Long-term outcome of pediatric patients with severe aplastic anemia treated with antithymocyte globulin and cyclosporine

Current management of severe acquired aplastic anemia

Overall survival in severe aplastic anemia has markedly improved in the past four decades due to advances in stem cell transplantation, immunosuppressive therapies and supportive care. Horse anti-thymocyte globulin plus cyclosporine is the standard immunosuppressive regimen in severe aplastic anemia, and often employed as initial therapy as most are not candidates for a matched related stem cell transplantation. With this regimen, hematologic response can be achieved in 60 to 70% of cases, but relapse is observed in 30 to 40% of responders and clonal evolution in 10 to 15% of patients. Efforts to improve outcomes beyond horse anti-thymocyte globulin plus cyclosporine have been disappointing, with no significant improvement in the critical parameter of hematologic response, which strongly correlates with long-term survival in severe aplastic anemia. Furthermore, rates of relapse and clonal evolution have also not improved with the development of three drug regimens or with more lymphocytotoxic therapies. Therefore, horse anti-thymocyte globulin plus cyclosporine remains the standard immunosuppression of choice as first therapy in severe aplastic anemia. Interestingly, survival has markedly improved over the years in large part due to better anti-infective therapy and more successful salvage therapies with immunosuppression and stem cell transplantation. In this review general aspects of diagnosis and management are discussed.

Paroxysmal nocturnal hemoglobinuria and telomere length predicts response to immunosuppressive therapy in pediatric aplastic anemia

Acquired aplastic anemia is an immune-mediated disease characterized by severe defects in stem cell number resulting in hypocellular marrow and peripheral blood cytopenias. Minor paroxysmal nocturnal hemoglobinuria populations and a short telomere length were identified as predictive biomarkers of immunosuppressive therapy responsiveness in aplastic anemia. We enrolled 113 aplastic anemia patients (63 boys and 50 girls) in this study to evaluate their response to immunosuppressive therapy. The paroxysmal nocturnal hemoglobinuria populations and telomere length were detected by flow cytometry. Forty-seven patients (42%) carried a minor paroxysmal nocturnal hemoglobinuria population. The median telomere length of aplastic anemia patients was -0.99 standard deviation (SD) (range -4.01-+3.01 SD). Overall, 60 patients (53%) responded to immunosuppressive therapy after six months. Multivariate logistic regression analysis identified the absence of a paroxysmal nocturnal hemoglobinuria population and a shorter telomere length as independent unfavorable predictors of immunosuppressive therapy response at six months. The cohort was stratified into a group of poor prognosis (paroxysmal nocturnal hemoglobinuria negative and shorter telomere length; 37 patients) and good prognosis (paroxysmal nocturnal hemoglobinuria positive and/or longer telomere length; 76 patients), respectively. The response rates of the poor prognosis and good prognosis groups at six months were 19% and 70%, respectively (P<0.001). The combined absence of a minor paroxysmal nocturnal hemoglobinuria population and a short telomere length is an efficient predictor of poor immunosuppressive therapy response, which should be considered while deciding treatment options: immunosuppressive therapy or first-line hematopoietic stem cell transplantation. The trial was registered in www.umin.ac.jp with number UMIN000017972.

Similar outcome of upfront-unrelated and matched sibling stem cell transplantation in idiopathic paediatric aplastic anaemia. A study on behalf of the UK Paediatric BMT Working Party, Paediatric Diseases Working Party and Severe Aplastic Anaemia Working Party of EBMT

We explored the feasibility of unrelated donor haematopoietic stem cell transplant (HSCT) upfront without prior immunosuppressive therapy (IST) in paediatric idiopathic severe aplastic anaemia (SAA). This cohort was then compared to matched historical controls who had undergone first-line therapy with a matched sibling/family donor (MSD) HSCT (n = 87) or IST with horse antithymocyte globulin and ciclosporin (n = 58) or second-line therapy with unrelated donor HSCT post-failed IST (n = 24). The 2-year overall survival in the upfront cohort was 96 ± 4% compared to 91 ± 3% in the MSD controls (P = 0·30) and 94 ± 3% in the IST controls (P = 0·68) and 74 ± 9% in the unrelated donor HSCT post-IST failure controls (P = 0·02).The 2-year event-free survival in the upfront cohort was 92 ± 5% compared to 87 ± 4% in MSD controls (P = 0·37), 40 ± 7% in IST controls (P = 0·0001) and 74 ± 9% in the unrelated donor HSCT post-IST failure controls (n = 24) (P = 0·02). Outcomes for upfront-unrelated donor HSCT in paediatric idiopathic SAA were similar to MSD HSCT and superior to IST and unrelated donor HSCT post-IST failure. Front-line therapy with matched unrelated donor HSCT is a novel treatment approach and could be considered as first-line therapy in selected paediatric patients who lack a MSD.

