Current Status of Allogeneic Hematopoietic Stem Cell Transplantation for Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal nocturnal hemoglobinuria: Where we stand

For the last 20 years, therapy of paroxysmal nocturnal hemoglobinuria (PNH) relied-up until recently-on antibody based terminal complement inhibitionon. PNH pathophysiology-a mutational defect leading to partial or complete absence of complement-regulatory proteins on blood cells-leads to intravascular hemolysis and consequences such as thrombosis and other sequelae. A plethora of new drugs interfering with the proximal and terminal complement cascade are under recent development and the first "proof-of-pinciple" proximal complement inhibitor targeting C3 has been approved in 2021. "PNH: where we stand" will try to give a brief account on where we came from and where we stand focusing on approved therapeutic options. The associated improvements as well as potential consequences of actual and future treatments as well as their impact on the disease will continue to necessitate academic and scientific focus on improving treatment options as well as on side effects and outcomes relevant to individual patient lives and circumstances in order to develop effective, safe, and available treatment for all hemolytic PNH patients globally.

The spectrum of paroxysmal nocturnal hemoglobinuria clinical presentation in a Brazilian single referral center

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematological disorder caused by the expansion of a hematopoietic clone harboring a somatic genetic variant in the PIG-A gene translating into a wide spectrum of clinical and laboratory changes, from intravascular hemolysis, thrombosis, and bone marrow failure to subclinical presentation. In this study, we retrospectively analyzed 87 consecutive cases (39 women; median follow-up, 18 months; range, 0–151 months) in whom a PNH clone was detected by flow cytometry between 2006 and 2019 seen at a single Brazilian referral center. The median age at diagnosis was 29 years (range, 8 to 83 years); 29 patients (33%) were initially classified as PNH/bone marrow failure, 13 (15%) as classic PNH, and 45 (52%) as subclinical PNH. The median overall survival (OS) of the entire cohort was not reached during follow-up, without significant differences between groups. At diagnosis, the median PNH clone size was 2.8% (range, 0 to 65%) in erythrocytes and 5.4% (range, 0 to 80%) in neutrophils. Fourteen patients experienced clone expansion during follow-up; in other 14 patients the clone disappeared, and in 18 patients it remained stable throughout the follow-up. A subclinical PNH clone was detected in three telomeropathy patients at diagnosis, but it was persistent and confirmed by DNA sequencing in only one case. In conclusion, PNH presentation was variable, and most patients had subclinical disease or associated with marrow failure and did not require specific anticomplement therapy. Clone size was stable or even disappeared in most cases.

Hematopoietic Stem Cell Transplantation for Patients with Paroxysmal Nocturnal Hemoglobinuria with or without Aplastic Anemia: A Multicenter Turkish Experience

Objective:

Although inhibition of the complement system at different steps is a promising therapy modality in patients with paroxysmal nocturnal hemoglobinuria (PNH), allogeneic hematopoietic stem cell transplantation (HCT) is still the only curative therapy, especially for patients with intractable hemolysis or bone marrow failure. The aim of this study is to evaluate the outcomes of allogeneic HCT in PNH patients with aplastic anemia (PNH-AA) or without.

Materials and Methods:

Thirty-five PNH/PNH-AA patients who were treated with allogeneic HCT in 10 transplantation centers in Turkey were retrospectively analyzed.

Results:

Sixteen (45.7%) and 19 (54.3%) patients were diagnosed with classical PNH and PNH-AA, respectively. The median age of the patients was 32 (18-51) years. The 2-year overall survival (OS) rate and rate of graft-versus-host disease-free, failure-free survival (GFFS) was 81.2% and 78.1%, respectively. The 2-year OS in cases of classical PNH and PNH-AA was 81.3% and 79.9%, respectively (p=0.87), and 2-year GFFS in cases of PNH and PNH-AA was 79% and 76% (p=0.977), without statistical significance. The OS and GFFS rates also did not differ between transplantations with matched sibling donors (MSDs) and matched unrelated donors (MUDs).

