Autologous Peripheral Blood Stem Cell Transplantation for Severe Multiple Sclerosis

We describe the results of a clinical trial to evaluate the feasibility and toxicity of autologous hematopoietic stem cell transplantation (auto-HSCT) for patients with progressive multiple sclerosis (MS). Fifteen patients (all patients with secondary progressive MS) were enrolled. The median expanded disability status scale (EDSS) score at baseline was 6.0 (range, 4.5-7.5). Peripheral blood stem cells were obtained by leukapheresis after mobilization with granulocyte colony-stimulating factor. In 9 patients, CD34+ cell selection was performed with a CliniMACS cell selection system, and 6 patients accepted infusion of unmodified peripheral blood stem cells. The modified BEAM (carmustine, teniposide, cytarabine, and melphalan) was the sole conditioning regimen used. The adverse effects included infections, mucositis, transient hepatotoxicity, and diarrhea. Three patients had flares of neurologic deterioration during mobilization, 8 patients had the same manifestation during transplantation, and 2 patients had similar flares within 3 months of transplantation. Six patients experienced continuous neurologic improvement after transplantation, 5 patients experienced neurologic progression, and 4 patients had stabilization of their disease. The confirmed progression-free rate was 63.8% at 49 months. The results of lymphocyte purging were no better than for no purging. Auto-HSCT proved to be safe and beneficial for some MS patients. Further studies are needed to establish the merit of this procedure for MS patients.     

CD34+ selected autologous peripheral blood stem cell transplantation for multiple sclerosis: report of toxicity and treatment results at one year of follow-up in 15 patients

BACKGROUND AND OBJECTIVES: Autologous stem cell transplantation (ASCT) is currently being evaluated as a therapy for patients with multiple sclerosis (MS). We report the results of a phase II trial to evaluate feasibility and toxicity of CD34+ selected ASCT (CD34+/ASCT) and treatment results at one year of follow-up. DESIGN AND METHODS: Patients with advanced secondary progressive (SP) or relapsing-remitting (RR) MS and confirmed worsening of the extended disability status scale (EDSS) in the previous year despite interferon or other immunotherapies were included. Peripheral blood stem cells were obtained by leukaphereses after mobilization with cyclophosphamide (Cy) and granulocyte colony-stimulating factor (G-CSF). CD34+ selection was performed by means of an Isolex 300 or CliniMACS device. BCNU, Cy and antithymocyte globulin (ATG) were administered as conditioning regimen. RESULTS: Fifteen patients (9 SPMS and 6 RRMS) with a median EDSS of 6.0 (4.5-6.5) and a median of 3 (1-7) relapses in the previous year were included. Mobilization was unsuccessful in one patient. During mobilization, one patient had a transient neurologic deterioration. The main complication during ASCT were engraftment syndrome, which developed in three patients, CMV reactivation in one, and neurologic deterioration in two patients coinciding with high-fever related to ATG. Hematologic recovery was fast and complete in all cases. At 12 months, the EDSS had improved in three patients, worsened in two and remained stable in nine. Despite withdrawal of all immunosuppressive therapy only two patients had relapses. Magnetic resonance imaging showed disappearance of enhanced T1 lesions but oligoclonal bands persisted in the cerebrospinal fluid of all evaluated cases. INTERPRETATION AND CONCLUSIONS: CD34+/ASCT using BCNU, Cy and ATG as conditioning regimen has an acceptable toxicity and clearly reduces the progression of MS. Further follow-up is necessary to establish the real impact of this procedure on the long-term evolution of the disease.     

High-dose immunosuppressive therapy with PBPC support in the treatment of poor risk multiple sclerosis

High-dose immunoablative chemotherapy with autologous haematopoietic cell support might be beneficial in the treatment of intractable forms of MS. We mobilised PBPC in 11 patients with secondary progressive MS and finally eight patients were grafted after high-dose BEAM chemotherapy with either in vitro or in vivo T cell depletion. Median EDSS and SNRS scores at the time of inclusion were 6.5 (6.5-7.5) and 56 (44-65), respectively. PBPC mobilisation was safe with no serious adverse effects, and without significant aggravation of disability. One patient improved significantly (by 1.0 point on EDSS) after the mobilisation. Two mobilisation failures were observed. No life-threatening events occurred during the transplantation. All grafted patients, except one, at least stabilised their disability status. One patient improved significantly (by 1.5 points on EDSS), two patients improved slightly (by 0.5 points on EDSS), one patient worsened by 1.0 point on the EDSS in 10 months. Improvement occurred with a delay of 2-4 months. Median EDSS and SNRS of grafted patients at the last follow up were 6.5 (5.5-8.5) and 64 (39-73), respectively with median follow-up of 8.5 months. Further follow-up is needed to determine the disease course after complete immune reconstitution. Bone Marrow Transplantation (2000) 25, 525-531.     