Haploidentical BMT and post-transplant Cy for severe aplastic anemia: a multicenter retrospective study

Patients with refractory severe aplastic anemia (SAA) who lack a matched sibling or unrelated donor need new therapeutic approaches. Hematopoietic SCT (HSCT) using mismatched or haploidentical related donors has been used in the past, but was associated with a significant risk of GVHD and mortality. Recently, the use of post-transplant cyclophosphamide (Cy) has been shown to be an effective strategy to prevent GVHD in recipients of haploidentical HSCT, but the majority of reports have focused on patients with hematology malignancies. We describe the outcome of 16 patients who underwent haploidentical transplantation using a reduced-intensity conditioning regimen with post-transplant Cy. Stem cell sources were BM (N=13) or PBSCs (N=3). The rate of neutrophil engraftment was 94% and of platelet engraftment was 75%. Two patients had secondary graft failure and were successfully salvaged with another transplant. Three patients developed acute GVHD being grades 2-4 in two. Five patients have died and the 1-year OS was 67.1% (95% confidence interval: 36.5-86.4%). In our small series, the use of a reduced-intensity conditioning with post-transplant Cy in haploidentical BMT was associated with high rates of engraftment and low risk of GVHD in patients with relapsed/refractory SAA.

The combined use of cytokine-induced killer cells and cyclosporine a for the treatment of aplastic anemia in a mouse model

In this study, we investigated the combined use of cytokine-induced killer (CIK) cells and cyclosporine A (CsA) to treat a mouse model of aplastic anemia (AA). CIK cells were cultured and injected alone or in combination with CsA into mice that had previously been induced into AA by busulfan and mouse interferon-γ (IFN-γ). The CIK cell-treated group had a survival rate of 55%, which was similar to the 60% survival rate observed in the CsA-treated group. The combination group showed a survival rate as high as 90%, while none of the mice in the no-treatment group survived to the end of the experiment. The CIK cells produced multiple cytokines, including several hematopoietic growth factors, which could promote the expansion of mouse bone marrow mononuclear cells in vitro. CsA reduced the proportion of CD4(+) T cells and the level of IFN-γ. The combined CIK cell and CsA treatment exhibited the best curative effect, a finding that might be due to the influence of these factors on both hematopoiesis and immunity. These data suggest that the combination of CIK cells and immunosuppressive therapy might be a candidate therapy for AA in the future.

First-line treatment for severe aplastic anemia in children: bone marrow transplantation from a matched family donor versus immunosuppressive therapy

The current treatment approach for severe aplastic anemia in children is based on studies performed in the 1980s, and updated evidence is required. We retrospectively compared the outcomes of children with acquired severe aplastic anemia who received immunosuppressive therapy within prospective trials conducted by the Japanese Childhood Aplastic Anemia Study Group or who underwent bone marrow transplantation from an HLA-matched family donor registered in the Japanese Society for Hematopoietic Cell Transplantation Registry. Between 1992 and 2009, 599 children (younger than 17 years) with severe aplastic anemia received a bone marrow transplant from an HLA-matched family donor (n=213) or immunosuppressive therapy (n=386) as first-line treatment. While the overall survival did not differ between patients treated with immunosuppressive therapy or bone marrow transplantation [88% (95% confidence interval: 86-90) versus 92% (90-94)], failure-free survival was significantly inferior in patients receiving immunosuppressive therapy than in those undergoing bone marrow transplantation [56% (54-59) versus 87% (85-90); P<0.0001]. There was no significant improvement in outcomes over the two time periods (1992-1999 versus 2000-2009). In multivariate analysis, age <10 years was identified as a favorable factor for overall survival (P=0.007), and choice of first-line immunosuppressive therapy was the only unfavorable factor for failure-free survival (P<0.0001). These support the current algorithm for treatment decisions, which recommends bone marrow transplantation when an HLA-matched family donor is available in pediatric severe aplastic anemia.

Outcome of children with severe acquired aplastic anemia treated with rabbit antithymocyte globulin and cyclosporine A

OBJECTIVE

To evaluate the outcome of children with severe acquired aplastic anemia treated with rabbit antithymocyte globulin and cyclosporine as first-line treatment at this institution.

METHODS

Retrospective analysis of 26 pediatric patients with aplastic anemia, treated between 1996 and 2011 with rabbit antithymocyte globulin plus cyclosporine.

RESULTS

The overall response rate at six months was 34.6% (9/26), and the cumulative incidence of relapse was 26.5% (95% confidence interval [CI]: 1.4%-66%) at 5 years. The cumulative incidence of clonal evolution after immunosuppressive therapy was 8.3% (95% CI: 0.001%-53.7%) at five years with both clonal evolutions in non -responders who acquired monosomy 7 karyotype. The overall survival at five years was 73.6% (95% CI: 49.2%-87.5%).

CONCLUSIONS

The present results confirm the poor response rate with rabbit antithymocyte globulin as first therapy in pediatrics patients, similar to what has been reported for patients of all ages. This confirmation is problematic in Brazil, given the lack of horse antithymocyte globulin in many markets outside the United States.

Diagnosis and treatment of pediatric acquired aplastic anemia (AAA): an initial survey of the North American Pediatric Aplastic Anemia Consortium (NAPAAC)

BACKGROUND

Randomized clinical trials in pediatric aplastic anemia (AA) are rare and data to guide standards of care are scarce.

PROCEDURE

Eighteen pediatric institutions formed the North American Pediatric Aplastic Anemia Consortium to foster collaborative studies in AA. The initial goal of NAPAAC was to survey the diagnostic studies and therapies utilized in AA.