Conclusion:

Allogeneic HCT with MSDs or MUDs is a good option for selected patients with classical PNH and PNH-AA. In particular, patients with debilitating and refractory hemolysis and patients with bone marrow failure might form an excellent group of candidates for allogeneic HCT.

Circulating Endothelial Progenitor Cells and Their Relation to Thrombosis in Paroxysmal Nocturnal Hemoglobinuria and Aplastic Anemia

Thrombosis is a leading cause of morbidity and mortality in paroxysmal nocturnal hemoglobinuria (PNH). Multiple factors are responsible for the thrombotic tendency in these patients. Endothelial progenitorcells (EPCs) originate from primitive hematopoietic stem cells. The EPC count is considered indicative of potential damage and restoration capacity in vascular disease; lower EPC counts are deemed as a risk factor in cardiovascular diseases. We aimed to investigate the count of circulating EPCs in PNH and aplastic anemia (AA) patients receiving eculizumab treatment or not receiving treatment and their relationship with thrombosis. Seventeen PNH patients, 18 AA patients, and 10 healthy volunteers were included in the study. The CD309, CD133, and CD34 antibodies were used to determine counts of circulating EPCs using flowcytometry. EPC levels were compared between the PNH, AA, and healthy control groups. Kolmogorov-Smirnov test. ANOVA, Kruskal-Wallis, and Mann-Whitney U testswereperformedto analyze the quantitative data, while χ2 testing was performed to analyze the qualitative data. Therewasnosignificantdifference in EPC levelsbetweenpatientswithandwithout a history of thrombosis (P > 0.05). Further, therewasnosignificantdifference in thelevels of EPCsbetweenthe AA and PNH groups (P  > 0.05). However, there was a significant positive correlation between levels of EPCs and lactate dehydrogenase (LDH) in multivariate analysis (P < 0.05). The study findings suggest that hemolysis promotes vascular endothelial and new blood vessel formation. Increased EPCs in PNH may indirectly indicatevascular endothelial damage in PNH.

Anti-complement Treatment for Paroxysmal Nocturnal Hemoglobinuria: Time for Proximal Complement Inhibition? A Position Paper From the SAAWP of the EBMT

The treatment of paroxysmal nocturnal hemoglobinuria has been revolutionized by the introduction of the anti-C5 agent eculizumab; however, eculizumab is not the cure for Paroxysmal nocturnal hemoglobinuria (PNH), and room for improvement remains. Indeed, the hematological benefit during eculizumab treatment for PNH is very heterogeneous among patients, and different response categories can be identified. Complete normalization of hemoglobin (complete and major hematological response), is seen in no more than one third of patients, while the remaining continue to experience some degree of anemia (good and partial hematological responses), in some cases requiring regular red blood cell transfusions (minor hematological response). Different factors contribute to residual anemia during eculizumab treatment: underlying bone marrow dysfunction, residual intravascular hemolysis and the emergence of C3-mediated extravascular hemolysis. These two latter pathogenic mechanisms are the target of novel strategies of anti-complement treatments, which can be split into terminal and proximal complement inhibitors. Many novel terminal complement inhibitors are now in clinical development: they all target C5 (as eculizumab), potentially paralleling the efficacy and safety profile of eculizumab. Possible advantages over eculizumab are long-lasting activity and subcutaneous self-administration. However, novel anti-C5 agents do not improve hematological response to eculizumab, even if some seem associated with a lower risk of breakthrough hemolysis caused by pharmacokinetic reasons (it remains unclear whether more effective inhibition of C5 is possible and clinically beneficial). Indeed, proximal inhibitors are designed to interfere with early phases of complement activation, eventually preventing C3-mediated extravascular hemolysis in addition to intravascular hemolysis. At the moment there are three strategies of proximal complement inhibition: anti-C3 agents, anti-factor D agents and anti-factor B agents. These agents are available either subcutaneously or orally, and have been investigated in monotherapy or in association with eculizumab in PNH patients. Preliminary data clearly demonstrate that proximal complement inhibition is pharmacologically feasible and apparently safe, and may drastically improve the hematological response to complement inhibition in PNH. Indeed, we envision a new scenario of therapeutic complement inhibition, where proximal inhibitors (either anti-C3, anti-FD or anti-FB) may prove effective for the treatment of PNH, either in monotherapy or in combination with anti-C5 agents, eventually leading to drastic improvement of hematological response.

