Improved outcome of alternative donor bone marrow transplantation in children with severe aplastic anaemia using a conditioning regimen containing low-dose total body irradiation, cyclophosphamide and Campath

Successful preemptive therapy with single-dose rituximab for Epstein-Barr virus infection to prevent post-transplant lymphoproliferative disease after pediatric hematopoietic stem cell transplantation

BACKGROUND

The efficacy of preemptive treatment containing rituximab to prevent post-transplant lymphoproliferative disease (PTLD) in children has not yet been fully elucidated.

METHODS

We analyzed 19 pediatric patients who developed high Epstein-Barr virus (EBV) DNAemia (EBV viral load of greater than 40 000 copies/mL) after allogeneic hematopoietic stem cell transplantation (HSCT) and were preemptively administered rituximab. Rituximab was intravenously injected at a dose of 375 mg/m² once the EBV viral load was greater than 40 000 copies/mL.

RESULTS

In all 19 patients, EBV DNAemia was eradicated after a median of 9 days (range, 3-20 days), and PTLD did not occur. One patient had transient fever, and four patients did not fully recover B cell counts after transplantation. We suggested that delayed B cell recovery was caused by chronic graft-versus-host disease (GVHD) related drugs, not rituximab administration. And there were no other infection-related side effects.

CONCLUSIONS

In conclusion, preemptive therapy containing rituximab is expected to reduce the incidence of PTLD after HSCT and improve post-transplantation outcomes in children.

Updated Guidelines for the Treatment of Acquired Aplastic Anemia in Children

PURPOSE OF REVIEW

This review aimed to provide updated guidelines for the management of children with acquired aplastic anemia (AA), particularly focusing on hematopoietic stem cell transplantation (HSCT).

RECENT FINDINGS

Failure-free survival for children with aplastic anemia has been shown to be better after bone marrow transplantation (BMT) from matched or one-locus mismatched related donors (MRD/1MMRD) than after immunosuppressive therapy (IST). A combination of the absence of minor paroxysmal nocturnal hemoglobinuria clones and short telomere length was identified as a strong predictor of a poor response to IST. Upfront HSCT from matched unrelated donors (MUD) and MRD was recently demonstrated to have comparable outcomes. Moreover, unrelated cord blood transplantation (UCBT) and haploidentical HSCT have shown promising outcomes, and the fludarabine/melphalan-based regimen has resulted in excellent survival without poor graft function. BMT from MRD/1MMRD is the treatment of choice. When a MRD/1MMRD is not available, upfront BMT from a MUD should be considered for patients with only a slim chance of responding to IST. UCBT and haploidentical HSCT are promising options. This updated treatment algorithm should improve overall outcomes for children with AA.

Alemtuzumab based reduced intensity transplantation for pediatric severe aplastic anemia

BACKGROUND

Hematopoietic cell transplantation (HCT) is curative in patients with severe aplastic anemia (SAA). HCT is considered at presentation when a HLA-matched related donor (MRD) is available and has a high success rate. Unrelated donor (URD) transplants are typically undertaken if immunosuppressive therapy fails. Increased toxicity and graft rejection are often encountered in this setting.

PROCEDURE

We report a prospective multi-center trial of HCT in 17 children with SAA following novel reduced intensity conditioning with alemtuzumab, fludarabine and melphalan, and the best available donor. Nine were URD transplants matched at 7-8/8 loci, and performed following failure of immune suppression. Median follow up was 61 months (range 6-128).

RESULTS

All patients engrafted. Estimated 5 year event-free and overall-survival was 88% (95%CI 65.7-96.7). Five year overall survival for MRD and URD transplants was 100% and 78% (95%CI 45-93.6) respectively. Median times to neutrophil and platelet engraftment was 14 (range 10-27) and 23.5 (range 11-65) days respectively. Treatment related mortality was 12%. The incidence of grade II-IV and III-IV acute graft-versus-host disease was 29% and 18% respectively. At two years, all but one patient discontinued immunosuppression successfully. Laboratory measures of immune reconstitution normalized at one year and infection rates were low in the latter part of the first year.

CONCLUSIONS

HCT using this RIC approach was well tolerated and successful in achieving donor engraftment and early immune reconstitution with good quality of life free of immune suppression. Children with SAA can be successfully transplanted using alemtuzumab based conditioning.

The diagnosis and treatment of aplastic anemia: a review

Aplastic anemia is a rare disorder characterized by suppression of bone marrow function resulting in progressive pancytopenia. A trigger-related abnormal T cell response facilitated by some genetic predisposition has been postulated as the pathogenetic mechanism leading to the overproduction of bone marrow-inhibiting cytokines. Immuno-mediated pathogenesis is confirmed by the response to immunosuppressive treatment (IST) (cyclosporin A+ATG), which represents the first-choice therapy for patients <40 years when a matched sibling donor (MSD) is not available for transplant. MSD hematopoietic stem cell transplantation (HSCT) is associated with cure in ~90 % of patients. IST up-front provides an overall survival (OS) rate of above 90 %, but a response rate of about 60 %. Front-line matched unrelated donor (MUD) appears to be a viable option in children with similar OS and event-free survival to that in MSD HSCT. MUD HSCT post-IST failure proved to be a very good rescue strategy. Haploidentical donors/cord blood transplants or alternative immunosuppressive therapies, such as alemtuzumab, may represent valid tools for resistant/relapsing cases. New promising strategies, such as eltrombopag, are now under investigation. Patients should be offered an accurate diagnostic work-up in order to rule out other underlying disorders, primarily constitutional marrow failures, which may require different approaches.

