In vivo T cell depletion with low-dose rabbit antithymocyte globulin results in low transplant-related mortality and low relapse incidence following unrelated hematopoietic stem cell transplantation

Haploidentical- versus identical-sibling transplant for high-risk pediatric AML: A multi-center study

Background

Human leukocyte antigen‐identical sibling donor (ISD)‐hematopoietic stem cell transplantation (SCT) is a potentially curative treatment for high‐risk pediatric acute myeloid leukemia (AML). A haploidentical donor (HID) is readily available to almost all children. Previous studies have demonstrated that patients with HID‐SCT had similar outcomes compared to ISD‐SCT for pediatric and adult AML. However, the role of HID‐SCT in high‐risk pediatric AML is unclear.

Methods

To compare the overall survival of high‐risk AML children who underwent either HID‐SCT or ISD‐SCT, we analyzed 179 cases of high‐risk AML patients under 18 years of age treated with either ISD‐SCT (n = 23) or HID‐SCT (n = 156). Granulocyte colony‐stimulating factor plus anti‐thymocyte globulin‐based regimens were used for HID‐SCT. We also analyzed the subgroup data of AML patients at first complete remission (CR1) before SCT with known cytogenetic risk.

Results

The numbers of adverse cytogenetic risk recipients were 8 (34.8%) and 13 (18.8%) in the ISD‐SCT group and the HID‐SCT group, and the number of patients with disease status beyond CR1 were 6 (26.1%) and 14 (20.3%) in the two groups. The cumulative rates of grades II‐IV acute graft‐versus‐host disease (GVHD) were 13.0% in the ISD‐SCT group and 34.8% in the HID‐SCT group (P = 0.062), with a three‐year cumulative rates of chronic GVHD at 14.1% and 34.9%, respectively (P = 0.091). The relapse rate in the ISD‐SCT group was significantly higher than that in the HID‐SCT group (39.1% vs. 16.4%, P = 0.027); with non‐relapse mortality at 0.0% and 10.6% (P = 0.113), respectively. The three‐year overall survival rates were 73.0% for the ISD‐SCT group and 74.6% for the HID‐SCT group (P = 0.689). In subgroup analysis, the three‐year relapse rate in the ISD‐SCT group was higher than that in the HID‐SCT group (50.0% vs. 9.2%, P = 0.001) and the three‐year DFS in the ISD‐SCT group (50.0%) was lower than that in the HID‐SCT group (81.2%) (P = 0.021).

Conclusions

Unmanipulated HID‐SCT achieved DFS and OS outcomes comparable to those of ISD‐SCT for high‐risk pediatric AML patients with potentially higher rate but manageable GVHD.

HLA disparity is not crucial for the survival rate and severity of chronic health conditions in adult recipients following family donor hematopoietic stem cell transplantation

The shortage of HLA-identical siblings or unrelated donors has restricted the application of hematopoietic stem cell transplantation (HSCT). Few studies have systematically assessed survival and chronic health conditions (CHCs) in the same cohort of patients after HLA-mismatched/haploidentical (mismatched) family donor transplantation. In the present study, we retrospectively analyzed the survival of 127 adult patients receiving either HLA-matched (71 cases) or HLA-mismatched (56 cases) family donor transplantation. Of 127 patients, 81 patients survived at least 2 years after HSCT and were still alive until the present investigation. We evaluated the CHCs in 76 survivors (41 matched and 35 mismatched). CHC-related information was scored according to the Bone Marrow Transplant Survivor Study questionnaire. There was no significant difference in overall survival or disease-free survival between HLA-matched and -mismatched transplant recipients. The CHCs were less severe in HLA-mismatched recipients than in matched cohorts. Multivariate analysis identified that age over 40 years at transplantation and presence of chronic graft-versus-host disease were independent risk factors for CHCs, while anti-thymocyte globulin-containing conditioning regimens might be protective. However, HLA disparity was not crucial for either the survival rate or CHCs. In conclusion, HLA-mismatched family donor transplantation can achieve comparable therapeutic effects to HLA-identical sibling transplantation.