How we treat paroxysmal nocturnal hemoglobinuria: A consensus statement of the Canadian PNH Network and review of the national registry

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematologic disease characterized by intravascular hemolysis, thrombophilia, and marrow failure. Its phenotype is due to absent or reduced expression of GPI-linked complement regulators and subsequent sensitivity of hematopoietic cells to complement-mediated damage and lysis. Introduction of the terminal complement inhibitor eculizumab drastically improved outcomes in PNH patients; however, despite this improvement, there remain several challenges faced by PNH patients and physicians who care for them. One of the most important is increasing awareness of the heterogeneity with which patients can present, which can lead to significant delays in recognition. Data from the Canadian PNH Registry are presented to demonstrate the variety of presenting symptoms. In Canada, geography precludes consolidation of care to just a few centers, so management is distributed across academic hospitals, linked together as the Canadian PNH Network. The Network over the last several years has developed educational programs and clinical checklists and has worked to standardize access to diagnostics across the country. Herein, we address some of the common diagnostic and therapeutic challenges faced by PNH physicians and give our recommendations. Gaps in knowledge are also addressed, and where appropriate, consensus opinion is provided.

Successful reduced-intensity conditioning hematopoietic stem cell transplantation for paroxysmal nocturnal hemoglobinuria with aplastic anemia in two children

Paroxysmal nocturnal hemoglobinuria (PNH) is an extremely rare cause of bone marrow failure in children. We report two children who presented with pancytopenia, and were diagnosed with PNH with severe aplastic anemia. Both children underwent upfront, successful hematopoietic stem cell transplantation with reduced-intensity conditioning. One patient had a syngeneic donor, and one patient had a 10/10 matched unrelated donor. Neither patient developed graft versus host disease, infections, or recurrent PNH. Reduced-intensity conditioning hematopoietic stem cell transplantation is a reasonable therapy for PNH with marrow failure in children.

Development of a disease-specific quality of life questionnaire for patients with aplastic anemia and/or paroxysmal nocturnal hemoglobinuria (QLQ-AA/PNH)-report on phases I and II

Acquired aplastic anemia (AA) and paroxysmal nocturnal hemoglobinuria (PNH) are interrelated ultra-rare diseases. Quality of life (QoL) evaluation tools used in studies for AA and PNH are unspecific and designed for cancer patients (e.g., the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire, EORTC QLQ-C30). Given the complexity of AA and PNH, variation in symptoms and treatments, younger age of many patients, and the fact that AA and PNH are not classified as malignant diseases, it is likely that cancer-specific questionnaires are inappropriate. We generate an AA/PNH-specific QoL questionnaire (QLQ-AA/PNH), performed according to EORTC guidelines. QoL issues were obtained from the literature and interviews with patients and physicians (phase I), then ranked by patients and physicians. In phase II, items were created. Patients in more than 25 German and Swiss cities were interviewed face to face. In phase I, interviews of 19 patients and 8 physicians specialized in AA/PNH treatment resulted in 649 QoL issues; these were condensed to 175 and graded according to their importance by 30 patients and 14 physicians (phase II). Five physicians took part in phases I and II. Altogether, 97 issues were rated important. Twelve EORTC QLQ-C30 items were not rated important, while several new QoL aspects were brought up. Modifications in wording and phrasing led to two questionnaires with 77 items regarding general QoL aspects and 20 items regarding medical care. Important QoL aspects of PNH/AA patients are inappropriately captured with available QoL tools. Developing a new QoL questionnaire specific for this patient group is warranted.