Hematopoietic Cell Transplantation Using Reduced-Intensity Conditioning Is Successful in Children with Hematologic Cytopenias of Genetic Origin

Genetically derived hematologic cytopenias are a rare heterogeneous group of disorders. Allogeneic hematopoietic cell transplantation (HCT) is curative but offset by organ toxicities from the preparative regimen, graft rejection, graft-versus-host disease (GVHD), or mortality. Because of these possibilities, consideration of HCT can be delayed, especially in the unrelated donor setting. We report a prospective multicenter trial of reduced-intensity conditioning (RIC) with alemtuzumab, fludarabine, and melphalan and HCT in 11 children with marrow failure of genetic origin (excluding Fanconi anemia) using the best available donor source (82% from unrelated donors). The median age at transplantation was 23 months (range, 2 months to 14 years). The median times to neutrophil (>500 × 10(6)/L) and platelet (>50 × 10(9)/L) engraftment were 13 (range, 12 to 24) and 30 (range, 7 to 55) days, respectively. The day +100 probability of grade II to IV acute GVHD and the 1-year probability of limited and extensive GVHD were 9% and 27%, respectively. The probability of 5-year overall and event-free survival was 82%; 9 patients were alive with normal blood counts at last follow-up and all were successfully off systemic immunosuppression. In patients with genetically derived severe hematologic cytopenias, allogeneic HCT with this RIC regimen was successful in achieving a cure. This experience supports consideration of HCT early in such patients even in the absence of suitable related donors.

Deletion of Fanca or Fancd2 dysregulates Treg in mice

Fanconi anemia (FA) is a genetic disorder associated with bone marrow (BM) failure and leukemia. Recent studies demonstrate variable immune defects in FA. However, the cause for FA immunodeficiency is unknown. Here we report that deletion of Fanca or Fancd2 dysregulates the suppressive activity of regulatory T cells (Tregs), shown functionally as exacerbation of graft-vs-host disease (GVHD) in mice. Recipient mice of Fanca(-/-) or Fancd2(-/-) BM chimeras exhibited severe acute GVHD after allogeneic BM transplantation (BMT). T cells from Fanca(-/-) or Fancd2(-/-) mice induced higher GVHD lethality than those from wild-type (WT) littermates. FA Tregs possessed lower proliferative suppression potential compared with WT Tregs, as demonstrated by in vitro proliferation assay and BMT. Analysis of CD25(+)Foxp3(+) Tregs indicated that loss of Fanca or Fancd2 dysregulated Foxp3 target gene expression. Additionally, CD25(+)Foxp3(+) Tregs of Fanca(-/-) or Fancd2(-/-) mice were less efficient in suppressing the production of GVHD-associated inflammatory cytokines. Consistently, aberrant NF-κB activity was observed in infiltrated T cells from FA GVHD mice. Conditional deletion of p65 in FA Tregs decreased GVHD mortality. Our study uncovers an essential role for FA proteins in maintaining Treg homeostasis, possibly explaining, at least in part, the immune deficiency reported in some FA patients.

Allogeneic stem cell transplantation for children with acquired severe aplastic anaemia: a retrospective study by the Viva-Asia Blood and Marrow Transplantation Group

We retrospectively analysed the outcomes of 127 children with acquired severe aplastic anaemia (SAA) who had received haematopoietic stem cell transplantation (HSCT) between 2000 and 2011 in one of the 10 Asia Pacific institutions. Fifty-three were matched sibling donor (MSD) and 74 were alternative donor (AD), including 22 matched unrelated donor, 32 mismatched unrelated donor and 20 mismatched related donor. With a median follow up 45.5 months (13-139) and when compared to the MSD group, AD recipients had more grade II-IV acute graft-versus-host disease (aGVHD; 14.3% vs. 32.8%, P = 0.029), but similar grade III-IV aGVHD (10.2% vs. 12.5%, P = 0.774), graft failure (GF) (15.1% vs. 15.5%, P = 0.658) and 5-year overall survival (90.6% vs. 83.7%, P = 0.251). As a source of stem cell, peripheral blood stem cells (PBSC) resulted in less GF (18% vs. 9.1% P = 0.013), similar grade II-IV aGVHD (28.1% vs. 17.4%, P = 0.258), chronic GVHD (25.8% vs. 29.3%, P = 0.822) and similar outcomes (89.7% vs. 82.4%, P =0.665) when compared to bone marrow (BM). In univariate analysis, GF (P < 0.001) and grade II-IV aGVHD (P = 0.009) were predictors of poor survival. In multivariate analysis, only GF was associated with poor survival (P = 0.012). The outcome of AD and PBSC HSCT were comparable to that of MSD and BM HSCT in the Asia Pacific region.

Haploidentical transplantation in patients with acquired aplastic anemia

Haploidentical SCT (haplo-SCT) has been considered a therapeutic option in patients with acquired severe aplastic anemia (SAA) failing at least one course of immune suppressive therapy with antithymocyte globulin and lacking an HLA-matched related or unrelated donor. The platforms of both ex vivo T-cell-depleted and unmanipulated grafts have been explored in children and adults. Overall, the primary objective of a stable haploidentical hematopoietic engraftment with a low rate of GVHD is unmet in a significant proportion of patients undergoing haplo-SCT for SAA. Haploidentical transplants for refractory SAA should be performed in a specialist center with major experience in hematopoietic SCT procedures and preferably performed within the framework of a local clinical protocol designed specifically to address the prevention of graft rejection and GVHD.

A novel protocol for haploidentical hematopoietic SCT without in vitro T-cell depletion in the treatment of severe acquired aplastic anemia

Mismatched related donors of hematopoietic SCT (HSCT) for severe aplastic anemia (SAA) present challenges mainly associated with graft failure and GVHD. The greater the HLA disparity, the poorer the OS. About 19 consecutive SAA/very SAA (VSAA) patients who received HSCT from haploidentical family donors in our center are reported in this study, 18/19 pairs had 2-3 loci mismatched. All 19 cases failed to respond to previous therapy and were heavily transfused before transplantation. The conditioning regimen before HSCT included BU, CY and thymoglobulin. The recipients received CsA, mycophenolate mofetil (MMF) and short-term MTX for GVHD prophylaxis. The source of stem cell grafts was a combination of G-CSF-primed BM and G-CSF-mobilized peripheral blood stem cells. All patients achieved 100% donor myeloid engraftment; the median time for myeloid engraftment was 12 days (ranging from 10-29 days) and for platelets was 18 days (ranging from 8-180 days) with a cumulative platelet engraftment incidence of 84.21 ± 10.53%. The cumulative incidence was 42.1 ± 11.3% for grade II-IV acute GVHD and 56.2 ± 12.4% for chronic GVHD. The OS was 64.6 ± 12.4% with a median 746-day (90-1970) follow-up for surviving patients. These limited retrospective analysis data suggest that HLA-haploidentical HSCT for SAA patients without an HLA-identical sibling donor might be feasible. Further research to increase OS by decreasing GVHD while maintaining stable engraftment will be needed in the future.