RESULTS

Our survey indicates considerable variability among institutions in the diagnosis and treatment of AA. There were areas of general consensus, including the need for a bone marrow evaluation, cytogenetic and specific fluorescent in situ hybridization assays to establish diagnosis and exclude genetic etiologies with many institutions requiring results prior to initiation of immunosuppressive therapy (IST); uniform referral for hematopoietic stem cell transplantation as first line therapy if an HLA-identical sibling is identified; the use of first-line IST containing horse anti-thymocyte globulin and cyclosporine A (CSA) if an HLA-identical sibling donor is not identified; supportive care measures; and slow taper of CSA after response. Areas of controversy included the need for telomere length results prior to IST, the time after IST initiation defining a treatment failure; use of hematopoietic growth factors; the preferred rescue therapy after failure of IST; the use of specific hemoglobin and platelet levels as triggers for transfusion support; the use of prophylactic antibiotics; and follow-up monitoring after completion of treatment.

CONCLUSIONS

These initial survey results reflect heterogeneity in diagnosis and care amongst pediatric centers and emphasize the need to develop evidence-based diagnosis and treatment approaches in this rare disease.

Effect of Tianshengyuan-1 (TSY-1) on telomerase activity and hematopoietic recovery - in vitro, ex vivo, and in vivo studies

Aplastic anemia is a heterogeneous disorder of bone marrow failure syndrome. Accumulating evidence indicates that both acquired and congenital aplastic anemia is linked to telomerase activity and telomere length. Chinese herbal medicine Tianshengyuan-1 (TSY-1), a liquid extraction of multiple Chinese herbs, appears to stimulate hematopoiesis in patients with bone marrow deficiencies; however, the exact mechanism of action remains unclear. In this study, we investigated the effect of TSY-1 on telomere length and telomerase activity. We first investigated the effects of TSY on in vitro cultured cell lines including CD34+ hepatic stem cells and CD4+/CD8- Jurkat cells. An immune-mediated murine aplastic anemia model and human samples, including peripheral blood samples of 4 healthy donors and bone marrow hematopoietic cells from 4 patients with hypocellular myelodysplastic syndrome (MDS), were also used to test the efficacy of TSY on hematopoiesis, telomerase activity and telomere length. Our results indicated that TSY-1 increased the telomerase activity and telomere length in a dose-response manner in vitro, in vivo, and in human samples including 3 of 4 healthy individuals and 3 of 4 bone marrow samples from MDS patients. In immune-mediated murine aplastic anemia model, TSY-1 activity on Telomere length was parallel to the significant increasing of the RBC, hemoglobin, hematocrit, and platelet count in peripheral blood, increasing of CD34+ cell count and hematopoiesis, and decreasing of fatty infiltration in bone marrow samples. Our study demonstrated that TSY-1 may exert its effects by modulating telomerase activity of hematopoietic cells. Further studies are warranted to explore the precise molecular mechanisms of how TSY-1 regulates telomerase activity and telomere length, and also to test the TSY-1 in randomized control trials.

Hematopoietic stem cell transplantation in children and young adults with secondary myelodysplastic syndrome and acute myelogenous leukemia after aplastic anemia

Secondary myelodysplastic syndrome and acute myelogenous leukemia (sMDS/sAML) are the most serious secondary events occurring after immunosuppressive therapy in patients with aplastic anemia. Here we evaluate the outcome of hematopoietic stem cell transplantation (HSCT) in 17 children and young adults with sMDS/sAML after childhood aplastic anemia. The median interval between the diagnosis of aplastic anemia and the development of sMDS/sAML was 2.9 years (range, 1.2 to 13.0 years). At a median age of 13.1 years (range, 4.4 to 26.7 years), patients underwent HSCT with bone marrow (n = 6) or peripheral blood stem cell (n = 11) grafts from HLA-matched sibling donors (n = 2), mismatched family donors (n = 2), or unrelated donors (n = 13). Monosomy 7 was detected in 13 patients. The preparative regimen consisted of busulfan, cyclophosphamide, and melphalan in 11 patients and other agents in 6 patients. All patients achieved neutrophil engraftment. The cumulative incidence of grade II-IV acute graft-versus-host disease (GVHD) was 47%, and that of chronic GVHD was 70%. Relapse occurred in 1 patient. The major cause of death was transplant-related complication (n = 9). Overall survival and event-free survival at 5 years after HSCT were both 41%. In summary, this study indicates that HSCT is a curative therapy for some patients with sMDS/sAML after aplastic anemia. Future efforts should focus on reducing transplantation-related mortality.

Acquired aplastic anemia in children

This article provides a practice-based and concise review of the etiology, diagnosis, and management of acquired aplastic anemia in children. Bone marrow transplantation, immunosuppressive therapy, and supportive care are discussed in detail. The aim is to provide the clinician with a better understanding of the disease and to offer guidelines for the management of children with this uncommon yet serious disorder.

Outcome of patients activating an unrelated donor search for severe acquired aplastic anemia

Patients with severe aplastic anemia (SAA) without a sibling donor receive immunosuppressive treatment (IST) with anti-thymocyte globulin (ATG). In the case of no response to IST, a voluntary unrelated donor (VUD) search is usually started. This study analyzes the outcome of ATG-refractory SAA patients activating a VUD search. Of 179 patients, 68 had at least one HLA-A, -B, and -DR matched donor identified and underwent HSCT while 50 also with a donor were not transplanted because of early death (8), late response to IST (34), transplant refusal (1), or other (7). Conversely, 61 had no matched donor, 13 of those ultimately received a mismatched HSCT. All but one received marrow stem cells. Among patients aged <17 years, those with at least one matched donor had a significant higher 4-year survival as compared to others (79% ± 6% versus 53% ± 10%, P = 0.01). There was also a survival advantage independent of recipient age when the donor search was initiated in the recent 2000-2005 study-period (74% ± 6% versus 47% ± 10%, P < 0.05). In multivariate analysis, the identification of a matched VUD tended to impact favourably on survival in patients with a recent donor search (P = 0.07). This study provides evidence for the use of unrelated donor HSCT in children and adults with IST-refractory SAA.