Autologous hematopoietic cell transplantation following high-dose immunosuppressive therapy for advanced multiple sclerosis: long-term results

The purpose of the study was to determine the long-term safety and effectiveness of high-dose immunosuppressive therapy (HDIT) followed by autologous hematopoietic cell transplantation (AHCT) in advanced multiple sclerosis (MS). TBI, CY and antithymocyte globulin were followed by transplantation of autologous, CD34-selected PBSCs. Neurological examinations, brain magnetic resonance imaging and cerebrospinal fluid (CSF) for oligoclonal bands (OCB) were serially evaluated. Patients (n=26, mean Expanded Disability Status Scale (EDSS)=7.0, 17 secondary progressive, 8 primary progressive, 1 relapsing/remitting) were followed for a median of 48 months after HDIT followed by AHCT. The 72-month probability of worsening 1.0 EDSS point was 0.52 (95% confidence interval, 0.30-0.75). Five patients had an EDSS at baseline of 6.0; four of them had not failed treatment at last study visit. OCB in CSF persisted with minor changes in the banding pattern. Four new or enhancing lesions were seen on MRI, all within 13 months of treatment. In this population with high baseline EDSS, a significant proportion of patients with advanced MS remained stable for as long as 7 years after transplant. Non-inflammatory events may have contributed to neurological worsening after treatment. HDIT/AHCT may be more effective in patients with less advanced relapsing/remitting MS.     

High-dose immunosuppressive therapy with autologous hematopoietic stem cell transplantation as a treatment option in multiple sclerosis

High-dose immunosuppressive therapy (HDIT) with autologous hematopoietic stem cell transplantation (auto-HSCT) is a new and promising approach to the treatment of multiple sclerosis (MS) patients because currently there are no effective treatment methods for this disease. In this article, we present results of a prospective clinical study of efficacy of HDIT + auto-HSCT in MS patients. The following treatment strategies were employed in the study: "early," "conventional," and "salvage/late" transplantation. Fifty patients with various types of MS were included in this study. No toxic deaths were reported among 50 MS patients; transplantation procedure was well-tolerated by the patients. The efficacy analysis was performed in 45 patients. Twenty-eight patients achieved an objective improvement of neurological symptoms, defined as at least 0.5-point decrease in the Expanded Disability Status Scale (EDSS) score as compared to the baseline and confirmed during 6 months, and 17 patients had disease stabilization (steady EDSS level as compared to the baseline and confirmed during 6 months). The progression-free survival at 6 years after HDIT + auto-HSCT was 72%. Magnetic resonance imaging data were available in 37 patients before transplantation showing disease activity in 43.3%. No active, new, or enlarging lesions were registered in patients without disease progression. In conclusion, HDIT + auto-HSCT suggests positive results in management of patients with different types of MS. Identification of treatment strategies based on the level of disability, namely "early," "conventional," and "salvage/late" transplantation, appears to be feasible to improve treatment outcomes.     

Comparison of the clinical courses of the opticospinal and conventional forms of multiple sclerosis in Japan

We evaluated the clinical courses of 216 patients with multiple sclerosis (MS) diagnosed according to the recommended diagnostic criteria of McDonald et al (10). Sixty-five patients clinically displaying selective involvement of the optic nerves and spinal cord were classified as opticospinal MS (OS-MS), while the other 151 showing disseminated involvement of the central nervous system were classified as conventional MS (C-MS). The disease duration did not differ significantly between the two subtypes (11.2 years vs. 11.5 years). In addition to a higher age of onset, female preponderance and higher Kurtzke's expanded disability status scale (EDSS) scores, the OS-MS patients showed a markedly lower frequency of secondary progressive MS than the C-MS patients (4.6% vs. 29.1%, p=0.0001). The EDSS scores of the C-MS patients were significantly correlated with the disease duration, while those of the OS-MS patients were not. Among the C-MS patients, the frequency of secondary progressive MS was significantly more common in patients with a disease duration of more than 10 years than in those with a shorter duration. These results suggest that the irreversible disability in OS-MS is determined by relapses, rather than by chronic progression, whereas C-MS has a similar clinical course to MS in Westerners.     