Busulfan, fludarabine, and alemtuzumab as a reduced toxicity regimen for children with malignant and nonmalignant diseases improves engraftment and graft-versus-host disease without delaying immune reconstitution

For children receiving allogeneic hematopoietic stem cell transplants (HSCTs), the toxicity of the conditioning regimen and graft failure remain challenges. We previously reported that targeted i.v. busulfan, fludarabine, and rabbit anti-thymocyte globulin (rATG) decreased toxicity but had a graft failure rate of 21%. To improve the engraftment rate, we replaced ATG with alemtuzumab, a monoclonal Ab targeting CD52. Thirty-five children with malignant and nonmalignant diseases were enrolled in this phase II prospective study. Twelve children had HLA-matched related donors (MRDs), 16 had 10 of 10, and 7 had 9 of 10 HLA allele-matched unrelated donors (MUDs). Thirty-one of 34 evaluable patients (91%) achieved a durable engraftment. All 3 patients who rejected had a nonmalignant disease and received a MUD transplantation (2 mismatched at 1 antigen). Three patients died of a transplantation-related complication (9% ± 5.2%). Seven patients had disease relapse or progression, 2 of whom died. At a median follow-up of 35 months (range, 15-85 months), the event-free survival (EFS) was 61% ± 9.0% and the overall survival (OS) was 78% ± 7.5%. The median time to neutrophil recovery, B cell, and T cell reconstitution were 16 days, 3 months, and 6 months, respectively. At 1 year, the median donor chimerism in whole blood, CD3, CD14/15, and CD19 subsets were 97%, 87%, 100%, and 99%, respectively. Six patients (17% ± 6.6%) developed acute graft-versus-host disease (aGVHD), only 2 of which were >grade II. Two patients (8% ± 5.4%) progressed to chronic GVHD (cGVHD). These results suggest that replacement of rATG with alemtuzumab may improve engraftment as well as decrease cGVHD rates without resulting in delays in immune reconstitution.

Excellent outcome of matched unrelated donor transplantation in paediatric aplastic anaemia following failure with immunosuppressive therapy: a United Kingdom multicentre retrospective experience

We retrospectively analysed the outcome of consecutive children with idiopathic severe aplastic anaemia in the United Kingdom who received immunosuppressive therapy (IST) or matched unrelated donor (MUD) haematopoietic stem cell transplantation (HSCT). The 6-month cumulative response rate following rabbit antithymocyte globulin (ATG)/ciclosporin (IST) was 32·5% (95% CI 19·3-46·6) (n = 43). The 5-year estimated failure-free survival (FFS) following IST was 13·3% (95% confidence interval [CI] 4·0-27·8). In contrast, in 44 successive children who received a 10-antigen (HLA-A, -B, -C, -DRB1, -DQB1) MUD HSCT there was an excellent estimated 5-year FFS of 95·01% (95% CI 81·38-98·74). Forty of these children had failed IST previously. HSCT conditioning was a fludarabine, cyclophosphamide and alemtuzumab (FCC) regimen and did not include radiotherapy. There were no cases of graft failure. Median donor chimerism was 100% (range 88-100%). A conditioning regimen, such as FCC that avoids total body irradiation is ideally suited in children. Our data suggest that MUD HSCT following IST failure offers an excellent outcome and furthermore, if a suitable MUD can be found quickly, MUD HSCT may be a reasonable alternative to IST.

Is it time for a change? The case for early application of unrelated allo-SCT for severe aplastic anemia

Severe aplastic anemia (SAA) is a BM failure syndrome in which allo-SCT remains a highly effective curative option. Its application remains limited by donor availability and by the potential for treatment-related morbidity and mortality. The improved outcomes with unrelated transplantation are a result of the advent of molecular donor-recipient matching, generation of effective novel conditioning regimens, improvement of supportive care and expansion of the donor registry. Decision making regarding the earlier use of unrelated transplant procedures is rapidly evolving. This paper reviews critical data relevant to these treatment options and recommends early consideration of related SCT for patients with SAA who show failure of immune suppressive therapy.

Comparison of matched-sibling donor BMT and unrelated donor BMT in children and adolescent with acquired severe aplastic anemia

From January 1991 to March 2007, 61 children and adolescent with acquired severe aplastic anemia received BMT in our institutions. We retrospectively compared the outcome of 30 cases of matched-sibling donor BMT (MSD-BMT) and 31 cases of unrelated donor BMT (URD-BMT). We observed one graft failure among MSD-BMT recipients and three graft failures among URD-BMT recipients, respectively. No patients in the MSD-BMT group developed grades II-IV acute GVHD compared with 11 of 30 patients (37%) in the URD-BMT group (P<0.001). One of 30 MSD-BMT recipients (3%) developed chronic GVHD compared with 8 of 30 URD-BMT recipients (27%) (P=0.013). The incidence of EBV and CMV reactivation was 11 of 20 URD-BMT recipients and 23 of 30, respectively. One patient in the URD-BMT group died of a motor accident 5.5 years after BMT. Ten-year OS was 100% in MSD-BMT recipients and 93.8% (95% CI, 81.9-100%) in URD-BMT recipients, respectively (P=0.252). Ten-year failure-free survival was 96.7% (95% CI, 90.2-100%) in the MSD-BMT group and 84.7% (95% CI, 70.2-99.2%) in the URD-BMT group, respectively (P=0.161).