Prognostic value of telomere attrition in patients with aplastic anemia

The decision to pursue hematopoietic stem cell transplantation or immunosuppression as first therapy in severe aplastic anemia is currently based on age and availability of a histocompatible donor. The ability to predict hematologic response, relapse and clonal evolution could improve treatment allocation. In the past 15 years, telomeres have been implicated in clinical diseases such as aplastic anemia, pulmonary fibrosis, cirrhosis and cancer development. The clinical relevance of varying telomere lengths (TL) and/or mutations in genes of the telomerase complex (TERC, TERT) is evolving in aplastic anemia. A large retrospective analysis suggests that baseline TL associate with late events of hematologic relapse and clonal evolution in aplastic anemia patients treated initially with anti-thymocyte globulin-based therapy. Further laboratory experiments propose possible mechanistic insight into genomic instability of bone marrow cells derived from patients with critically short telomeres and/or mutation in telomerase genes. The possibility of modulating telomere attrition rate with sex hormones could positively affect clonal evolution rates in humans. This review will summarize studies in marrow failure that explore the association between telomeres and aplastic anemia outcomes.

Immune markers of disease severity and treatment response in pediatric acquired aplastic anemia

BACKGROUND

To investigate the immune status among pediatric patients with aplastic anemia (AA) and explore PNH-status, T-regulatory and NK-cell frequency as potential markers of clinical response.

METHODS

Data were retrospectively analyzed from twenty-six patients diagnosed with AA. PNH populations, T- and NK-subsets were determined via flow cytometry.

RESULTS

At diagnosis, 9/23 patients with severe AA (SAA) versus 1/3 with moderate AA (MAA) were PNH(pos) . Among PNH(pos) patients treated with ATG based immunosuppression, 2/6 had a complete response (CR), while 4/6 had a partial response (PR), similarly 2/6 PNH(neg) patients had a CR and 4/6 had a PR. Lymphocyte subset immunophenotyping revealed that T-regulatory cells represented 7.2% of total lymphocytes at diagnosis. Their frequency varied with disease severity (5.5% for SAA and 14.1% for MAA) and response (8.9% for CR and 1.5% for PR), generally increasing following therapy with IST (14.6%). The NK cell frequency was not substantially different based on disease severity or response.

CONCLUSIONS

Neither PNH cell populations, nor NK cell frequency corresponded with disease severity or response. T-regulatory cell frequency, although not statistically significant given the small sample size, corresponded with both severity and response, indicating potential utility as a prognostic tool.

Management of acquired aplastic anemia in children

The diagnosis of aplastic anemia in children requires exclusion of a variety of inherited or acquired BM failure syndromes with similar phenotypes. An efficient diagnostic plan is important because time from diagnosis to 'final' treatment is directly related to outcome regardless of the therapeutic option chosen. The gold standard of therapy remains hematopoietic SCT with a graft of BM cells for those children with matched sibling donors. Conversely for children without a sibling donor the high response and markedly improved overall survival rates of combined immunosuppressive therapy have proven robust, especially when horse derived anti-thymocyte globuline plus ciclosporine A are used. Incomplete response, relapse and progression to myelodysplasia/leukemia however have emerged as significant long-term issues. Improvements in outcome of alternative donor transplantation and the use of established and novel immunosuppressive agents provide multiple alternatives for treating refractory or relapsed patients. Regardless of the type of therapeutic approach, patients require centralized treatment in a center of excellence, ongoing monitoring for recurrence of disease and/or therapy-related immediate side effects and long-term effects.

Aplastic anemia: therapeutic updates in immunosuppression and transplantation

Advances in hematopoietic stem cell transplantation (HSCT) and immunosuppressive therapy (IST) have improved survival in severe aplastic anemia (SAA) from 10%-20% in the 1960s to 80%-90% today. A matched sibling HSCT is the treatment of choice in younger patients, whereas IST is often used in older patients or in those who lack a histocompatible sibling. Graft rejection, GVHD, and poor immune reconstitution (with associated infectious complications) limit the success of HSCT, whereas lack of response, relapse, and clonal evolution limit the success of IST. The historically high rate of graft rejection in SAA is now less problematic in the matched setting, but with greater rates observed with unrelated and umbilical cord donors. The correlation of increasing age with the risk of GVHD and the significant morbidity and mortality of this transplantation complication continue to affect the decision to pursue HSCT versus IST as initial therapy in adults with SAA. Outcomes with matched unrelated donor HSCT have improved, likely due to better donor selection, supportive care, and improved transplantation protocols. Results with mismatched unrelated donor and umbilical HSCT are not as favorable, with higher rates of graft rejection, GVHD, and infectious complications. Investigation of several upfront alternative IST protocols has not improved outcomes beyond horse antithymocyte globulin and cyclosporine. More recently, the role of alemtuzumab in SAA has been better defined and an oral thrombomimetic, eltrombopag, is showing promising activity in refractory cases. The most recent advances in HSCT and IST in SAA are discussed in this review.

