Anti-thymocyte globulin improves survival free from relapse and graft-versus-host disease after allogeneic peripheral blood stem cell transplantation in patients with Philadelphia-negative acute lymphoblastic leukemia: An analysis by the Acute Leukemia Working Party of the EBMT

Unsupervised Clustering Analysis of Regimen and HLA Characteristics in Pediatric Umbilical Cord Blood Transplantation

HLA matching is a critical factor in allogeneic unrelated hematopoietic cell transplantation (HCT) because of its impact on post-transplantation survival and quality of life. Umbilical cord blood transplantation (UCBT) offers unique advantages, but determining the optimal approach to graft selection and immunosuppression remains challenging. Unsupervised clustering, a machine learning technique, has potential for analyzing transplantation outcomes, but its application in investigating leukemia outcomes has been limited. This study aimed to identify optimal combinations of HLA/ killer immunoglobulin receptor (KIR) donor-patient pairing, conditioning, and immunosuppressive regimens in pediatric patients with acute lymphoblastic leukemia (ALL) or acute myeloblastic leukemia (AML) undergoing UCBT. Outcome data for single, unmanipulated UCBT in pediatric AML (n = 708) and ALL (n = 1034) patients from the Eurocord/EBMT registry were analyzed using unsupervised clustering. Resulting clusters were used to inform post hoc competing risks and Kaplan-Meier analyses. In AML, single HLA-C mismatches with other loci fully matched (7/8) were associated with poorer relapse-free survival (RFS) (P = .039), but a second mismatch at any other locus counteracted this effect. In ALL, total body irradiation (TBI) effectively prevented relapse mortality (P = .007). KIR/HLA-C match status affected RFS in AML (P = .039) but not in ALL (P = .8). Administration of antithymocyte globulin (ATG) substantially increased relapse, with no relapses occurring in the 85 patients who did not receive ATG. Our unsupervised clustering analyses generate several key statistical and mechanistic hypotheses regarding the relationships between HLA matching, conditioning regimens, immunosuppressive therapies, and transplantation outcomes in pediatric AML and ALL patients. HLA-C and KIR combinations significantly impact RFS in pediatric AML but not in ALL. ATG use in fully matched pediatric patients is associated with late-stage relapse. TBI regimens appear to be beneficial in ALL, with efficacy largely independent of histocompatibility variables. These findings reflect the distinct genetic and biological profiles of AML and ALL.

Prognostic factors impacting post-transplant outcomes in adult T-cell acute lymphoblastic leukemia: a registry-based study by the EBMT acute leukemia working party

T-cell acute lymphoblastic leukemia (T-ALL) predominantly affects individuals in late childhood and young adulthood. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative modality particularly in the setting of poor risk genetics and/or persistent minimal residual disease. Limited studies have directly explored the impact of patient- and transplant-related factors on post-transplant outcomes in T-ALL. Using a large dataset from the European Society for Blood and Marrow Transplantation registry, we identified 1907 adult T-ALL patients (70% male) who underwent their first allo-HSCT in first complete remission (CR1) from matched sibling donors (MSD; 45%), unrelated donors (UD; 43%) or haploidentical donors (12%) between 2010 and 2021. The median age at transplant was 33.4 years (18.1-75). The median follow up was 2.9 years. Most patients underwent total body irradiation (TBI)-based myeloablative conditioning (69%). The 2-year overall survival (OS) was 69.4%, and leukemia -free survival (LFS) was 62.1%. In multivariate analysis, advanced age at transplant negatively affected LFS (for each 10-year increment, HR = 1.11, p = 0.004), GVHD-free, relapse-free survival (GRFS) (HR = 1.06, p = 0.04), OS (HR = 1.12, p = 0.002), and non-relapse mortality (NRM) (HR = 1.23, p < 0.001). More recent years of allo-HSCT were associated with improved GFRS (For each 3-year increment, HR = 0.89, p < 0.001), OS (HR = 0.9, p = 0.02), and decreased NRM (HR = 0.82, p = 0.008). TBI improved LFS. (HR = 0.79, p = 0.02), GRFS (HR = 0.83, p = 0.04), and relapse incidence (RI) (HR = 0.65, p < 0.001). Female-to-male transplant negatively affected GRFS (HR = 1.21, p = 0.02) and OS (HR = 1.23, p = 0.048). In vivo T-cell depletion significantly improved GFRS (HR = 0.74, p < 0.001). This large study identified prognostic factors, such as age at transplant conditioning regimen, in influencing post-transplant in adult T-ALL patients undergoing allo-HSCT. Importantly, a significant improvement over time was noted. These findings hold great promise for new adapted treatment strategies and can serve as a benchmark for future studies in that setting.