Tacrolimus/Methotrexate versus cyclosporine/methotrexate as graft-versus-host disease prophylaxis in patients with severe aplastic anemia who received bone marrow transplantation from unrelated donors: results of matched pair analysis

Tacrolimus (FK) and cyclosporine (CsA) have been shown to be effective in the prophylaxis of graft-versus-host disease (GVHD). However, no comparative studies have yet been conducted to examine the efficacy of FK/methotrexate (MTX) and CsA/MTX in patients with severe aplastic anemia (SAA) given unrelated donor bone marrow transplantation (U-BMT). We used matched-pair analysis to compare FK/MTX with CsA/MTX in patients with SAA who received U-BMT through the Japan Marrow Donor Program. Forty-seven pairs could be matched exactly for recipient age and conditioning regimens. Forty-five patients achieved engraftment in the FK group and 42 patients in the CsA group. The probability of grade II-IV acute GVHD (aGVHD) was 28.9% in the FK group and 32.6% in the CsA group (P=.558). The probability of chronic GVHD (cGVHD) was 13.3% in the FK group and 36.0% in the CsA group (P=.104). The 5-year survival rate was 82.8% in the FK group and 49.5% in the CsA group (P=.012). The study shows the superiority of FK/MTX over CsA/MTX in overall survival because of the lower incidence of transplantation-related deaths. A prospective randomized study comparing FK/MTX and CsA/MTX is warranted.

Allogeneic haemopoietic stem cell transplantation in children: what alternative donor should we choose when no matched sibling is available?

Allogeneic haemopoietic stem cell transplantation has provided curative therapy for life-threatening malignant and non-malignant diseases in children for over 40 years. Only 25% of children in whom an allograft is indicated have the ideal option of a human leucocyte antigen-identical sibling donor. Substantial advances in the use of alternative donors (unrelated volunteer donors, haploidentical family donors and unrelated umbilical cord blood donors) now make it possible for almost all children to benefit from this life-saving treatment. Each donor choice is associated with distinct advantages and disadvantages, which have greater or lesser importance in different diseases. We review the current status of alternative donor transplantation for haematological malignancies, primary immunodeficiencies, inherited metabolic disorders and bone marrow failure syndromes and outline the current UK consensus donor selection algorithms for these disease groups.

Hematopoietic stem cell transplantation for bone marrow failure syndromes in children

Bone marrow failure (BMF) syndromes include a broad group of diseases of varying etiologies, in which hematopoeisis is abnormal or completely arrested in one or more cell lines. BMF can be an acquired aplastic anemia (AA) or can be congenital, as part of such syndromes as Fanconi anemia (FA), Diamond Blackfan anemia, and Schwachman Diamond syndrome (SDS). In this review, we first address the evolution and current status of bone marrow transplantation (BMT) in the pediatric population in the most common form of BMF, acquired AA. We then discuss pediatric BMT in some of the more common inherited BMF syndromes, with emphasis on FA, in which experience is greatest. It is important to consider the possibility of a congenital etiology in every child (and adult) with marrow failure, because identification of an associated syndrome provides insight into the likely natural history of the disease, as well as prognosis, treatment options for the patient and family, and long-term sequelae both of the disease itself and its treatment.

Acquired aplastic anemia in childhood

In comparison to past decades, children who have acquired aplastic anemia (AA) enjoy excellent overall survival that reflects improvements in supportive care, more accurate exclusion of children who have alternate diagnoses, and advances in transplantation and immunosuppressive therapy (IST). Matched sibling-donor hematopoietic stem cell transplants (HSCT) routinely provide long-term survival in the range of 90%, and 75% of patients respond to IST. In this latter group, the barriers to overall and complication-free survival include recurrence of AA, clonal evolution with transformation to myelodysplasia/acute myelogenous leukemia, and therapy-related toxicities. Improvements in predicting responses to IST, in alternative-donor HSCT, and in rationalizing therapy by understanding the pathophysiology in individual patients are likely to improve short- and long-term outcomes for these children.

Fludarabine based reduced intensity conditioning regimens in children undergoing allogeneic stem cell transplantation for severe aplastic anemia

Fourteen children with a median age of 9.8 yr with SAA (10 males, four females) underwent related HLA identical allogeneic stem cell transplantation using Flu, Cy +/- ATG between 2004 and 2006. GVHD prophylaxis consisted of cyclosporine +/- mini methotrexate. Graft source included PBSCs (seven) or BM (seven). One patient expired <7 days post-transplant, while 12 (85.7%) patients engrafted with median neutrophil and platelet engraftment times of 13.8 and 14.5 days each. One patient had primary graft failure and expired on Day +27. Acute GVHD was seen in 25% of evaluable patients while limited chronic GVHD was seen in 33%. At a mean follow-up of 18 months, 12 patients (85.7%) are alive and well. Compared with a historical cohort of 12 children transplanted using Cy/ATG, there was faster engraftment (13.8 vs. 16.4 days; p = 0.002) with lower rejection rates (7.1 vs. 36.3%; p = 0.133) and improved event free (85.7 vs. 54.5%; p = 0.177) and overall survival (85.7 vs. 63.6%; p = 0.350). Flu with Cy +/- ATG reduces rejection and improves overall and event free survival in children with aplastic anemia.

An update on the management of severe idiopathic aplastic anaemia in children

The current outlook for a child with severe idiopathic aplastic anaemia (AA) is very much better than in previous decades. In part, this may reflect better differentiation of idiopathic and inherited marrow failure. For children with idiopathic AA and a human leucocyte antigen (HLA)-matched sibling donor (MSD), allogeneic haematopoietic stem-cell transplantation (AHSCT) is the primary therapy of choice, offering long-term disease-free survival of 90%, although graft-versus-host disease remains a cause of long-term morbidity. A greater treatment challenge remains for those children without a MSD. Combination immunosuppressive therapy (IST) is associated with response rates of 70% or more. However, relapse and clonal evolution with transformation to myelodysplasia or acute myeloid leukaemia remain significant problems after IST and long-term event-free survival rates are less impressive. For children who do not have a sustained response to IST, alternate donor AHSCT should be considered. New HLA typing technologies, novel stem cell sources, reduced-intensity conditioning and graft engineering have reduced toxicity and improved the outcome after alternate donor AHSCT. Emerging therapies that capitalise on recent advances in our understanding of the pathophysiology of idiopathic AA and the immunobiology of AHSCT and IST may further improve the long-term outcome of this disease.