Alternative donor HSCT in refractory acquired aplastic anemia - prevention of graft rejection and graft versus host disease by immunoablative conditioning and graft manipulation

Early alternative donor HSCT is a potentially curative therapeutic option for patients with AAA not responding to IST. Seven patients (median age at diagnosis, 11 yr) with refractory AAA without a MSD underwent HSCT from matched unrelated (n = 6) or haploidentical (n = 1) donors. Conditioning regimens included CY (n = 7), muromonab-CD3/ATG (n = 7), TT (n = 6), FLU (n = 5), and TLI (n = 2). Grafts were either CD34 purified and/or CD3/19 depleted and contained a median of 10.17 × 10(6) /kg CD34 and 5.5 × 10(4) /kg CD3 cells. All patients engrafted rapidly. Median time to leukocyte engraftment was 10 days. With a median follow-up of 26 (range, 11-153) months, six patients are alive and well with complete donor hematopoiesis. One heavily pretreated patient developed GVHD grade III and died from progressive renal failure (resulting from microangiopathic hemolytic anemia) and disseminated aspergillosis. Early alternative donor HSCT can help to avoid complications from prolonged IST and presumably improve survival of patients with refractory AAA. Administration of high doses of CD34 purified and/or CD3/19 depleted stem cells following novel immunoablative conditioning may prevent graft rejection and GVHD. However, a long interval from diagnosis to HSCT seems to be associated with poor outcome.

Success of allogeneic marrow transplantation for children with severe aplastic anaemia

Allogeneic marrow transplantation offers curative therapy for children with severe aplastic anaemia (SAA). We report the outcomes of 148 children with SAA who received human leucocyte antigen (HLA)-matched related marrow grafts between 1971 and 2010. Patients were divided into three groups, reflecting changes in conditioning and graft-versus-host disease (GVHD) prophylaxis regimens that occurred over time. Patients in Group 1 were conditioned with cyclophosphamide (CY; 200 mg/kg) followed by 'long' (102 d) methotrexate (MTX). Patients in Groups 2 and 3 received CY alone (Group 2) or combined with anti-thymocyte globulin (Group 3) followed by 'short' (days 1, 3, 6, and 11) MTX and ciclosporin (until day 180). With a median follow-up of 25 years, the 5-year survivals were 66%, 95%, and 100% for Groups 1, 2, and 3, respectively (overall P < 0·0001). The 3-year estimates of graft rejection were 22%, 32%, and 7%, respectively. The probabilities of grades III-IV acute and 2-year chronic GVHD were 15%, 0%, and 3%, and 21%, 21%, and 10%, respectively. Advances in preparative and GVHD prophylaxis regimens, and supportive care during the past 40 years have led to improved outcomes for children with SAA. These results confirm the use of allogeneic marrow transplantation for children with SAA who have HLA-matched related donors.

How I treat acquired aplastic anemia

Survival in severe aplastic anemia (SAA) has markedly improved in the past 4 decades because of advances in hematopoietic stem cell transplantation, immunosuppressive biologics and drugs, and supportive care. However, management of SAA patients remains challenging, both acutely in addressing the immediate consequences of pancytopenia and in the long term because of the disease's natural history and the consequences of therapy. Recent insights into pathophysiology have practical implications. We review key aspects of differential diagnosis, considerations in the choice of first- and second-line therapies, and the management of patients after immunosuppression, based on both a critical review of the recent literature and our large personal and research protocol experience of bone marrow failure in the Hematology Branch of the National Heart, Lung, and Blood Institute.

Antithymocyte globulin and cyclosporine in children with aplastic anemia: a developing country experience

BACKGROUND

Human leukocyte antigen-matched bone marrow transplant in the treatment of aplastic anemia is generally not feasible in developing countries due to lack of resources and expertise and immunosuppressive therapy (IST) has been used as an alternative. This study aims to report the long-term outcome of children with aplastic anemia treated with IST [antithymocyte globulin (ATG) and cyclosporine] in our hospital.

PROCEDURE

Case files of children with aplastic anemia who received IST from January 2001 to November 2009 were reviewed.

RESULTS

Thirty-five patients with aplastic anemia (14 very severe aplastic anemia; 21 severe aplastic anemia) were given IST. Seven patients expired within 3 months of therapy and were excluded. The analysis was done in 28 patients (24 male and 4 female; 12 very severe aplastic anemia and 16 severe aplastic anemia). The median age was 10 years (range, 5 to 12 y). Ten patients achieved partial response and 4 patients complete response at 1 year with overall response rate of 50%. Three nonresponders received a second course of ATG after 12 months out of which 2 responded. Hence, overall response including second course was 16 (57%). Three patients relapsed after a median interval of 23 months. The median duration of follow-up of 16 responders was 40 months (range, 15 to 119 mo). In the patients with long-term follow-up for >4 years (n = 7), all were surviving and independent of transfusions.

CONCLUSIONS

In a developing country setting, IST with ATG and cyclosporine seems to be a good alternative treatment for aplastic anemia in children.

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.

How I manage aplastic anaemia in children

Aplastic anaemia (AA) is a rare heterogeneous condition in children. 15-20% of cases are constitutional and correct diagnosis of these inherited causes of AA is important for appropriate management. For idiopathic severe aplastic anaemia, a matched sibling donor (MSD) haematopoietic stem cell transplant (HSCT) is the treatment of choice. If a MSD is not available, the options include immunosuppressive therapy (IST) or unrelated donor HSCT. IST with horse anti-thymocyte globulin (ATG) is superior to rabbit ATG and has good long-term results. In contrast, IST with rabbit ATG has an overall response of only 30-40%. Due to improvements in outcome over the last two decades in matched unrelated donor (MUD) HSCT, results are now similar to that of MSD HSCT. The decision to proceed with IST with ATG or MUD HSCT will depend on the likelihood of finding a MUD and the differing risks and benefits that each therapy provides.