Pathophysiology, diagnosis, and treatment of paroxysmal nocturnal hemoglobinuria: a review

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder of the hematopoietic stem cell that makes blood cells more sensitive to the action of complement. Patients experience intravascular hemolysis, smooth muscle dystonia, renal failure, arterial and pulmonary hypertension, recurrent infectious diseases and an increased risk of notably dreadful thrombotic complications. The diagnosis is made by flow cytometry. Efforts have been recently performed to improve the sensitivity and the standardization of this technique. PNH is frequently associated with aplastic anemia or low-risk myelodysplasia and may be asymptomatic. Management of the classical form of PNH has been dramatically revolutionized by the development of eculizumab, which brings benefits in terms of hemolysis, quality of life, renal function, thrombotic risk, and life expectancy. Prophylaxis and treatment of arterial and venous thrombosis currently remain a challenge in PNH.

Vaccine therapy for cytomegalovirus in the setting of allogeneic hematopoietic cell transplantation

Passive immunization against CMV is desirable to minimize or perhaps eliminate complications related to CMV disease. In allogeneic hematopoietic cell transplantation (allo-HCT), the major challenge facing a successful anti-CMV vaccine is inducing immunity in an immunocompromised host. To date, only one CMV vaccine, ASP0113, has been evaluated in a randomized, placebo-controlled Phase II study. ASP0113 is a bivalent product containing two plasmids that encode CMV glycoprotein B and tegument phosphoprotein 65, respectively. Although there was no significant difference in rate of initiation of anti-CMV therapy, rates of CMV viremia were lower in the ASP0113 group when measured by a central laboratory. Also, time-to-first episode of viremia was longer in subjects receiving ASP0113. These findings paved the way for an ongoing placebo-controlled Phase III study aiming at enrolling 500 subjects. Results of this Phase III trial, especially if it meets clinically meaningful endpoints, will ultimately determine the role of anti-CMV vaccine strategies in allo-HCT.

Eculizumab for treating patients with paroxysmal nocturnal hemoglobinuria

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is a chronic, not malignant, disease of the hematopoietic stem cells, associated with significant morbidity and mortality. It is a rare disease with an estimated incidence of 1.3 new cases per one million individuals per year. The treatment of PNH has been largely empirical and symptomatic, with blood transfusions, anticoagulation, and supplementation with folic acid or iron. Eculizumab, a biological agent that inhibits complement cascade, was developed for preventing hemolytic anemia and severe thrombotic episodes.

OBJECTIVES

To assess the clinical benefits and harms of eculizumab for treating patients with paroxysmal nocturnal hemoglobinuria (PNH).

SEARCH METHODS

We conducted a comprehensive search strategy. We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library 2014, Issue 5), Ovid MEDLINE (from 1946 to 15 May 2014), EMBASE (from 1980 to 25 June 2014), and LILACS (from 1982 to 25 June 2014). We did not apply any language restrictions.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) irrespective of their publication status or language. No limits were applied with respect to period of follow-up. We excluded quasi-RCTs. We included trials comparing eculizumab with placebo or best available therapy. We included any patient with a confirmed diagnosis of PNH. Primary outcome was overall survival.

DATA COLLECTION AND ANALYSIS

We independently performed a duplicate selection of eligible trials, risk of bias assessment, and data extraction. We estimated risk ratios (RRs) and 95% confidence interval (CIs) for dichotomous outcomes, and mean differences (MDs) and 95% CIs for continuous outcomes. We used a random-effects model for analysis.