Bone marrow transplantation in children with severe aplastic anemia using a conditioning regimen containing 3 Gy of total body irradiation, cyclophosphamide with or without antithymocyte globulin

We have employed the 3 Gy total body irradiation (TBI) containing conditioning regimen to bone marrow transplantation (BMT) for severe aplastic anemia (SAA) in pediatric patients irrespective of donor type since March 1986. The outcome of BMT for 17 SAA patients is favorable. Eight patients received BMT from human leukocyte antigen matched-related donors (MRD) and nine received BMT from alternative donors. The conditioning regimen consisted of 3-Gy TBI and cyclophosphamide of 200 mg/kg in the BMT from MRD. In the case of BMT from alternative donor, antithymocyte globulin 10 mg/kg was added to the regimen. Fifteen of 17 patients (88%) engrafted on median of day 18 (range, 11-26) and all 13 evaluable patients showed complete donor chimerism by median 30 (range, 13-47) days after BMT. Fourteen patients have survived with a median follow-up of 67 (range, 2-228) months and the probability of survival was 81.9% (95% CI, 63.3-100%). No late complications including second malignancies caused by TBI have been observed and all three female patients have regular menstruation. In conclusion, TBI of 3 Gy appears to be an appropriate dose regarding to ensure engraftment and avoid the risk of late adverse event for SAA patients.

Comparable Outcomes of Matched-Related and Alternative Donor Stem Cell Transplantation for Pediatric Severe Aplastic Anemia

Matched sibling donor (MSD) bone marrow transplantation is the treatment of choice for pediatric patients with severe aplastic anemia (SAA); however, only about 33% of patients will have an HLA-identical sibling. Alternative donor (AD) transplants may be an option for these patients, but such therapies have been associated with greater incidence of graft failure and graft-versus-host disease (GVHD). We retrospectively analyzed 36 pediatric patients who received 38 bone marrow or peripheral blood stem cell transplants (15 MSD and 23 AD) for SAA at our institution from April 1997 to October 2005. Nineteen AD recipients received reduced intensity conditioning with cyclophosphamide, low-dose total body irradiation, and antithymocyte globulin (ATG) or Campath. The 4-year overall survival for MSD recipients was 93% versus 89% for AD recipients treated with reduced intensity conditioning regimens at a median follow-up of 52 months (range, 6-99 months). No patient receiving Campath, compared with 3 of 9 patients receiving ATG, developed extensive, chronic GVHD. We conclude that, for children with SAA, AD transplantation is as effective as MSD transplantation. Further, compared with ATG, preparatory regimens containing Campath may be associated with a lower incidence of extensive, chronic GHVD.

Current concepts in the pathophysiology and treatment of aplastic anemia

Aplastic anemia, an unusual hematologic disease, is the paradigm of the human bone marrow failure syndromes. Almost universally fatal just a few decades ago, aplastic anemia can now be cured or ameliorated by stem-cell transplantation or immunosuppressive drug therapy. The pathophysiology is immune mediated in most cases, with activated type 1 cytotoxic T cells implicated. The molecular basis of the aberrant immune response and deficiencies in hematopoietic cells is now being defined genetically; examples are telomere repair gene mutations in the target cells and dysregulated T-cell activation pathways. Immunosuppression with antithymocyte globulins and cyclosporine is effective at restoring blood-cell production in the majority of patients, but relapse and especially evolution of clonal hematologic diseases remain problematic. Allogeneic stem-cell transplant from histocompatible sibling donors is curative in the great majority of young patients with severe aplastic anemia; the major challenges are extending the benefits of transplantation to patients who are older or who lack family donors. Recent results with alternative sources of stem cells and a variety of conditioning regimens to achieve their engraftment have been promising, with survival in small pediatric case series rivaling conventional transplantation results.

Retreatment with rabbit anti-thymocyte globulin and ciclosporin for patients with relapsed or refractory severe aplastic anaemia

The management of patients with severe aplastic anaemia (SAA) who do not have a matched sibling donor and fail a course of horse anti-thymocyte globulin (h-ATG)/ciclosporin (CsA) is uncertain. Repeated courses of ATG-based immunosuppression are often employed; in children and increasingly in adults, alternative donor haematopoietic stem cell transplantation is an option. We analysed the success rate of retreatment with rabbit ATG (r-ATG)/CsA in 43 patients treated at our institution in the last 5 years; 22 were refractory (20 adults; two children) to h-ATG/CsA-based regimens and 21 (17 adults; four children) had relapsed after h-ATG/CsA-based regimens. The overall response rate was 30% in patients who were refractory to h-ATG and 65% in patients who had relapsed following h-ATG. The 1000-d survival in patients who responded to r-ATG was 90% compared with 65% in non-responders. Six patients developed a clonal haematological disorder; two were responders, two were non-responders and in two the evolution occurred before the response could be assessed at 3 months following r-ATG. Thirteen patients died; three were responders, six were non-responders and four patients died prior to 3 months when response was assessed. In our study, the response rate in refractory patients was inferior to what has been previously reported.

Overcoming graft rejection in heavily transfused and allo-immunised patients with bone marrow failure syndromes using fludarabine-based haematopoietic cell transplantation

Allogeneic haematopoietic cell transplantation (HCT) can cure a variety of non-malignant haematological disorders. Although transplant outcomes for selected patients with severe aplastic anaemia (SAA) and paroxysmal nocturnal haemoglobinuria (PNH) have improved, older age, allo-immunisation from transfusions, prior immunosuppressive therapy and a prolonged time from diagnosis to transplantation are associated with worse outcome. Because of its potent immunosuppressive effects, we investigated a fludarabine-based non-myeloablative conditioning regimen in patients with transfusion-dependent non-malignant haematological disorders at increased risk for graft rejection with conventional transplant conditioning. Twenty-six patients with transfusion dependent/anti-thymocyte globulin (ATG)-refractory SAA, PNH or pure red cell aplasia underwent HCT from a human leucocyte antigen (HLA)-compatible relative. Transplant conditioning consisted of cyclophosphamide (120 mg/kg) and fludarabine (125 mg/m2) with or without ATG. Ciclosporine, alone or combined with mycophenolate mofetil or methotrexate, was used as graft-versus-host disease (GVHD) prophylaxis. All patients achieved durable engraftment and transfusion-independence. Twenty-four of 26 patients are alive at a median of 21 months following transplantation. Although a high cumulative incidence of acute (65% grades II-IV, 54% grades III-IV) and chronic GVHD (56%) was observed, only one patient died from transplant-related causes (cumulative incidence 7%). These data show that HCT following fludarabine-based non-myeloablative conditioning results in durable engraftment and excellent survival in SAA and PNH patients at high risk for graft rejection.