Survival after immunosuppressive therapy in children with aplastic anemia

OBJECTIVE

To determine the survival of children =18 y, treated with immunosuppressive therapy (IST) using equine antithymocyte globulin (e-ATG) and cyclosporine (CsA).

DESIGN

Prospective data entry as per a specified format.

SETTING

Tertiary care hospital.

PATIENTS

From January 1998 to December 2009, 40 children were diagnosed with acquired aplastic anemia; 33 patients, who received IST, were analyzed. 31 children (94%) received one course of e-ATG and CsA. 2 patients (6%) received two courses of ATG.

INTERVENTION

Immunosuppressive therapy using equine ATG and cyclosporine.

MAIN OUTCOME MEASURES

Overall response and overall survival.

RESULTS

The overall response (complete response + partial response) to IST at 6 months was 87.9%. 8 (24.2%) patients achieved CR, 21 (63.6%) patients had PR and 4 (12.1%) patients did not respond to IST. Median follow-up was 24 (6-102) months. Overall survival at 24 months was 90%, with an actual survival of 85.4% at 5 years. Seventeen patients (51.5%) received G-CSF for a median duration of 32 (23-64) days. The patients who received G-CSF had fewer infectious complications (P=0.002), but G-CSF administration did not influence survival/ outcome. No patient developed myelodysplastic syndrome or acute leukemia.

CONCLUSIONS

The survival of patients who respond to IST is excellent. Also, G-CSF reduces the infectious complications without conferring any survival advantage.

IgG antibodies to ATG early after pediatric hematopoietic SCT increase the risk of acute GVHD

Anti-thymocyte globulin (ATG), raised in rabbits, is frequently used in allogeneic hematopoietic SCT (HSCT), to prevent graft rejection and acute GVHD. In solid organ transplant patients, antibodies to rabbit IgG result in an enhanced clearance of ATG. The occurrence of such antibodies in HSCT recipients and their clinical impact is unknown. Concentrations of ATG and anti-ATG antibodies were measured in 72 pediatric HSCT recipients treated with ATG as part of the conditioning. Anti-ATG antibodies were detected in 20 children (28%), all transplanted with a non-depleted graft. IgG anti-ATG, alone or combined with IgM and/or IgA anti-ATG, appeared in 10 children. Four patients developed IgG anti-ATG antibodies early (before day 22) post-HSCT. They had steep drops in ATG levels and showed rapid T-cell recovery, which was associated with a significantly increased risk of acute GVHD. In six patients IgG anti-ATG responses occurred later (range 28-46 days) after HSCT without an increased risk of GVHD. A total of 10 children only mounted an IgM (and IgA) anti-ATG response, which was without major impact on ATG levels. These results indicate that early development of IgG anti-ATG antibodies has a major impact on acute GVHD. Routine analysis ATG/anti-ATG Ab measurement should be considered.

Immunosuppressive therapy without hematopoietic growth factor exposure in pediatric acquired aplastic anemia

Immunosuppressive therapy (IST) is recommended for children with acquired aplastic anemia (AA) who lack a human leukocyte antigen (HLA)-matched sibling donor for hematopoietic cell transplantation (HCT). Hematopoietic growth factors have often been included in IST supportive care, but prolonged exposure may increase the risk of secondary clonal evolution. The authors evaluated response, survival, and the incidence of clonal evolution following cyclosporine-based IST without hematopoietic growth factor exposure in a population-based pediatric cohort, identified retrospectively. Forty-five patients with a median age of 7.3 years (range 1.2-17.0 years) were included. Partial (PR) and complete (CR) response was achieved in 82% and 64%, at a median of 55 days (range 11-414 days) and 7.6 months (range 2.8-82.2 months), respectively. Patients with associated seronegative hepatitis had an increased likelihood of PR and CR on multivariate analyses (PR: hazard ratio [HR] 3.15, 95% confidence interval [CI] 1.40, 7.11; CR: HR 2.99, 95% CI 1.35, 6.62), whereas older children were less likely to achieve IST response than children younger than 5 years at diagnosis. Five- and 10-year overall survival was 96% ± 4% and 90% ± 7%, respectively, and 5-year failure-free survival was 63% ± 8%. There was no infection-related mortality, although 16.4% of patients had at least 1 episode of documented bacteremia. The 5-year cumulative incidence of relapse was 12.9% and of clonal evolution was 3.2%. The authors conclude that children with AA who receive IST without hematopoietic growth factor support have excellent response and survival outcomes and a low incidence of clonal evolution.

Relapse of aplastic anemia in children after immunosuppressive therapy: a report from the Japan Childhood Aplastic Anemia Study Group

BACKGROUND

Although the therapeutic outcome of acquired aplastic anemia has improved markedly with the introduction of immunosuppressive therapy using antithymocyte globulin and cyclosporine, a significant proportion of patients subsequently relapse and require second-line therapy. However, detailed analyses of relapses in aplastic anemia children are limited.

DESIGN AND METHODS

We previously conducted two prospective multicenter trials of immunosuppressive therapy for children with aplastic anemia: AA-92 and AA-97, which began in 1992 and 1997, respectively. In this study, we assessed the relapse rate, risk factors for relapse, and the response to second-line treatment in children with aplastic anemia treated with antithymocyte globulin and cyclosporine.