High-dose immunosuppressive therapy and autologous peripheral blood stem cell transplantation for severe multiple sclerosis

There were 26 patients enrolled in a pilot study of high-dose immunosuppressive therapy (HDIT) for severe multiple sclerosis (MS). Median baseline expanded disability status scale (EDSS) was 7.0 (range, 5.0-8.0). HDIT consisted of total body irradiation, cyclophosphamide, and antithymocyte globulin (ATG) and was followed by transplantation of autologous, granulocyte colony-stimulating factor (G-CSF)-mobilized CD34-selected stem cells. Regimen-related toxicities were mild. Because of bladder dysfunction, there were 8 infectious events of the lower urinary tract. One patient died from Epstein-Barr virus (EBV)-related posttransplantation lymphoproliferative disorder (PTLD) associated with a change from horse-derived to rabbit-derived ATG in the HDIT regimen. An engraftment syndrome characterized by noninfectious fever with or without rash developed in 13 of the first 18 patients and was associated in some cases with transient worsening of neurologic symptoms. There were 2 significant adverse neurologic events that occurred, including a flare of MS during mobilization and an episode of irreversible neurologic deterioration after HDIT associated with fever. With a median follow-up of 24 (range, 3-36) months, the Kaplan-Meier estimate of progression (>/= 1.0 point EDSS) at 3 years was 27%. Of 12 patients who had oligoclonal bands in the cerebrospinal fluid at baseline, 9 had persistence after HDIT. After HDIT, 4 patients developed new enhancing lesions on magnetic resonance imaging of the brain. The estimate of survival at 3 years was 91%. Important clinical issues in the use of HDIT and stem cell transplantation for MS were identified; however, modifications of the initial approaches appear to reduce treatment risks. This was a heterogeneous high-risk group, and a phase 3 study is planned to fully assess efficacy.     

Therapeutic plasma exchange combined with immunomodulating agents in secondary progressive multiple sclerosis patients

Multiple sclerosis (MS) is the most common cause of neurological disability. Therapeutic plasma exchange (TPE) has been used in the management of patients with MS with equivocal efficacy. With this work we would like to present our experience with 10 patients (seven male and three female, mean age 34 years [range 27-53 years]) with secondary progressive MS, who were treated with immunomodulating agents and who also underwent TPE. The patients' expanded disability status scale (EDSS) score of entry to the study varied from 5.0 to 6.5. One year before study entry all patients showed a marked deterioration (12 months before starting TPE they had been rated 4.5-5.5 on the EDSS). TPE was performed three times a week for two weeks and thereafter once a week, or once a month for the stable patients. The machine used was the Cobe Spectra and albumin 5% was the replacement fluid. Peripheral veins were used in nine patients and indwelling vascular access was required in one patient. Eighteen months later, patients stopped taking the immunomodulating agent therapy and continued only with TPE. No side-effects occurred during the TPE session. After 36 months of TPE therapy, five patients were stabilized in their disability, while two patients showed a minor progression of the disease (an additional 0.5 degree in disability as determined by the EDSS). No relapses occurred during TPE. Three patients stopped the therapy: one patient because of persistent nausea and two patients for reasons unrelated to TPE. Periodic TPE was associated with reduced accumulation of neurological deficits (as documented by EDSS) in patients with secondary progressive MS.     

Clinical outcome of autologous peripheral blood stem cell transplantation in opticospinal and conventional forms of secondary progressive multiple sclerosis in a Chinese population

To evaluate clinical outcomes of autologous peripheral blood stem cell transplantation (APBCST) between opticospinal multiple sclerosis (OSMS) and conventional multiple sclerosis (CMS) during disease progressive stage in a Chinese population. Thirty-six secondary progressive MS patients, among whom 21 were with OSMS and 15 with CMS, underwent APBSCT and were followed up for an average of 48.92 months (range, 10–91 months). Peripheral blood stem cells were obtained by leukapheresis after mobilization with granulocyte colony-stimulating factor. Modified BEAM conditioning regimen (Tiniposide, melphalan, carmustin, and cytosine arabinoside) were administered. Outcomes were evaluated using the expanded disability status scale (EDSS). No maintenance treatment was administered if there was no disease progression. No treatment-related mortality occurred. Among the 36 patients, one OSMS patient dropped during the follow-up. Among the 22 relapse-free patients, 20 were with continuous neurological improvement without any relapse events, and two remained in neurologically stable states. Among the 13 relapse patients, seven had experienced of neurological relapse, but with no progression during the follow-up period; and six experienced neurological deterioration after transplantation and needed further immunosuppressant treatment. The confirmed relapse-free survival rate was 62.9% and progression-free survival rate was 83.3% after 91 months according to Kaplan and Meier survival curves. Eleven of the 20 OSMS patients (55%) and two of the 15 CMS patients (13.3%) stayed in disease active group (P = 0.014). For the 20 OSMS patients, the overall EDSS score decreased significantly after transplantation (P = 0.016), while visual functions had no significant improvement (P = 0.716). Progressive OSMS has a higher relapse rate than CMS following APBSCT.     

