymocyte-globulin based conditioning to support engraftment, abrogation of calcineurin inhibitors and methotrexate in this approach reduces its toxicity such that it can be considered in select older and more comorbid patients who could benefit from ablative HCT. A trial comparing GVHD prophylaxis regimens (BMT CTN 1301, NCT02345850) has completed accrual and will be the first to compare CD34+ selected HCT with conventional HCT in a randomized prospective setting. Its findings have potential to establish CD34+ selected HCT as a new standard-of-care platform for GVHD prevention.

Ex vivo and in vivo T cell-depleted allogeneic stem cell transplantation in patients with acute myeloid leukemia in first complete remission resulted in similar overall survival: on behalf of the ALWP of the EBMT and the MSKCC

Background

Graft-versus-host disease (GVHD) is one of the leading causes of non-relapse mortality and morbidity after allogeneic hematopoietic stem cell transplantation (allo-HCT).

Methods

We evaluated the outcomes of two well-established strategies used for GVHD prevention: in vivo T cell depletion using antithymocyte globulin (ATG) and ex vivo T cell depletion using a CD34-selected (CD34+) graft. A total of 525 adult patients (363 ATG, 162 CD34+) with intermediate or high-risk cytogenetics acute myeloid leukemia (AML) in first complete remission (CR1) were included. Patients underwent myeloablative allo-HCT using matched related or unrelated donors.

Results

Two-year overall survival estimate was 69.9% (95% CI, 58.5–69.4) in the ATG group and 67.6% (95% CI, 60.3–74.9) in the CD34+ group (p = 0.31). The cumulative incidence of grade II–IV acute GVHD and chronic GVHD was higher in the ATG cohort [HR 2.0 (95% CI 1.1–3.7), p = 0.02; HR 15.1 (95% CI 5.3–42.2), p < 0.0001]. Parameters associated with a lower GVHD-free relapse-free survival (GRFS) were ATG [HR 1.6 (95% CI 1.1–2.2), p = 0.006], adverse cytogenetic [HR 1.7 (95% CI 1.3–2.2), p = 0.0004], and the use of an unrelated donor [HR 1.4 (95% CI 1.0–1.9), p = 0.02]. There were no statistical differences between ATG and CD34+ in terms of relapse [HR 1.52 (95% CI 0.96–2.42), p = 0.07], non-relapse mortality [HR 0.96 (95% CI 0.54–1.74), p = 0.90], overall survival [HR 1.43 (95% CI 0.97–2.11), p = 0.07], and leukemia-free survival [HR 1.25 (95% CI 0.88–1.78), p = 0.21]. Significantly, more deaths related to infection occurred in the CD34+ group (16/52 vs. 19/112, p = 0.04).

Conclusions

These data suggest that both ex vivo CD34-selected and in vivo ATG T cell depletion are associated with a rather high OS and should be compared in a prospective randomized trial.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0668-3) contains supplementary material, which is available to authorized users.