Management of ALL in adults: 2024 ELN recommendations from a European expert panel

ABSTRACT

Experts from the European Leukemia Net (ELN) working group for adult acute lymphoblastic leukemia have identified an unmet need for guidance regarding management of adult acute lymphoblastic leukemia (ALL) from diagnosis to aftercare. The group has previously summarized their recommendations regarding diagnostic approaches, prognostic factors, and assessment of ALL. The current recommendation summarizes clinical management. It covers treatment approaches, including the use of new immunotherapies, application of minimal residual disease for treatment decisions, management of specific subgroups, and challenging treatment situations as well as late effects and supportive care. The recommendation provides guidance for physicians caring for adult patients with ALL which has to be complemented by regional expertise preferably provided by national academic study groups.

How I treat newly diagnosed acute lymphoblastic leukemia

Treatment algorithms differ for adult patients with Philadelphia-negative (Ph-) and Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL). For Ph- ALL intensive induction-consolidation chemotherapy using "pediatric-inspired" protocols is a standard of care. Allogeneic hematopoietic cell transplantation (allo-HCT) from either an HLA-matched sibling, unrelated or haploidentical donor should be considered for patients with high estimated risk of relapse. Inadequate response at the level of measurable residual disease (MRD) is the strongest adverse prognostic factor. Patients with B-ALL and detectable MRD should be treated with blinatumomab. In the future, the use of blinatumomab and/or inotuzumab ozogamycin in addition to first-line chemotherapy may become a new standard of care reducing the role of allo-HCT. For patients with Ph+ ALL, tyrosine kinase inhibitors (TKI) are the most important components of treatment protocols, while the intensity of chemotherapy may be reduced. Allo-HCT is recommended for all patients treated with imatinib along with low-intensity chemotherapy. Results of phase-II studies using front-line dasatinib or ponatinib in sequence or in combination with blinatumomab are very promising. Such a strategy may allow the avoidance of systemic chemotherapy. The future role of allo-HCT in this context appears uncertain.

Posttransplant cyclophosphamide versus antithymocyte globulin in patients with acute lymphoblastic leukemia treated with allogeneic hematopoietic cell transplantation from matched unrelated donors: A study from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

BACKGROUND

The aim of this study was to compare two immunosuppressive strategies, based on the use of either rabbit antithymocyte globulin (ATG) or posttransplant cyclophosphamide (PTCY), as a prophylaxis of graft-versus-host disease (GVHD) for patients with acute lymphoblastic leukemia (ALL) in first complete remission who underwent hematopoietic cells transplantation from matched unrelated donors.

METHODS

Overall, 117 and 779 adult patients who received PTCY and ATG, respectively, between the years 2015 and 2020 were included in this retrospective study. The median patient age was 40 and 43 years in the PTCY and ATG groups, respectively, and 37% and 35% of patients, respectively, had Philadelphia chromosome-positive ALL.

RESULTS

In univariate analysis, the cumulative incidence of acute and chronic GVHD did not differ significantly between the study groups. The cumulative incidence of relapse at 2 years was reduced in the PTCY group (18% vs. 25%; p = .046) without a significant impact on nonrelapse mortality (11% vs. 16% in the ATG group; p = .29). The rates of leukemia-free survival (LFS) and overall survival were 71% versus 59%, respectively (p = .01), and 82% versus 74%, respectively (p = .08). In multivariate analysis, the receipt of ATG compared with PTCY was associated with a reduced risk of extensive chronic GVHD (hazard ratio, 0.54; 95% confidence interval, 0.3-0.98; p = .04) and an increased risk of low LFS (hazard ratio, 1.57; 95% confidence interval, 1.01-2.45; p = .045).