Haematopoietic stem cell transplantation to treat aplastic anaemia

Aplastic anaemia (AA) consists of pancytopenia and empty bone marrow. Its incidence varies worldwide but predominates in developing countries. Diverse aetiologies are involved, with autoimmunity at the centre of the picture. For the 70% of patients with the severe and very severe forms of AA and who lack a human leukocyte antigen (HLA)-matched sibling, immunosuppressive therapy (IST) is key in treating the disease, with a remission rate close to 70%, an 80-90% 5-year survival rate in responding patients and a relapse rate close to 10%. For the 30% with a sibling donor available, haematopoietic stem cell transplant (HSCT) from bone marrow or peripheral blood has up to a 90% chance of cure, with a 5-10% graft rejection/failure rate. Patients who fail IST (25-30%) and lack a sibling donor can benefit from CD34(+)-enriched, partially T cell-depleted unrelated stem cell transplants, with a general survival rate up to 37%, the newest source of stem cells for this modality being cord blood. Non-myeloablative, irradiation-free conditioning regimens offer appreciable benefits, and new immunosuppressive agents, such as fludarabine and alemtuzumab, have been incorporated with promising preliminary results. Graft-versus-host disease, graft failure and infections remain significant challenges in HSCT for which innovative treatment strategies are being developed at present.

Diagnosis and treatment of children with aplastic anemia

BACKGROUND

Long-term survival rates among children diagnosed with severe aplastic anemia (SAA) are excellent due to the success of human leukocyte antigen (HLA)-identical related hematopoietic stem cell transplantation (HSCT), concurrent advances in immunosuppressive treatment (IST), and improved supportive care. The challenge in making treatment recommendations for children with SAA, therefore, is to balance the apparent chronicity and morbidity following IST, with the potential up-front toxicity and complications of HSCT.

METHODS

This review provides an update on the diagnosis and a risk-based treatment algorithm for children with acquired SAA. Recent experience using alternative donor HSCT and efforts to extend HSCT eligibility through advances in donor matching, de-escalation of conditioning regimens, and potential marrow graft engineering are highlighted. We discuss IST response rates, risks of relapse, and complications including clonal evolution.

CONCLUSIONS

While good treatment options exist for a majority of children diagnosed with SAA, novel non-transplantation treatments for unresponsive and relapsed patients without suitable transplant donors are needed. Further improvements in outcome will ultimately require a more complete understanding of the pathophysiology of aplastic anemia (AA).

Non-total body irradiation containing preparative regimen in alternative donor bone marrow transplantation for severe aplastic anemia

Using non-total body irradiation (TBI) containing preparative regimens, 13 patients with severe aplastic anemia (SAA) were transplanted from an alternative donor in a single institute. In total, 12 donors were unrelated volunteers and one was an HLA one-locus mismatched sibling. Median time from diagnosis of SAA to bone marrow transplantation (BMT) was 10.1 months (range, 1.6-180.1). Nine patients had received immunosuppressive treatment with ATG before BMT, while four had not. Preparative regimens consisted of cyclophosphamide plus ATG in nine patients, cyclophosphamide plus fludarabine in two patients, and cyclophosphamide plus fludarabine plus ATG in two patients. All patients received non-T-cell depleted bone marrow from the donor. Cyclosporine plus methotrexate were given for GVHD prophylaxis. All patients engrafted on a median of day 21 (range, 15-27). Grade III-IV acute GVHD developed in three (23%) of 13 patients and extensive chronic GVHD in four (31%) of 12 evaluable patients. With a median follow-up duration of 1138 days (range, 118-1553), 10 patients are alive with durable engraftment showing 74.6% (95% confidence interval, 49.5-99.7%) of survival rate. Cause of the deaths was CNS bleeding in one and chronic GVHD in two. In conclusion, non-TBI containing preparative regimen could ensure durable engraftment in alternative donor BMT for SAA and showed promising results.

Reduced-intensity allogeneic hematopoietic stem cell transplantation for acute leukemias: ‘what is the best recipe?’

Reduced-intensity stem cell transplantation (RIST) has been shown to be a safe and useful alternative transplant method for patients including elderly and medically unfit patients. RIST conditioning regimens vary widely in the intensity of myeloablation, immunoablation, and antileukemia effects, and thus optimal regimen for each disease entity is yet to be determined. Most reports on RIST to date are small, single-institution experiences or retrospective studies with heterogeneous patient populations and primary diseases, complicating any direct comparison between studies. In acute myeloid leukemia (AML), moderate-intensity regimens may be effective, achieving 30-70% 1-year disease-free survival in various series, but minimal-intensity regimens are associated with high relapse rates. In acute lymphoblastic leukemia (ALL), not even moderate-intensity regimens are effective and most patients with advanced ALL relapse post transplant. Thus, the risk/benefit ratios of graft-versus-host disease/graft-versus-leukemia effect differ among diseases. Larger, prospective, multi-center clinical trials are needed to determine the best use of RIST in hematologic malignancies.

Management of acquired aplastic anaemia

Outcome of patients with aplastic anaemia (AA), whether treated with allogeneic BMT or immunosuppressive therapy has steadily increased over the last three decades. However, there is a difference in quality of outcome between these two therapeutic modalities. There is no plateau for survival after ATG as patients are at later risk of transformation to myelodysplasia (MDS) or acute myeloid leukaemia (AML), paroxysmal nocturnal haemoglobinuria and relapse of their aplasia. In contrast, AA patients are not at risk of these later complications if they have undergone successful bone marrow transplantation. Long term survival after HLA identical sibling BMT is 80-90%, but GVHD and graft rejection remain to be addressed. The results of unrelated donor BMT for AA have shown considerable improvement over the last five years. Difficulties remain for those patients who fail immunosuppressive therapy and in whom BMT is not possible, since alternative immunosuppressive agents have so far proven to be somewhat disappointing.