N-acetyl-L-cysteine improves outcome of advanced cerebral adrenoleukodystrophy

Hematopoietic stem cell transplantation as a treatment for childhood cerebral adrenoleukodystrophy (ALD) has historically only been successful in early disease. As ALD is associated with oxidative damage, we reasoned that adjunctive therapy with an antioxidant agent, N-acetyl-L-cysteine (NAC), may provide protection from rapid neurologic decline in boys with advanced cerebral disease. We report three boys with advanced ALD, whose neurologic status and brain radiographic findings were stabilized by treatment including NAC 8-11 months after hematopoietic stem cell transplantation. These results contrast with previous survival data in cerebral ALD patients who had a similar degree of brain involvement, all of whom died within 1 year of stem cell infusion despite a full donor engraftment. Thus, NAC merits investigation as a therapeutic strategy for patients with advanced ALD as an intervention that could change this lethal disease to a condition amendable to treatment with hematopoietic stem cell transplantation.     

Allogeneic T cells impair engraftment and hematopoiesis after stem cell transplantation

Because of the perception that depleting hematopoietic grafts of T cells will result in poorer immune recovery and in increased risk of graft rejection, pure hematopoietic stem cells (HSC), which avoid the potentially lethal complication of graft-versus-host disease (GVHD), have not been used for allogeneic hematopoietic cell transplantation (HCT) in humans. Ideal grafts should contain HSC plus mature cells that confer only the benefits of protection from pathogens and suppression of malignancies. This goal requires better understanding of the effects of each blood cell type and its interactions during engraftment and immune regeneration. Here, we studied hematopoietic reconstitution post-HCT, comparing grafts of purified HSC with grafts supplemented with T cells in a minor histocompatibility antigen (mHA)-mismatched mouse model. Cell counts, composition, and chimerism of blood and lymphoid organs were evaluated and followed intensively through the first month, and then subsequently for up to 1 yr. Throughout this period, recipients of pure HSC demonstrated superior total cell recovery and lymphoid reconstitution compared with recipients of T cell-containing grafts. In the latter, rapid expansion of T cells occurred, and suppression of hematopoiesis derived from donor HSC was observed. Our findings demonstrate that even early post-HCT, T cells retard donor HSC engraftment and immune recovery. These observations contradict the postulation that mature donor T cells provide important transient immunity and facilitate HSC engraftment.     

Seeing the good and bad in aplastic anemia: is autoimmunity in AA dysregulated or antineoplastic?

Aplastic anemia (AA) is considered to be an autoimmune disease directed against hematopoietic stem cells (HSC), though knowledge on the inciting autoantigen(s) is scant. According to the traditional concept of autoimmunity the target tissue in autoimmune disease is essentially normal, and misdirected self-attack is caused by disturbed self-recognition. Recently, this theory has been challenged by the hypothesis that autoimmunity against solid tissues is directed against intrinsically abnormal, transforming cells, i.e. autoimmune reactions are essentially antineoplastic, attempting to eliminate cells signalling 'danger'. This theory might apply to AA as well. Observations such as the dysplastic traits typical of non-severe AA, the high prevalence of one or several abnormal hematopoietic clones and their resistance to apoptosis in newly diagnosed AA patients suggest that these cell populations do not develop secondarily, but expand primarily und could be the primary target of AA, normal hematopoietic stem cells being destroyed as innocent bystanders. If bone marrow hypoplasia/aplasia indeed reflects an immune reaction incited by outgrowth of transformed cells, immunosuppressive treatment of AA would have to be reconsidered, since a two-edged sword. As a consequence, AA patients with a hyperreactive immune system may require more intense immunosuppressive therapy (IS), whereas patients with an anergic immune system may fare better with IS of lower intensity than the currently recommended standard.     