CONCLUSIONS

The receipt of ATG compared with PTCY, despite the reduced risk of extensive chronic GVHD, is associated with inferior LFS in adults with ALL who undergo hematopoietic cell transplantation from 10/10 human leukocyte antigen-matched unrelated donors. These findings warrant verification in prospective trials.

The role of anti-thymocyte globulin in allogeneic stem cell transplantation (HSCT) from HLA-matched unrelated donors (MUD) for secondary AML in remission: a study from the ALWP /EBMT

We compared outcomes, of 1609 patients with secondary acute myeloid leukemia (sAML) undergoing allogeneic transplantation (HSCT) in first complete remission (CR1) from matched unrelated donors (MUD) from 2010 to 2021, receiving or not receiving anti-thymocyte globulin (ATG) (ATG-1308, no ATG-301). Median age was 60.9 (range, 18.5-77.8) and 61.1 (range, 21.8-75.7) years, (p = 0.3). Graft versus host disease (GVHD) prophylaxis was cyclosporin-A with methotrexate (41%) or mycophenolate mofetil (38.2%), without significant differences between groups. Day 28, engraftment (ANC > 0.5 × 109/L) was 92.3% vs 95.3% (p = 0.17), respectively. On multivariate analysis, ATG was associated with lower incidence of grade II-IV and grade III-IV acute GVHD (p = 0.002 and p = 0.015), total and extensive chronic GVHD (p = 0.008 and p < 0.0001), and relapse incidence (RI) (p = 0.039), while non-relapse mortality (NRM) did not differ (p = 0.51). Overall survival (OS), and GVHD-free, relapse-free survival (GRFS) were significantly higher in the ATG vs no ATG group, HR = 0.76 (95% CI 0.61-0.95, p = 0.014) and HR = 0.68 (95% CI 0.57-0.8, p < 0.0001), with a tendency for better leukemia-free survival (LFS), HR = 0.82 (95% CI 0.67-1, p = 0.051). The main causes of death were the original disease, infection, and GVHD. In conclusion, ATG reduces GVHD and improves LFS, OS, and GRFS in sAML patients without increasing the RI, despite sAML being a high-risk disease.

Fludarabine or cyclophosphamide in combination with total body irradiation as myeloablative conditioning prior to allogeneic hematopoietic cell transplantation for acute lymphoblastic leukemia: an analysis by the Acute Leukemia Working Party of the EBMT

In this registry-based study we retrospectively compared outcomes of allogeneic hematopoietic cell transplantation (allo-HCT) for adult patients with acute lymphoblastic leukemia (ALL) following conditioning with total body irradiation (TBI) combined with either cyclophosphamide (Cy) or fludarabine (Flu). TBI 12 Gy + Cy was used in 2105 cases while TBI 12 Gy + Flu was administered to 150 patients in first or second complete remission. In a multivariate model adjusted for other prognostic factors, TBI/Cy conditioning was associated with a reduced risk of relapse (HR = 0.69, p = 0.049) and increased risk of grade 2-4 acute graft-versus-host disease (GVHD, HR = 1.57, p = 0.03) without significant effect on other transplantation outcomes. In a matched-pair analysis the use of TBI/Cy as compared to TBI/Flu was associated with a significantly reduced rate of relapse (18% vs. 30% at 2 years, p = 0.015) without significant effect on non-relapse mortality, GVHD and survival. We conclude that the use of myeloablative TBI/Cy as conditioning prior to allo-HCT for adult patients with ALL in complete remission is associated with lower risk of relapse rate compared to TBI/Flu and therefore should probably be considered a preferable regimen.