Bone marrow may be the preferable graft source in recipients homozygous for HLA-C group 2 ligands for inhibitory killer Ig-like receptors

HLA class I molecules participate in natural killer cell regulation by acting as ligands for inhibitory killer cell Ig-like receptors (KIRs). One individual may express one or more inhibitory KIR lacking the corresponding HLA ligand. The role of this 'missing KIR ligand' constellation in hematopoietic SCT (HSCT) remains controversial and depends on incompletely defined transplant variables. We have retrospectively analyzed the effects of missing HLA-C group 1/2 and Bw4 KIR ligands in the recipients on the outcome in 382 HSCT, comparing 118 BMT to 264 PBSC transplants (PBSCT). In the multivariate Cox analysis of PBSCT, poor PFS was observed in homozygous HLA-C group 2 (C2/2) recipients (risk ratio (RR), 1.59; P=0.026). In contrast, C2 homozygosity was not unfavorable after BMT (RR, 0.68; P=0.16). C2 homozygous recipients (n=68) had better PFS after BMT than after PBSCT (RR, 0.17; P=0.001), due to fewer relapses (RR, 0.27; P=0.018). Missing Bw4 favorably influenced PFS after BMT (RR, 0.56; P=0.04), but not after PBSCT. These data suggest opposite effects of missing KIR ligands in BMT vs PBSCT. Larger studies are required to reassess whether BMT should be preferred to PBSCT as an option for C2/C2 recipients.

Haploidentical hematopoietic stem cell transplantation in child hematologic malignancies with G-CSF-mobilized marrow grafts without T-cell depletion: a single-center report of 45 cases

In this report, the authors describe a protocol for haploidentical bone marrow transplantation in children who received G-CSF-mobilized bone marrow grafts without T-cell depletion from HLA-mismatched parents. Forty-two of 45 patients achieved complete donor hematopoietic engraftment; the medium time for neutrophil and platelet recovery was 17 and 19 days, respectively. Three died of early transplantation-associated complications; other causes of death included relapse (11 cases), fungal pneumonia (5), and acute graft-versus-host disease (2). The total disease-free survival rate longer than 2 years was 53.3%. These data suggest that haploidentical hematopoietic transplantation is an alterative strategy for children who lack immediate access to HLA-matched sources.

Granzymes A and B serum levels in allo-SCT

Activated cytotoxic T lymphocytes and natural killer cells, which are involved in the pathogenesis of GVHD and viral infections after SCT produce granzymes (Grs). This study performed an ELISA in the serum of 86 patients at various time points before and after Allo-SCT to investigate GrA and GrB levels as potential markers for these serious complications. The increase in Gr levels from the day of transplantation until the appearance of the complication was highly predictive. If GrA increased to three times its pretransplant level, the cumulative incidence of developing acute GVHD was 73% and for CMV infection 68%, in comparison with 45 and 35%, respectively, for patients without these complications. A strong increase in GrA level correlated with clinical severity of acute GVHD. No correlation was observed with early relapse or long-term overall survival. In addition to clinical parameters, a strong increase in GrA levels was identified as an independent marker for the occurrence of acute GVHD as well as for CMV infection. Similar effects were observed with GrB. In conclusion, Gr protein levels can also be used as a marker for complications after Allo-SCT.

Hematopoietic SCT from partially HLA-mismatched (HLA-haploidentical) related donors

Hematopoietic SCT from a partially HLA-mismatched (HLA-haploidentical) first-degree relative offers the benefits of rapid and near universal donor availability but also the risks that result from traversing the HLA barrier; namely, graft failure, severe GVHD and prolonged immunodeficiency. Improvements over the last 10 years in conditioning regimens, graft engineering and pharmacological immunoprophylaxis of GVHD have substantially reduced the morbidity and mortality of HLA-haploidentical SCT. Highly immunosuppressive but nonmyeloablative conditioning extends the availability of HLA-haploidentical SCT to elderly hematologic malignancy patients lacking HLA-matched donors and permits recovery of autologous hematopoiesis in the event of graft failure. Current regimens for HLA-haploidentical SCT are associated with a 2-year non-relapse mortality of 20+/-5%, relapse of 35+/-15% and overall survival of 50+/-20%. Major developmental areas include harnessing natural killer cell alloreactivity to reduce the risk of disease relapse and improving immune reconstitution by delayed infusions of lymphocytes selectively depleted of alloreactive cells. Hematologic malignancy patients who lack suitably matched related or unrelated donors can now be treated with HLA-haploidentical related donor or unrelated umbilical cord blood SCT. Future clinical trials will assess the relative risks and benefits of these two graft sources.