RESULTS

From 1992 to 2007, we treated 441 children with aplastic anemia with standard immunosuppressive therapy. Among the 264 patients who responded to immunosuppressive therapy, 42 (15.9%) relapsed. The cumulative incidence of relapse was 11.9% at 10 years. Multivariate analysis revealed that relapse risk was significantly associated with an immunosuppressive therapy regimen using danazol (relative risk, 3.15; P=0.001) and non-severe aplastic anemia (relative risk, 2.51; P=0.02). Seventeen relapsed patients received additional immunosuppressive therapy with antithymocyte globulin and cyclosporine. Eight patients responded within 6 months. Seven of nine non-responders to second immunosuppressive therapy received hematopoietic stem cell transplantation and five are alive. Eleven patients underwent hematopoietic stem cell transplantation directly and seven are alive.

CONCLUSIONS

In the present study, the cumulative incidence of relapse at 10 years was relatively low compared to that in other studies mainly involving adult patients. A multicenter prospective study is warranted to establish optimal therapy for children with aplastic anemia.

Predicting response to immunosuppressive therapy in childhood aplastic anemia

In aplastic anemia, predictive markers of response to immunosuppressive therapy have not been well defined. We retrospectively evaluated whether clinical and laboratory findings before treatment could predict response in a pediatric cohort from the multicenter AA-97 study in Japan. Between 1997 and 2006, 312 newly diagnosed children were enrolled and treated with a combination of antithymocyte globulin and cyclosporine. In multivariate analyses, lower white blood cell count was the most significant predictive marker of better response; patients with white blood cell count less than 2.0×10(9)/L showed a higher response rate than those with white blood cell count of 2.0×10(9)/L or more (P=0.0003), followed by shorter interval between diagnosis and therapy (P=0.01), and male sex (P=0.03). In conclusion, pre-treatment clinical and laboratory findings influence response to therapy. The finding that response rate worsens with increasing interval between diagnosis and treatment highlights the importance of prompt immunosuppressive therapy for patients with aplastic anemia.

Diagnosis and management of aplastic anemia

Aplastic anemia remains a diagnosis of exclusion. Our ability to reliably diagnose, and therefore exclude, a variety of inherited or acquired diseases with similar phenotypes has improved markedly. An efficient diagnostic plan is important because time from diagnosis to treatment is related to outcome regardless of the therapeutic option chosen. HSCT remains the mainstay of therapy for those with matched sibling donors, and results have improved even further in recent years. For those without a sibling donor, the high response and overall survival rates of combined immunosuppressive therapy (IST) have proven robust. Nonetheless, incomplete response, relapse, and progression to myelodysplasia/leukemia have more clearly emerged as significant long-term issues. Improvements in outcome of alternative donor transplantation and the use of established and novel immunosuppressive agents provide multiple alternatives for treating refractory or relapsed patients. Best practices in this regard are not yet clearly established and may vary by a variety of demographic and treatment-specific factors. Regardless of the type of therapeutic approach, patients require ongoing monitoring for occurrence of disease and/or therapy-related side effects.

Cytokine signature profiles in acquired aplastic anemia and myelodysplastic syndromes

Although aplastic anemia and myelodysplasia have been extensively investigated, little is known about their circulating cytokine patterns. We compared plasma soluble cytokines in 33 aplastic anemia, 57 myelodysplasia patients, and 48 healthy controls. High levels of thrombopoietin and granulocyte colony-stimulating factor, with low levels of CD40 ligand, chemokine (C-X-C motif) ligand 5, chemokine (C-C motif) ligand 5, chemokine (C-X-C motif) ligand 11, epidermal growth factor, vascular endothelial growth factor, and chemokine (C-C motif) ligand 11 were a signature profile for aplastic anemia. High levels of tumor necrosis factor-α, interleukin-6, chemokine (C-C motif) ligand 3, interleukin-1 receptor antagonist, and hepatocyte growth factor were a cytokine signature for myelodysplasia. Despite similar clinical presentations, distinct cytokine profiles were observed between aplastic anemia and hypocellular myelodysplasia. Future studies focusing on cytokines that better discriminate these two entities such as thrombopoietin and chemokine (C-C motif) ligand 3 may be useful tools in clinical practice.

High-dose cyclophosphamide treatment for refractory severe aplastic anemia in children

OBJECTIVE

To determine if high-dose cyclophosphamide is an effective therapy for children with refractory severe aplastic anemia (SAA).

BACKGROUND

SAA is an illness characterized by the depletion of hematopoietic precursors associated with life-threatening complications. Hematopoietic stem cell transplant (HSCT) is the treatment of choice if a human leukocyte antigen (HLA)-related donor is available. Immunosuppression with anti-thymocyte globulin (ATG) and cyclosporine A (CSA) is an option for patients who are not HSCT candidates. Unrelated donor HSCT has been used with limited success. High-dose cyclophosphamide has been used successfully in the treatment of adults with SAA, but experience in children is limited.

PROCEDURE

Five pediatric patients who had failed previous immunosuppressive therapy for SAA were treated with high-dose cyclophosphamide (45 mg/kg/day x 4 days).

RESULTS

After 12 months of treatment, two of five patients experienced a complete response with high-dose cyclophosphamide therapy. The two complete responders achieved red cell recovery with a hematocrit of >36% at days 212 and 112 and platelet recovery with a platelet count of >100 x 10(9)/L at days 126 and 324. Of the remaining patients, one patient failed to respond, and two patients expired from infectious complications.