Autologous versus allogeneic hematopoietic cell transplantation for older patients with acute lymphoblastic leukemia. An analysis from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Allogeneic hematopoietic cell transplantation (allo-HCT) with reduced intensity conditioning (RIC) is an option for elderly patients with acute lymphoblastic leukemia (ALL). We retrospectively compared results of RIC-allo-HCT from either a matched sibling donor (MSD, n = 209) or matched unrelated donor (MUD, n = 209) with autologous (auto, n = 142) HCT for patients aged 55 years or more treated in first complete remission (CR1) between 2000 and 2018. The probabilities of leukemia-free survival (LFS) at 5 years were 34% for RIC-allo-HCT versus 39% for auto-HCT (p = 0.11) while overall survival (OS) rates were 42% versus 45% (p = 0.23), respectively. The incidence of relapse (RI) and non-relapse mortality (NRM) was 41% versus 51% (p = 0.22) and 25% versus 10% (p = 0.001), respectively. In a multivariate model, using auto-HCT as reference, the risk of NRM was increased for MSD-HCT (Hazard ratio [HR] = 2.1, p = 0.02) and MUD-HCT (HR = 3.08, p < 0.001), which for MUD-HCT translated into a decreased chance of LFS (HR = 1.55, p = 0.01) and OS (HR = 1.62, p = 0.008). No significant associations were found with respect to the risk of relapse. We conclude that for patients with ALL in CR1, aged above 55 years, auto-HCT may be considered a transplant option alternative to RIC-allo-HCT, although its value requires verification in prospective trials.

Post-transplantation Cyclophosphamide, Tacrolimus and Low-Dose ATG as GVHD Prophylaxis for Allogeneic Peripheral Stem Cell Transplantation for Adult Patients With Lymphoid Malignancies: A Single Arm Phase II Study

The PT-Cy was considered as one of the mainstay protocol for graft verus host disease (GVHD) prophylaxis. Recent study demonstrated that PT-Cy combined with other immunosuppressants could further reduce the incidence of GVHD and improve the GVHD and relapse free survival (GRFS). In this prospective phase II study, we evaluated the effect of a new GVHD prophylaxis consist of PT-Cy combined with tacrolimus and low dose anti-thymoglobulin (ATG). A total of 23 patients were enrolled including 20 patients with acute lymphoblastic leukemia (ALL) and three patients with T cell lymphoma. The median age was 29 years (range, 16~58 years). Patients with HLA-matched related donor (MSD, n=7) received PT-Cy combined with tacrolimus, while patients with HLA matched unrelated (MUD, n = 2) or haplo-identical (Haplo, n = 14) donor received additional ATG at 2.5 mg/kg on day 15 or day 22 after engraftment of neutrophils. As to the acute GVHD (aGVHD), only three patients developed grade I (n = 1) or grade II (n = 2) aGVHD with 100-day incidence of all aGVHD and II-IV aGVHD at 13.0 ± 5.1% and 9.1 ± 6.1% respectively. Only two patients had mild and one had moderate chronic GVHD (cGVHD), with 1-year incidence of cGVHD and moderate/severe cGVHD at 15.2 ± 8.7% and 4.6 ± 4.4% respectively. A high incidence of CMV reactivation was documented (14/16 with MUD/Haplo donor and 2/7 with MSD) with only 1 CMV disease documented. There were two EBV reactivation without post-transplantation lymphoproliferative disease (PTLD) documented. With a median follow-up of 303 days (range, 75~700 days), three patients relapsed leading to 1-year cumulative incidence of relapse (CIR) at 12.8 ± 9.2%. Only one patient died of CMV pneumonia on day 91 with both 100-day and 1-year non-relapse mortality (NRM) at 4.6 ± 4.4%. The 1-year overall survival (OS), event-free survival (EFS) and GRFS were 95.5 ± 4.4%, 82.6 ± 9.5%, and 68.0 ± 11.3% respectively. Based on Simon's stage II design, our primary data showed that the PT-Cy+tacrolimus ± ATG protocol was promising in preventing aGVHD and cGVHD, which may translate into low NRM without increased CIR. Further clinical trial with large number of patients should be warranted. This trial was registered at www.clinicaltrials.gov as #NCT04118075.