Reduced-intensity allogeneic transplant in patients older than 55 years: unrelated umbilical cord blood is safe and effective for patients without a matched related donor

The lower morbidity and mortality of reduced-intensity conditioning (RIC) regimens have allowed allogeneic hematopoietic cell transplantation (HCT) in older patients. Unrelated umbilical cord blood (UCB) has been investigated as an alternative stem cell source to suitably HLA matched related (MRD) and adult volunteer unrelated donors. We hypothesized that RIC HCT using UCB would be safe and efficacious in older patients, and compared the treatment-related mortality (TRM) and overall survival (OS) of RIC HCT in patients older than 55 years using either MRD (n = 47) or, in patients with no 5 of 6 or 6 of 6 HLA compatible related donors, UCB (n = 43). RIC regimen consisted of total-body irradiation (TBI; 200 cGy) and either cyclophosphamide and fludarabine (n = 69), or busulfan and fludarabine (n = 16) or busulfan and cladribine (n = 5). The median age of MRD and UCB cohorts was 58 (range, 55-70) and 59 (range, 55-69) years, respectively. acute myelogenous leukemia/myelodysplastic syndrome (AML/MDS) (50%) was the most common diagnosis. All MRD grafts were 6 of 6 HLA matched to the recipient. Among patients undergoing UCB HCT, 88% received 2 UCB units to optimize cell dose and 93% received 1-2 HLA mismatched grafts. The median follow-up for survivors was 27 (range: 12-61) months. The 3-year probabilities of progression-free survival (PFS; 30% versus 34%, P = .98) and OS (43% versus 34%, P = .57) were similar for recipients of MRD and UCB. The cumulative incidence of grade II-IV acute graft-versus-host (aGVHD) disease (42% versus 49%, P = .20) and TRM at 180-days (23% versus 28%, P = .36) were comparable. However, UCB recipients had a lower incidence of chronic graft-versus-host disease (cGVHD) at 1 year (40% versus 17%, P = .02). On multivariate analysis, graft type had no impact on TRM or survival, and the HCT comorbidity index score was the only factor independently predictive for these endpoints. Our study supports the use of HLA mismatched UCB as an alternative graft source for older patients who need a transplant but do not have an MRD. The use of RIC and UCB extends the availability of transplant therapy to older patients previously excluded on the basis of age and lack of a suitable MRD. A careful review of existing comorbidities is necessary when considering older patients for HCT.

Vascular Endothelial Growth Factor and Activin-A Serum Levels Following Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation is frequently complicated by syndromes characterized by a disruption of the endothelial integrity such as graft-versus-host disease or liver toxicity. Vascular endothelial growth factor and activin-A, a member of the transforming growth factor beta (TGF-beta) superfamily, are important for endothelial integrity and tissue repair. We retrospectively measured endogenous vascular endothelial growth factor and activin-A serum levels in 70 patients following allogeneic stem cell transplantation. Vascular endothelial growth factor serum levels were significantly decreased within the first 2 weeks after the transplant and returned to pre transplant levels by day +15. Activin-A serum levels were significantly elevated from day +7 with peak levels reached on day +10. By using the median value as cutoff high vascular endothelial growth factor levels on day +15 were associated with significantly better overall survival, less liver toxicity, faster neutrophil recovery, and a trend towards less severe acute graft-versus-host disease. No correlation was found between activin-A serum levels and survival, liver toxicity, neutrophil recovery, or graft-versus-host disease. Monitoring of vascular endothelial growth factor levels following allogeneic hematopoietic stem cell transplantation might help to identify patients with a very high risk for early transplant-related complications.