CONCLUSIONS

High-dose cyclophosphamide can lead to complete responses in children with SAA who have failed to respond to traditional immunosuppressive therapy.

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.

Tacrolimus as an alternative to cyclosporine in the maintenance phase of immunosuppressive therapy for severe aplastic anemia in children

OBJECTIVE

Given the paucity of data on the use of agents other than cyclosporine (CsA) in the maintenance phase of immunosuppressive therapy (IST) for severe aplastic anemia (SAA) in children, we sought to describe our experience with tacrolimus in pediatric SAA, and to compare outcomes with a preceding series of patients who received CsA.

METHODS

Eight patients with SAA diagnosed between 2003 and 2008 for whom no human leukocyte antigen (HLA)-matched sibling donor was identified underwent tacrolimus-based IST. These children were compared with a previously described series of 13 patients who had undergone CsA-based IST at our institution between 1990 and 2003. All patients initially received equine antithymocyte globulin (ATG) and corticosteroids.

RESULTS

Complete response (CR) rate was 88% for tacrolimus and 85% for CsA. Median time to CR was approximately 7 months in both groups. Median follow-up duration was 2.4 years for tacrolimus and 8.4 years for CsA. Among responders with de novo SAA, relapse rate was 25% (n = 1) at 2 years for tacrolimus and 0% at 2 years and 23% (n = 3) at 5 years for CsA; no significant difference in relapse-free survival was detected between the two groups (P = 0.07). Paroxysmal nocturnal hemoglobinuria was seen in one patient on tacrolimus who had relapsed after CsA-based IST. Tacrolimus-based IST was well-tolerated.

CONCLUSION

These data provide evidence that tacrolimus may be a suitable alternative to CsA as part of an IST regimen for SAA in children who lack an HLA-matched sibling and may have a more favorable profile of side effects than CsA.

Finding the needle in the hay stack: hematopoietic stem cells in Fanconi anemia

Fanconi anemia is a rare bone marrow failure and cancer predisposition syndrome. Childhood onset of aplastic anemia is one of the hallmarks of this condition. Supportive therapy in the form of blood products, androgens, and hematopoietic growth factors may boost blood counts temporarily. However, allogeneic hematopoietic stem cell transplantation (HSCT) currently remains the only curative treatment option for the hematologic manifestations of Fanconi anemia (FA). Here we review current clinical and pre-clinical strategies for treating hematopoietic stem cell (HSC) failure, including the experience with mobilizing and collecting CD34+ hematopoietic stem and progenitor cells as target cells for somatic gene therapy, the current state of FA gene therapy trials, and future prospects for cell and gene therapy.

Immune-mediated adverse drug reactions

Many adverse drug reactions are mediated by the immune system. This can be because the therapeutic effect of the drug targets the immune system. For example, immunosuppressive drugs increase the risk of infections. It is paradoxical that some immunosuppressive drugs can lead to autoimmune reactions. Another mechanism by which drugs can cause an adverse reaction involves an idiosyncratic response to the drug such as an immune-mediated skin rash. These idiosyncratic drug reactions (IDRs) are difficult to study because of the paucity of valid animal models and their unpredictable nature. Therefore, much of our mechanistic knowledge of IDRs is based on inferences from the clinical characteristics of IDRs rather than on controlled mechanistic studies. In general, IDRs are associated with a delay between starting the drug and the onset of the adverse reaction, and the typical delay is different for different types of IDRs. In contrast, on rechallenge, there is usually a rapid onset of the adverse reaction, which is characteristic of an amnestic immune response. The absence of such a rapid response is usually considered evidence that an IDR is not immune-mediated; yet, there are immune-mediated IDRs that do not have an amnestic response. One possible reason for the lack of an amnestic response is if the IDR has a strong autoimmune component leading to deletion of autoimmune memory cells when the drug is withdrawn. Another interesting characteristic of IDRs is that there are many drugs that can cause different types of IDRs in different patients. A possible explanation is that although the immune response is induced by a drug, it is directed against an autoantigen, and interindividual differences in the immune repertoire determine which autoantigen and target organ are affected. Although testing these hypotheses represents a difficult challenge, the importance of these adverse reactions makes it a high priority.

Predicting response to immunosuppressive therapy and survival in severe aplastic anaemia

Horse anti-thymocyte globulin (h-ATG) and ciclosporin are the initial therapy for most patients with severe aplastic anaemia (SAA), but there is no practical and reliable method to predict response to this treatment. To determine whether pretreatment blood counts discriminate patients with SAA who have a higher likelihood of haematological response at 6 months to immunosuppressive therapy (IST), we conducted a single institution retrospective analysis on 316 SAA patients treated with h-ATG-based IST from 1989 to 2005. In multivariate analysis, younger age, higher baseline absolute reticulocyte count (ARC), and absolute lymphocyte count (ALC) were highly predictive of response at 6 months. Patients with baseline ARC > or = 25 x 10(9)/l and ALC > or = 1 x 10(9)/l had a much greater probability of response at 6 months following IST compared to those with lower ARC and ALC (83% vs. 41%, respectively; P < 0.001). This higher likelihood of response translated to greater rate of 5-year survival in patients in the high ARC/ALC group (92%) compared to those with a low ARC/ALC (53%). In the era of IST, the baseline ARC and ALC together serve as a simple predictor of response following IST, which should guide in risk stratification among patients with SAA.