Role of antithymocyte globulin in matched sibling donor peripheral blood stem cell transplantation for hematologic malignancies

BACKGROUND

High incidence of chronic graft-versus-host disease (GVHD) has been a major drawback of matched sibling donor peripheral blood stem cell transplantation (MSD -PBSCT). This study aimed to investigate the safety and efficacy of antithymocyte globulin (ATG) as a standardized part of GVHD prophylaxis in patients receiving MSD -PBSCT.

METHODS

A total of 72 patients with hematological malignancies receiving MSD -PBSCT who displayed similar baseline characteristics were either given rabbit ATG ( n = 42) or no ATG (n = 30), in addition to cyclosporine, methotrexate, and mycophenolate mofetil as a standard GVHD prophylaxis regimen. Either patients or donors aged ≥40 years were included in the study. Thymoglobulin was administered at a daily dose of 1.5 mg/kg on day -5 and 3.5 mg/kg on day -4 prior to transplant (the total dose was 5 mg/kg).

RESULTS

After a median follow-up of 874 days, the 3-year cumulative incidence of chronic GVHD (cGVHD) was 37.3% in the ATG group and 52.1% in the non -ATG group. The 3-year overall and disease-free survival probability were 71.0% and 62.0% (ATG versus non -ATG, P = .262) and 66.7% and 58.4% (ATG versus non -ATG, P = .334). No difference was found in the 2-year cumulative incidence of nonrelapse mortality and relapse between the ATG and non -ATG groups. This significant reduction in the incidence of cGVHD without increased relapse risk and nonrelapse mortality led to a 3-year GVHD-free, relapse-free survival probability of 66.7% and 40.0% in the ATG and non-ATG groups, respectively.

CONCLUSIONS

These data suggested that rabbit antithymocyte globulin in the current protocol for GVHD prophylaxis was well tolerable and efficacious.The clinical trial was registered on January 1, 2016 (ClinicalTrials.gov Identifier NCT02677181). https://clinicaltrials.gov/ct2/show/NCT02677181.

Long-term outcomes and risk factor analysis of steroid-refractory graft versus host disease after hematopoietic stem cell transplantation

Steroid-refractory graft versus host disease (GVHD) represents a fearsome complication after allogeneic hematopoietic stem cell transplantation (HSCT). We conducted a retrospective study on outcomes and risk factors associated with acute and chronic steroid-refractory GVHD in a large cohort of 1207 patients receiving HSCT in Saint Louis Hospital between 2007 and 2017. Among patients who developed an acute and/or a chronic GVHD, the cumulative incidences of acute and chronic steroid-refractory disease were 31% and 48%, respectively, at day +100 and 1-year post-HSCT. Through a multivariable analysis we selected several risk factors associated with the development of a steroid-refractory disease. For acute GVHD steroid refractoriness, we identified (1) a very high disease risk index, (2) an unrelated donor, (3) the absence of in vivo T-depletion as GVHD prophylaxis, and (4) a reduced intensity conditioning regimen. For chronic GVHD, (1) the use of peripheral blood stem cells, (2) unrelated donors, and (3) absence of in vivo T-depletion were more likely associated with a steroid-refractory disease. After the construction of a multistate dynamic model, we found that the probability of being alive without relapse after the resolution of all GVHD episodes was about 36% in the long term.

Fludarabine and intravenous busulfan conditioning with post-transplantation cyclophosphamide for allogeneic peripheral stem cell transplantation for adult patients with lymphoid malignancies: a prospective single-arm phase II study