In Vivo Alemtuzumab Enables Haploidentical Human Leukocyte Antigen-Mismatched Hematopoietic Stem-Cell Transplantation Without Ex Vivo Graft Manipulation

BACKGROUND

Alemtuzumab, a humanized monoclonal antibody directed against human CD52, has a strong lympholytic effect. This study evaluates the safety of unmanipulated peripheral blood stem-cell transplantation from two or three loci-mismatched related donors using alemtuzumab in vivo.

METHODS

A total body irradiation-based regimen was used in young patients, whereas those 50 years or older received fludarabine-based conditioning. Alemtuzumab was added to these regimens by intravenous infusion at 0.2 mg/kg per day for 6 days (days -8 to -3).

RESULTS

We treated 12 patients with a median age of 49.5 years. Eight patients demonstrated active disease, and four patients demonstrated acute leukemia in high-risk remission. All achieved neutrophil engraftment a median of 17.5 days after transplantation with complete donor-type chimerism. The cumulative incidence of grades III to IV acute graft-versus-host disease was only 9%. Infection-related deaths were not observed. CD3+/CD4+ and CD3+/CD8+ T cells were strongly suppressed within 2 months after transplantation, but recovered on day 90. Relapse was observed in five of eight patients who underwent transplantation for active disease, whereas none of the three patients who underwent transplantation in first remission had a relapse.

CONCLUSIONS

We conclude that in vivo alemtuzumab enables haploidentical hematopoietic stem-cell transplantation without ex vivo graft manipulation.

Marrow transplants from matched unrelated donors for aplastic anaemia using alemtuzumab, fludarabine and cyclophosphamide based conditioning

Graft failure, regimen-related toxicity and graft-versus-host disease (GVHD) are the critical barriers to unrelated donor transplants for aplastic anaemia (AA). We investigated the use of a novel conditioning regimen consisting of alemtuzumab (humanized CD52 antibody), fludarabine and cyclophosphamide in seven patients with AA, who underwent bone marrow transplant procedure using matched unrelated donors. The aetiology of AA was acquired (n=3), Fanconi's (n=3) and congenital (n=1). Median age was 13 years (range 8-35). All the donors were fully matched for HLA class I and II antigens using high-resolution typing. All the patients engrafted at a median of 18 days (range 13-35). Two patients died of transplant-related complications: one of adenovirus disease and the other developed extensive chronic GVHD of skin followed by cytomegalovirus (CMV) disease. Three patients developed Grade II acute GVHD disease (GVHD); none had Grade III-IV acute GVHD. Of the six evaluable patients, only one developed chronic GVHD. We conclude that this conditioning regimen for unrelated donor transplants for AA is sufficiently immunosuppressive to allow stable engraftment and appears to have a favourable impact on the incidence and severity of GVHD, warranting further investigation.

Non-radiotherapy conditioning with stem cell transplantation from alternative donors in children with refractory severe aplastic anemia

Conditioning including total body/lymphoid irradiation is widely used to prevent graft rejection in patients with refractory severe aplastic anemia (SAA) undergoing hemopoietic cell transplantation (HCT) from alternative donors and or after graft manipulation. To reduce regimen-related toxicity we transplanted three children with refractory SAA after conditioning with radiotherapy-free regimens. Conditioning included fludarabine 175-180 mg/m2 in all patients. In addition, patient 1 (failing two previous grafts) received thiotepa 10 mg/kg and Campath-1H 60 mg/m2; patient 2 cyclophosphamide 120 mg/kg, thiotepa 15 mg/kg and OKT-3 0.1 mg/kg/day for 4 weeks; and patient 3 cyclophosphamide 120 and ATG 90 mg/kg. Stem cell source was unmanipulated marrow from the same unrelated donor as for the two previous transplantations in patient 1 and CD34+-purified peripheral blood stem cells from an HLA-matched unrelated donor and from the haploidentical mother in patients 2 and 3. Only patient 1 received graft-versus-host disease (GVHD) prophylaxis with cyclosporine A and mycophenolate mofetil. Follow-up is now 30, 51, and 15 months. None of the patients developed GVHD. All patients have normal counts with complete donor chimerism. Fludarabine-based conditioning is powerfully immunosuppressive and may be used for children with refractory SAA undergoing HCT from alternative donors even after rejection following previous HCT.

Unrelated donor bone marrow transplantation for children with severe aplastic anemia: minimal GVHD and durable engraftment with partial T cell depletion

Both increased graft rejection and increased graft vs host disease (GVHD) remain obstacles to success for unrelated donor (URD) BMT for patients with SAA. Partial T cell depletion (PTCD) may decrease the risk of severe GVHD, while still maintaining sufficient donor T lymphocytes to ensure engraftment. We report on 12 patients with SAA who underwent PTCD URD BMT. All patients had failed medical therapy or relapsed following initial responses, and were transfusion dependent. The median age was 6 years, and there were five males. Donors were matched for four patients, and mismatched for eight. All patients received total body irradiation with either Ara-C or thiotepa and cyclophosphamide. PTCD was accomplished using monoclonal antibody T10B9 or OKT3 and complement. All patients engrafted, with a median time of 18 days to ANC >500. Only one patient had greater than grade II acute GVHD; two patients had limited and one patient extensive chronic GVHD. Nine patients are alive and transfusion independent at a median months post BMT. Three patients died from infection or renal failure. This series suggests that an aggressive immunosuppressive conditioning regimen with PTCD results in successful engraftment and minimal GVHD in pediatric patients with SAA, even with HLA mismatched donors.