Tailored strategy for AML patients receiving allogeneic peripheral blood stem cell transplantation

Considering the heterogeneity of acute myelogenous leukemia (AML), along with the pros and cons of allogeneic peripheral blood stem cell transplantation (PBSCT), a tailored strategy is needed to minimize the transplant-related mortality and maximize the transplant outcomes in AML patients exhibiting certain factors that have an impact on the post-transplant quality of life and outcomes. The factors that need to be considered when tailoring a strategy in an allogeneic PBSCT setting include the recipient's performance status and co-morbid disease include AML risk stratification, disease status, expected severity of graft-versus-host disease, and the necessity of a graft-versus-leukemia effect. Accordingly, this review article describes a possible tailoring strategy for AML patients receiving allogeneic PBSCT based on certain factors influencing the transplant outcome.

Conditioning including antithymocyte globulin followed by unmanipulated HLA-mismatched/haploidentical blood and marrow transplantation can achieve comparable outcomes with HLA-identical sibling transplantation

The outcomes of 293 patients with leukemia undergoing HLA-identical sibling (n = 158) or related HLA-mismatched (n = 135) hematopoietic cell transplantation (HCT) performed during the same time period were compared. Patients received BUCY2 in HLA-identical sibling HCT or BUCY2 + ATG in mismatched HCT as conditioning regimens, followed by unmanipulated marrow and/or peripheral blood (PB) transplantation. All patients achieved full engraftment. The cumulative incidences of grades II to IV acute graft-versus-host disease (aGVHD) in the matched and mismatched cohorts were 32% (CI, 25%-39%) versus 40% (CI, 32%-48%, P = .13), respectively, with the relative risk (RR) = 0.64 (95% CI, 0.43-0.94), P = .02. The incidence of chronic GVHD did not differ significantly between the cohorts (P = .97). Two-year incidences of treatment-related mortality and relapse for matched versus mismatched were 14% (range, 9%-20%) versus 22% (range, 15%-29%) with P = .10 and 13% (range, 8%-19%) versus 18% (range, 10%-27%) with P = .40, respectively. Two-year adjusted leukemia-free survival (LFS) and overall survival were 71% (range, 63%-78%) versus 64% (range, 54%-73%) with P = .27 and 72% (range, 64%-79%) versus 71% (range, 62%-77%) with P = .72, respectively. Multivariate analyses showed that only advanced disease stage and a diagnosis of acute leukemia had increased risk of relapse, treatment failure, and overall mortality. In summary, HCT performed with related HLA-mismatched donors is a feasible approach with acceptable outcomes.

Donor cytomegalovirus seropositivity and the risk of leukemic relapse after reduced-intensity transplants

OBJECTIVES

Despite effective preemptive and prophylactic therapeutic strategies, cytomegalovirus (CMV) seropositivity of either recipient and/or donor still remains an important parameter for outcome even after reduced-intensity allogeneic stem cell transplantation (SCT). Whether CMV seropositivity of the donor might have an impact on leukemic relapse is unknown.

PATIENTS

Between June 1999 and February 2004 48 patients ineligible for conventional allotransplantation underwent reduced-intensity transplants at our institution. Twenty-seven (56%) patients had a CMV-seropositive donor.

RESULTS

While donor CMV seropositivity had no effect on overall survival, having a CMV-seropositive donor was associated with a significantly lower risk for relapse (20% vs. 52%, P = 0.02). The beneficial effect of a CMV-seropositive donor, however, was offset by a higher transplant-related mortality (42% vs. 19% in patients with a CMV-seronegative donor, P = 0.2). Donor CMV serostatus had no effect on the incidence of CMV infection/disease, and acute or chronic graft-vs.-host disease. Overall, 27 patients died during the observation period. Causes of death in patients with a CMV-seropositive donor were primarily transplant-related (11 vs. 4 in patients with CMV-seronegative donors), whereas leukemic relapse was the leading cause of death in patients with a CMV-seronegative donor (8 vs. 4 in patients with a CMV-seropositive donor, P = 0.038, chi-squared test). Multivariate Cox regression analysis showed risk category by the underlying disease and donor CMV seropositivity to be significant predictors of leukemic relapse following reduced-intensity transplants.