Post-transplantation cyclophosphamide (PT-Cy) alone or in combination with other immunosuppressive drugs has emerged as a promising strategy in the setting of allogeneic hematopoietic stem cell transplantation. Improved survival rate was reported in lymphoid malignancies following PT-Cy strategy compared with myeloid disease in non-myeloablative bone marrow transplant setting. Thus, we aimed to evaluate the safety and efficacy of PT-Cy combined with cyclosporine as graft-versus-host disease (GVHD) prophylaxis after myeloablative conditioning and T cell-replete peripheral stem cell transplantation in lymphoid malignancies. This single-arm phase II clinical trial (NCT01435447) involving 31 adult patients was conducted from January 2013 to June 2018. The donor-type neutrophil engraftment rate was 100%, and the overall incidence of grade II to IV and grade III to IV acute GVHD was 39% and 24%, respectively. The cumulative incidence rates of chronic GVHD (35%), including moderate to severe forms (10%), were reduced compared with those of the historical group (P = 0.03 and P = 0.04, respectively). With a median follow-up of 18 months, the estimated 2-year overall and event-free survival was 64.8% (95% confidence interval: 47.8%-86.7%) and 58.4% (95% CI: 41.9%-81.7%), respectively. The 2-year cumulative incidence rate of relapse was 19.5% (95% CI: 9.0%-35.8%), whereas the non-relapse mortality rate was 21.8% (95% CI: 11.3%-38.1%). These results demonstrated the feasibility of PT-Cy as GVHD prophylaxis in this clinical setting. This strategy could significantly reduce the incidence of chronic GVHD and its moderate to severe forms but not of acute GVHD and results in similar survival outcomes compared with the historical group. A prospective study with additional patients is warranted to confirm the role of PT-Cy in lymphoid malignancy.

Anti-Thymocyte Globulin Prophylaxis Induces a Decrease in Naive Th Cells to Inhibit the Onset of Chronic Graft-versus-Host Disease: Results from the Canadian Bone Marrow Transplant Group (CBMTG) 0801 Study

Anti-thymocyte globulin (ATG) is an established approach to decrease chronic GVHD (cGVHD), yet the exact mechanism is uncertain. To better understand the mechanism of action of ATG in preventing cGVHD, we evaluated the day 100 immune reconstitution of known cGVHD cellular biomarkers using patients from the randomized Canadian Bone Marrow Transplant Group (CBMTG) 0801 trial, which demonstrated a significant impact of ATG on cGVHD. In a separate companion biology study, we evaluated the impact of ATG prophylaxis on cGVHD cellular markers at day 100 in 40 CBMTG 0801 patients. Analysis focused on previously identified cGVHD cellular biomarkers, including naive helper T (Th) cells, recent thymic emigrant (RTE) Th cells, CD21^low B cells, CD56^bright NK_reg cells, and T_reg cells ST2, osteopontin, soluble B-cell activating factor (sBAFF), Interleukin-2 receptor alpha (sCD25), T-cell immunoglobulin and mucin domain-3 (TIM-3), matrix metallopeptidase 3, ICAM-1, C-X-C motif chemokine 10 (CXCL10), and soluble aminopeptidase N. The ATG-treated group had a >10-fold decrease in both RTE naive Th and naive Th cells (P < .0001) and a 10-fold increase in CD56^bright NK_reg cells (P < .0001). T_reg cells, conventional Th cells, CD21^low B cells, and all plasma markers were not affected. In the populations most affected by ATG, changes in naive Th cells were associated with the later development of cGVHD. This analysis suggests that ATG primarily impacts on cGVHD through suppression of naive Th cell expansion after transplantation. These associations need to be validated in additional studies.

Personalizing rabbit anti-thymocyte globulin therapy for prevention of graft-versus-host disease after allogeneic hematopoietic cell transplantation: is there an optimal dose?

The efficacy of anti-thymocyte globulin (ATG) as prophylaxis for graft-versus-host disease (GVHD) has been investigated by many clinical studies over the past decade, including some randomized controlled trials. Intriguingly, although ATG is commonly used as prophylaxis for GVHD, there is still controversy about the optimal dose of ATG for prophylaxis of GVHD after allogeneic hematopoietic cell transplantation (allo-HCT). Indeed, the dose and formulation of ATG, as well as the degree of clinical benefit, has varied among studies, which makes it difficult to fully determine the clinical benefit of ATG. The aim of this review is to summarize the information regarding the optimal ATG dose of each formulation according to stem cell source, and to discuss how best to determine the personalized optimal dose of ATG in each allo-HCT recipient.