Fludarabine, cyclophosphamide plus thymoglobulin conditioning regimen for unrelated bone marrow transplantation in severe aplastic anemia

Antithymocyte globulin (ATG) has been used in severe aplastic anemia (SAA) as a part of the conditioning regimen. Among the many kinds of ATG preparations, thymoglobulin had been found to be more effective in preventing GVHD and rejection of organ transplants. As the fludarabine-based conditioning regimens without total body irradiation have been reported to be promising for bone marrow transplantation (BMT) from alternative donors in SAA, thymoglobulin was added to fludarabine and cyclophosphamide conditioning to reduce GVHD and to allow good engraftment in unrelated BMT. Five patients underwent BMT with cyclophosphamide (50 mg/kg once daily i.v. on days -9, -8, -7 and -6), fludarabine (30 mg/m2 once daily i.v. on days -5, -4, -3 and -2) and thymoglobulin (2.5 mg/kg once daily i.v. on days -3, -2 and -1) from HLA-matched unrelated donors. Complete donor type hematologic recovery was achieved in all patients. No serious complication occurred during BMT. Only one patient developed grade I acute GVHD resolved spontaneously. Except for one who had rupture of hepatic adenoma 78 days after BMT, all the other four patients are still alive with median 566 days. Fludarabine, cyclophosphamide plus thymoglobulin conditioning allows for the promising results of good engraftment, tolerable toxicity and minimal GVHD.

Successful Unrelated Cord Blood Transplantation Using a Reduced-Intensity Conditioning Regimen in a 6-Month-Old Infant with Congenital Neutropenia Complicated by Severe Pneumonia

Here we report the first successful unrelated cord blood transplantation (CBT) using reduced-intensity conditioning for the 'treatment of congenital neutropenia in a 6-month-old infant with complications of severe pneumonia probably due to Staphylococcus aureus infection. Because the patient showed no response to treatment with granulocyte colony-stimulating factor and had a cytogenetic aberration, unrelated CBT with an HLA-DRB1 genotypic mismatch was performed. The number of infused cells was 15 x 10(7)/kg. The preparative regimen was fludarabine, cyclophosphamide, and 6 Gy of total body irradiation. Teicoplanin was administered for bacterial pneumonia. Neutrophil engraftment was achieved on day 41 and was followed by clinical improvement. The patient gradually caught up on growth and development after the CBT. Unrelated CBT using a reduced-intensity conditioning regimen may be an effective treatment for congenital neutropenia.

Transplantation of highly purified CD34+ progenitor cells from alternative donors in children with refractory severe aplastic anaemia

Without transplantation from a human leucocyte antigen-identical family donor, refractory severe aplastic anaemia (SAA) has an unfavourable prognosis. Conventional transplantation from a matched unrelated donor carries a high rate of mortality. We transplanted large numbers of highly purified CD34+ cells from matched unrelated (n = 4), mismatched unrelated (n = 4) and mismatched related (n = 1) donors into nine children with refractory SAA. The grafts consisted of granulocyte colony-stimulating factor-mobilized peripheral positively selected CD34+ cells. A median of 15.1 x 106/kg CD34+ stem cells and 11 x 103/kg CD3+ T-lymphocytes were infused. No additional pharmacological graft versus host disease (GVHD) prophylaxis was given. At a median follow-up of 47 (range 37-72) months, eight patients (89%) were in complete remission with >90% donor chimaerism and no evidence of GVHD. One patient died on day +238 as a consequence of GVHD. The use of highly purified mobilized CD34+ stem cells warrants further clinical exploration in children with refractory SAA.

The role of haploidentical stem cell transplantation in the management of children with haematological disorders

The broader application of stem cell transplantation (SCT) for paediatric diseases has been limited by a lack of human leucocyte antigen (HLA)-matched donors. Virtually all children, however have at least one haploidentical parent who could serve as a donor. Such a donor is immediately available and the considerable costs of additional HLA typing, registry and banking expenditures that are necessary to procure an unrelated donor, could be reduced. Recent technological advances appear to have overcome the historical problems of graft rejection and severe graft versus host disease in the haploidentical setting, and in the latest studies the overall survival for children undergoing haploidentical SCT for leukaemia is now comparable with that following unrelated donor bone marrow or cord blood transplantation. Post-transplant infectious complications and leukaemia relapse remain the most important barriers yet to overcome, and new directions in the use of adoptive cellular immunity appear to be promising in this respect. Haploidentical SCT is now a viable option for those children who do not have an HLA compatible sibling or fully matched unrelated donor. The relative merits of a haploidentical family donor versus mismatched unrelated bone marrow or cord blood donation needs to be assessed in prospective, randomized clinical trials.

Immunosuppressive treatment of acquired aplastic anemia and immune-mediated bone marrow failure syndromes

Modern therapeutic strategies for the treatment of acquired aplastic anemia are based on the current understanding of its pathophysiology as well as empiric observations. Most cases of aplastic anemia appear to be the result of immune-mediated destruction of hematopoietic cells, which can be approached by stem cell transplantation in younger patients with appropriate histocompatible donors or by immunosuppression to reduce T-cell activity. Popular treatment regimens combine antithymocyte globulin with cyclosporine. Although a majority of patients respond with improved blood counts and achieve transfusion-independence, late clonal complications of myelodysplasia and cytogenetic abnormalities occur in a substantial minority of cases. Additionally, there is no clear algorithm for the treatment of refractory disease. Newer methods of treatment, including high-dose cyclophosphamide and the development of potentially tolerizing combinations of drugs. are under study. Effective therapies for aplastic anemia might also be applied to other T-cell mediated, organ-specific human diseases.

Stem cell transplantation for aplastic anemia

Survival of patients with aplastic anemia treated with transplantation of bone marrow has improved significantly over the past several decades. Allogeneic bone marrow transplantation (BMT) for patients with HLA-identical siblings is now the first-line therapy, and long-term survival of approximately 90% can be expected with cyclophosphamide/antithymocyte globulin conditioning and postgrafting methotrexate/cyclosporine immunosuppression. The outcome of unrelated donor BMT has also improved significantly with the identification of a preparative regimen with less toxicity combined with the development of high-resolution DNA-based HLA typing to identify the optimal unrelated marrow donor. Patients with fully HLA-matched unrelated donors should be considered candidates for transplantation prior to exposure to repeat courses of immunosuppression. Future progress in hematopoietic stem cell transplantation for aplastic anemia will be directed toward further decreasing the acute toxicity and decreasing the delayed effects of the conditioning regimens while maintaining highly reliable rates of sustained engraftment with prevention of acute and chronic graft-versus-host disease.