Absence of donor-derived keratinocyte stem cells in skin tissues cultured from patients after mobilized peripheral blood hematopoietic stem cell transplantation

OBJECTIVE: Recent studies suggest that primitive bone marrow-derived cells contribute to regeneration of many tissues, including muscle, endothelium, myocardium, neural tissues, liver, and skin. Conversely, primitive cells resident in muscle and other tissues have been reported to reconstitute hematopoiesis. We investigated the contribution of cells with a primitive hematopoietic phenotype to human epidermal skin formation in recipients of allogeneic mobilized peripheral blood hematopoietic stem cell (HSC) transplantation. PATIENTS AND METHODS: Our study population included female patients who had received granulocyte colony-stimulating factor mobilized peripheral blood HSC transplants from male donors for a variety of benign and malignant hematologic disorders at least 6 months before study entry, with a history of skin graft-vs-host disease. Epidermal skin cells (keratinocytes) obtained from punch biopsies of the skin were cultured under conditions specific for growth and expansion of homogenous populations of keratinocytes from keratinocyte stem cells. After multiple passages, DNA was extracted from cultured cells and evaluated by two different polymerase chain reaction (PCR) method for detection of Y chromosome specific sequences. RESULTS: Neither sensitive PCR-based technique revealed the presence of male donor-derived keratinocyte stem cells in keratinocytes cultured from skin biopsies of female allogeneic transplantation recipients. CONCLUSIONS: We could not confirm the contribution of donor mobilized peripheral blood hematopoietic stem cells to keratinocyte stem cell populations after HSC transplantation. These results cannot explain the presence of donor-derived cells with keratinocyte phenotypic markers in tissue sections of HSC transplant recipients.     

Ex vivo expansion of umbilical cord blood stem cells for transplantation: growing knowledge from the hematopoietic niche

Umbilical cord blood transplantation (UCBT) in adults is limited by the small number of primitive hematopoietic stem cells (HSC) in each graft, resulting in delayed engraftment post transplant, and both short- and long-term infectious complications. Initial efforts to expand UCB progenitors ex vivo have resulted in expansion of mature rather than immature HSC, confounded by the inability to accurately and reliably measure long-term reconstituting cells. Ex vivo expansion of UCB HSC has failed to improve engraftment because of resulting defects that promote apoptosis, disrupt marrow homing and initiate cell cycling. Here we discuss the future of ex vivo expansion, which we suggest will include the isolation of immature hematopoietic progenitors on the basis of function rather than surface phenotype and will employ both cytokines and stroma to maintain and expand the stem cell niche. We suggest that ex vivo expansion could be enhanced by manipulating newly discovered signaling pathways (Notch, Wnt, bone morphogenetic protein 4 and Tie2/angiopoietin-1) and intracellular mediators (phosphatase and tensin homolog and glycogen synthase kinase-3) in a manner that promotes HSC expansion with less differentiation. Improved methods for ex vivo expansion will make UCBT available to more patients, decrease engraftment times and allow more rapid immune reconstitution post transplant.     

Cotransplantation of ex vivo expanded mesenchymal stem cells accelerates lymphocyte recovery and may reduce the risk of graft failure in haploidentical hematopoietic stem-cell transplantation

Haploidentical hematopoietic stem-cell transplantation (HSCT) is associated with an increased risk of graft failure. Adult bone marrow-derived mesenchymal stromal cells (MSCs) have been shown to support in vivo normal hematopoiesis and to display potent immune suppressive effects. We cotransplanted donor MSCs in 14 children undergoing transplantation of HLA-disparate CD34(+) cells from a relative. While we observed a graft failure rate of 15% in 47 historic controls, all patients given MSCs showed sustained hematopoietic engraftment without any adverse reaction. In particular, children given MSCs did not experience more infections compared with controls. These data suggest that MSCs, possibly thanks to their potent immunosuppressive effect on alloreactive host T lymphocytes escaping the preparative regimen, reduce the risk of graft failure in haploidentical HSC transplant recipients.     