Treatment of Adult Patients with Relapsed/Refractory B-Cell Philadelphia-Negative Acute Lymphoblastic Leukemia

The majority of adult patients affected by B-cell acute lymphoblastic leukemia (B-ALL) will relapse after an initial response, while approximately 20% will display primary resistant disease. Patients suffering from relapsed/refractory B-ALL have a very poor outcome. Allogeneic hematopoietic cell transplantation (HCT) still represents the only curative approach, but is not so frequently feasible, because of patient's fitness, donor availability, and the ability to achieve a remission prior to HCT. The estimated remission rates with conventional cytotoxic agents are around 30%, but they are short-lived. These disappointing results led to the introduction of new immunologic-based treatments-blinatumomab and inotuzumab. They produced a substantial improvement in terms of response rates, with the ability, in most cases, to induce a minimal residual disease (MRD)-negative status. Similarly, T cells engineered to express a CD19-specific chimeric antigen receptor (CAR-T) have yielded sensational results among patients with relapsed/refractory B-ALL, with unexpectedly high MRD-negative complete remissions rates. However, the first studies looking at long-term outcomes after CAR-T infusions told us that a significant fraction of such responses are not durable, and may benefit from a consolidation approach such as an allogeneic HCT.

Hematopoietic stem cell transplantation for adults with Philadelphia chromosome-negative acute lymphoblastic leukemia in first remission: a position statement of the European Working Group for Adult Acute Lymphoblastic Leukemia (EWALL) and the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation (EBMT)

Allogeneic hematopoietic stem cell transplantation (HSCT) in first complete remission is a standard of care for adult patients with Philadelphia chromosome (Ph)-negative acute lymphoblastic leukemia (ALL) and high risk of relapse. However, the stratification systems vary among study groups. Inadequate response at the level of minimal residual disease is the most commonly accepted factor indicating the need for alloHSCT. In this consensus paper on behalf of the European Working Group for Adult Acute Lymphoblastic Leukemia and the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, we summarize available evidence and reflect current clinical practice in major European study groups regarding both indications for HSCT and particular aspects of the procedure including the choice of donor, source of stem cells and conditioning. Finally, we propose recommendations for daily clinical practice as well as for planning of prospective trials.

Antithymocyte globulin improves GVHD-free and relapse-free survival in unrelated hematopoietic stem cell transplantation

Antithymocyte globulin (ATG) is an important component of conditioning regimens to prevent graft-versus-host disease (GVHD) in unrelated hematopoietic stem cell transplantation (HSCT), but the optimal dose of ATG remains unknown. We prospectively analyzed 205 unrelated HSCTs in patients with malignant hematological disorders. HSCTs were classified as follows: HLA-matched transplant without ATG (n = 53, group A), HLA-mismatched transplant treated with 6.0 mg/kg thymoglobulin (n = 77, group B), and HLA-matched transplant treated with 4.5 mg/kg thymoglobulin (n = 75, group C). For groups A and B, the 5-year moderate/severe chronic GVHD rates were 31.9% and 24.2%, the 5-year GVHD-free and relapse-free survival (GRFS) rates were 28.3 and 47%, and the 2-year immunosuppressive therapy (IST)-free survival rates were 8.6% and 40.2% (p = 0.0016), respectively. Furthermore, group C had lower incidences of grade II-IV acute GVHD (18.7%) and 5-year moderate/severe chronic GVHD (16.6%) than group A did. Group C had higher 5-year GRFS (52.1% vs 28.3%, p = 0.002), 2-year IST-free survival (51.7% vs 8.6%, p = 0.00004), and 5-year overall survival (OS) (68.3% vs 41.5%, p = 0.007) rates than group A did. Thus, ATG was associated with better GVHD prevention, a higher rate of IST-free survival, lower transplant-related mortality (TRM), and superior OS and GRFS in unrelated HSCTs.