CONCLUSIONS

These preliminary results suggest a possible role of donor CMV serostatus on the risk of relapse following reduced-intensity allogeneic SCT.

Antithymocyte globulin pharmacokinetics in pediatric patients after hematopoietic stem cell transplantation

To analyze the dose effects of rabbit-derived antithymocyte globulin (ATG) in children after allogeneic hematopoietic stem cell transplantation (HSCT), ATG serum levels were monitored in 32 children and adolescents (median age 3.42 years, range 0.34-18.67 years) and the incidence of acute and chronic graft-versus-host disease, rejection, viral infections, EBV-lymphoproliferative disease, and survival was correlated with the ATG dose used. Cumulative doses from 7.5 to 20 mg/kg showed a constant half-life and linear correlation between dose and Cmax, whereas higher doses (30-40 mg/kg) accumulated in the body. High-dose ATG is of no benefit for preventing graft-versus-host disease but is associated with a significant increase in EBV-linked disease, and it appears to enhance the susceptibility to fatal viral infections and rejection. These data strongly support the use of a low-dose ATG regimen in pediatric HSCT.

Bleeding complications after hematopoietic stem cell transplantation

Hemostatic disturbances are common in patients undergoing hematopoietic stem cell transplantation (HSCT), and have a significant impact on morbidity and mortality. Graft-versus-host disease (GvHD), in which the donor's T lymphocytes mount an immune response against the recipient's cells, is a life-threatening condition that correlates strongly with the incidence and severity of bleeding episodes, highlighting the complex interaction between the hemostatic and immunological systems. Patients with GvHD of the gut also exhibit a deficiency of factor XIII (FXIII), further increasing the hemorrhagic risk. Among other risk factors for bleeding complications is use of the purified polyclonal immunoglobulin G (IgG), antithymocyte globulin (ATG). Although frequently used in preparative conditioning regimens, ATG may contribute to leukopenia, platelet reduction, and signs of disseminated intravascular coagulation (DIC). This paper will examine the cause and incidence of bleeding complications in patients undergoing HSCT, the potential contribution of GvHD and ATG to such bleeds, and the close interaction between the hemostatic and immune systems. The role of recombinant FVIIa as a hemostatic agent for the treatment of HSCT-associated hemorrhage will be briefly explored.

Phenotype, function and chimaerism of monocyte-derived blood dendritic cells after allogeneic haematopoietic stem cell transplantation

Dendritic cells (DCs) are essential for initiating T-cell responses against either host- or leukaemia-specific antigens. We analysed phenotype, allostimulatory capacity and chimaerism of monocyte-derived DCs (moDCs) serially in 28 patients receiving allogeneic stem cell grafts after conventional myeloablative (n = 14) or reduced-intensity conditioning (RIC, n = 14). Although the recovery of phenotype and function of moDCs after myeloablative stem cell transplantation (SCT) was prompt, there was a trend to a lower expression of co-stimulatory molecules and major histocompatibility antigen class II antigens on mature moDCs in patients who had received RIC transplants. Similarly, the allostimulatory capacity of mature moDCs after RIC transplants was reduced for up to 6 months. Six out of 14 (43%) RIC transplant patients showed a pattern of mixed chimaerism within the first 3 months after transplant. RIC transplant patients with a mixed donor DC chimaerism had a significantly higher risk of relapse (75% versus 35% for patients with full donor DC chimaerism, P = 0.03) but a lower incidence of acute graft-versus-host disease (25% versus 56% for patients with full donor DC chimaerism, P = 0.157). These data, although preliminary, provide evidence that DC function is impaired after RIC transplants and that DC chimaerism may have an impact on graft-versus-host and graft-versus-leukaemia reactions.