Bone marrow transplantation for the treatment of immune deficiency states

The first successful allogeneic bone marrow transplants were performed in children with severe combined immune deficiency (SCID). Bone marrow transplants for patients with SCID have been in the forefront of clinical bone marrow transplantation including the first successful use of T lymphocyte-depleted haploidentical bone marrow and matched unrelated donors. Successful bone marrow transplantation for most forms of SCID requires only the engraftment of donor lymphoid stem cells; donor hematopoietic stem cell engraftment is usually not required. The Wiskott-Aldrich syndrome was the first genetic disease involving the hematopoietic stem cell to be completely corrected by allogeneic bone marrow transplantation. The successful transplantation of Wiskott-Aldrich syndrome patients demonstrated that agents with adequate anti-lymphoid and hematopoietic stem cell activity were necessary in order to achieve complete donor lymphoid and hematopoietic stem cell engraftment. Initially, total body irradiation and now busulfan are used to ablate recipient hematopoietic stem cells, while cyclophosphamide is used to ablate recipient lymphoid stem cells. No single agent/drug is capable of eliminating both stem cell populations. Histocompatible bone marrow transplantation has a role in the treatment of patients with immune deficiency due to primary defects of the hematopoietic stem cell. The recent introduction of cytokines (gamma-interferon and granulocyte colony stimulating factor) may reduce the need for bone marrow transplantation for myeloid immune deficiency states. Initial attempts to treat patients with the acquired immune deficiency syndrome by bone marrow transplantation were limited by the lack of effective concomitant anti-viral therapy. Bone marrow transplantation for immune deficiency states continues to be in the forefront of human bone marrow transplantation.     

Reversal of autoimmune disease in lupus-prone New Zealand black/New Zealand white mice by nonmyeloablative transplantation of purified allogeneic hematopoietic stem cells

Patients with severe systemic lupus erythematosus (SLE) refractory to conventional treatment are candidates for autologous hematopoietic stem cell (HSC) transplantation if the intent is to reset the immunologic clock. These patients might be candidates for allotransplantation with (SLE)-resistant major histocompatibility complex (MHC) haplotype-matched HSC if partial or complete replacement of an autoimmune-prone system is the intent. Using lupus-prone New Zealand black x New Zealand white (NZBW) mice, we investigated the use of highly enriched, haplomismatched, allogeneic HSC to prevent development of or to treat established autoimmune pathology. Young NZBW mice receiving purified allogeneic HSC transplants had improved survival, decreased proteinuria, circulating immune complexes, and autoantibodies to nuclear antigens than did untreated mice or mice given NZBW HSCs. NZBW mice with established lupus-like disease that received nonmyeloablative conditioning and transplants of (MHC) haplomismatched allogeneic HSCs also had greatly increased overall survival. Mice that received transplants exhibited stabilization or reversal of their lupus symptoms; stabilized or decreased proteinuria, and a lower frequency of elevated circulating immune complexes or autoantibodies than did control mice. Induction of durable mixed chimerism by transplantation of purified allogeneic HSCs after nonmyeloablative conditioning has the potential to reverse symptoms of established NZBW lupus.     

Prognostic impact of elevated pretransplantation serum ferritin in patients undergoing myeloablative stem cell transplantation

Iron overload could be a significant contributor to treatment-related mortality (TRM) for patients with hematologic malignancies undergoing hematopoietic stem cell transplantation (HSCT). We studied 590 patients who underwent myeloablative allogeneic HSCT at our institution, and on whom a pretransplantation serum ferritin was available. An elevated pretransplantation serum ferritin level was strongly associated with lower overall and disease-free survival. Subgroup multivariable analyses demonstrated that this association was restricted to patients with acute leukemia or myelodysplastic syndrome (MDS); in the latter group, the inferior survival was attributable to a significant increase in TRM. There was also a trend toward an increased risk of veno-occlusive disease in patients with high ferritin. Our results argue that iron overload plays an important role in transplantation outcome for patients with acute leukemia or MDS, as it does in thalassemia. They also suggest future prospective trials to examine the potential benefit of chelation therapy in this setting.     

Critical review on non-myeloablative stem cell transplantation (NST)

Allogeneic stem cell transplantation is an established treatment modality for a variety of hematologic malignancies. Unfortunately, it carries a high risk of complications and toxicities related to the intensive preparative regimen which is traditionally used for pre-transplant myeloablation and the graft versus host disease, which may be life threatening. Thus allogeneic stem cell transplantation has been used only for younger patients with a good performance status, excluding many other potential candidates due to advanced age or comorbid conditions. Using reduced intensity preparative regimens for allogeneic stem cell transplantation (non-myeloablative stem cell transplantation (NST)) researchers attempted to overcome these barriers in patients' selection and tried to make hematopoietic stem cell (HSC) transplantation a safer procedure. The well-described graft versus malignancy effect would be the most curative element in this treatment. After more than 5 years of cumulative clinical experience, we know that NST is a feasible treatment option for patients with suboptimal performance status and is mostly effective in slow proliferating malignancies, which gives time for a graft versus malignancy effect to take place. Additionally achievement of stable donor cell engraftment with NSTs provides a platform for adoptive immune cell treatments and is promising for extended indications of stem cell transplantation in the future.