Assessment of Individual versus Composite Endpoints of Acute Graft-versus-Host Disease in Determining Long-Term Survival after Allogeneic Transplantation

The overall composite of graft-versus-host disease (GVHD)-free, relapse-free survival (GRFS), defined as survival free of grade III-IV acute GVHD (aGVHD), chronic GVHD (cGVHD) requiring systemic immunosuppressive therapy (IST), or relapse, has emerged as a useful composite in clinical trials and to capture clinically meaningful events that impact quantity and quality of survival after allogeneic hematopoietic cell transplantation (HCT). We reviewed 565 consecutive patients aged ≥18 years undergoing HCT for hematologic malignancy to analyze how baseline incidence, specifics of clinical definitions, and proposed reductions in any one individual event may dynamically alter the overall performance of the composite To determine the relative impact of each GRFS event (excluding death), we accounted for competing risks using Fine and Gray methods, and correlated each event with overall survival (OS) using Kaplan-Meier methods. The consequences of modulating individual or composite endpoints on OS, such as hypothesized reductions of events of an HCT interventional trial, were examined using Monte Carlo simulations. The median age of the cohort was 54 years (range, 18 to 73 years). The majority of patients received HLA-matched unrelated donor HCT (53%), consisting of peripheral blood stem cell grafts (90%) after myeloablative conditioning (68%). Relapse conferred the greatest risk for death (hazard ratio [HR], 7.89; 95% confidence interval [CI], 5.83 to 10.69), followed by grade III-IV aGVHD (HR, 6.16; 95% CI, 4.42 to 8.56) and cGVHD requiring IST (HR, 1.69; 95% CI, 1.16 to 2.46). The overall GRFS composite correlated with an HR of 4.81 (95% CI, 3.61 to 6.41), which was lower compared with either relapse or grade III-IV aGVHD. Statistical simulations found that modulating the combined risk of both relapse and grade III-IV aGVHD predicted the greatest change in 5-year OS. These simulations suggest that GRFS as currently defined may be less optimal for correlating with OS, and further refinement of composite endpoints is needed. Nonetheless, composite endpoints may be particularly helpful in mitigating potential difficulties in interpretation when competing risks are present, most commonly seen in HCT studies.

Impact of anti-thymocyte globulin on results of allogeneic peripheral blood stem cell transplantation for patients with Philadelphia-positive acute lymphoblastic leukaemia: An analysis by the Acute Leukemia Working Party of the EBMT

BACKGROUND

Anti-thymocyte globulin (ATG) is widely used to prevent graft-versus-host disease (GVHD) after allogeneic peripheral blood stem cell transplantation (alloPBSCT). The goal of this study was to retrospectively assess the effect of ATG on outcomes in the setting of Philadelphia chromosome-positive acute lymphoblastic leukaemia (Ph+ ALL).

METHODS

In the analysis, 1170 adult patients undergoing alloPBSCT from human leucocyte antigen-matched sibling or unrelated donors in the first complete remission between 2007 and 2016 were included. ATG was used in 429/575 (75%) and 121/595 (20%) patients transplanted from unrelated or sibling donors, respectively.

RESULTS

The incidence of chronic GVHD was 35% for patients treated with ATG compared with 52% in those not receiving ATG (p < 0.001), while the rate of extensive chronic GVHD was 16% and 36%, respectively (p < 0.001). The probability of survival free from GVHD and relapse (GRFS) was 42% and 32%, respectively (p = 0.002). In a multivariate model, the use of ATG was associated with reduced risk of overall chronic GVHD (hazard ratio [HR] = 0.52, p < 0.001) and extensive chronic GVHD (HR = 0.46, p < 0.001). It was also associated with better GRFS (HR = 0.77, p = 0.007), despite increased risk of relapse (HR = 1.41, p = 0.02). No significant effect was found with regard to the risk of non-relapse mortality and overall mortality.

CONCLUSIONS

The use of ATG for patients with Ph+ ALL undergoing alloPBSCT is associated with reduced risk of chronic GVHD without impact on survival and therefore, could be considered. However, increased risk of relapse suggests the need for strict monitoring of minimal residual diseases and appropriate interventions after transplantation.