MAIN RESULTS

We identified one multicenter (34 sites) phase III RCT involving 87 participants. The trial compared eculizumab versus placebo, and was conducted in the US, Canada, Europe, and Australia with 26 weeks of follow-up. This small trial had high risk of bias in many domains (attrition and selective reporting). It was sponsored by a pharmaceutical company. No patients died during the study. By using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (scores can range from 0 to 100, with higher scores on the global health status and functioning scales indicating improvement), the trial showed improvement in health-related quality of life in patients treated with eculizumab (mean difference (MD) 19.4, 95% CI 8.25 to 30.55; P = 0.0007; low quality of evidence). By using the Functional Assessment of Chronic Illness Therapy Fatigue instrument (scores can range from 0 to 52, with higher scores indicating improvement in fatigue), the trial showed a reduction in fatigue (MD 10.4, 95% CI 9.97 to 10.83; P = 0.00001; moderate quality of evidence) in the eculizumab group compared with placebo. Eculizumab compared with placebo showed a greater proportion of patients with transfusion independence: 51% (22/43) versus 0% (0/44); risk ratio (RR) 46.02, 95% CI 2.88 to 735.53; P = 0.007; moderate quality of evidence; and withdrawal for any reason: 4.7% (2/43) versus 22.72% (10/44); RR 0.20, 95% CI 0.05 to 0.88; P = 0.03; moderate quality of evidence. Due to the low rate of events observed, the included trial did not show any difference between eculizumab and placebo in terms of serious adverse events: 9.3% (4/43) versus 20.4% (9/44); RR 0.15, 95% CI 0.15 to 1.37; P = 0.16; low quality of evidence. We did not observe any difference between intervention and placebo for the most frequent adverse events. One participant receiving placebo showed an episode of thrombosis. The trial did not assess overall survival, transformation to myelodysplastic syndrome and acute myelogenous leukemia, or development or recurrence of aplastic anemia on treatment.

AUTHORS' CONCLUSIONS

This review has detected an absence of evidence for eculizumab compared with placebo for treating paroxysmal nocturnal hemoglobinuria (PNH), in terms of overall survival, nonfatal thrombotic events, transformation to myelodysplastic syndrome and acute myelogenous leukemia, and development and recurrence of aplastic anemia on treatment. Current evidence indicates that compared with placebo, eculizumab increases health-related quality of life and increases transfusion independence. During the execution of the included trial, no patients died. Furthermore, the intervention seems to reduce fatigue and withdrawals for any reason. The safety profile of eculizumab is unclear. These conclusions are based on one small trial with risk of attrition and selective reporting bias.Therefore, prescription of eculizumab for treating patients with PNH can neither be supported nor rejected, unless new evidence from a large high quality trial alters this conclusion. Therefore, we urge the reader to interpret the trial results with much caution. Future trials on this issue should be conducted according to the SPIRIT statement and reported according to the CONSORT statement by independent investigators, and using the Foundation of Patient-Centered Outcomes Research recommendations.

Efficacy and safety of eculizumab in children and adolescents with paroxysmal nocturnal hemoglobinuria

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is rare in children, but represents a similarly serious and chronic condition as in adults. Children with PNH frequently experience complications of chronic hemolysis, recurrent thrombosis, marrow failure, serious infections, abdominal pain, chronic fatigue, and decreased quality of life with reduced survival. The terminal complement inhibitor eculizumab is proven to be effective and safe in adults and approved by the FDA for treatment of PNH.

PROCEDURE

This 12-week, open-label, multi-center phase I/II study evaluated pharmacokinetics, pharmacodynamics, efficacy, and safety in seven children with PNH 11-17 years of age. Eculizumab was intravenously administered at 600 mg weekly for 4 weeks, 900 mg in week 5, and 900 mg every 2 weeks thereafter (http://clinicaltrials.gov NCT00867932).

RESULTS

Eculizumab therapy resulted in complete and sustained inhibition of hemolysis in all participants with a reduction of lactate dehydrogenase to normal levels. All hematological parameters stabilized. No definitive, study drug-related adverse events were observed. Only one severe SAE of hospitalization due to aplastic anemia occurred, which was not study drug-related.

CONCLUSION

Eculizumab appears to be a safe and effective therapy for children with PNH.

Rapid donor T-cell engraftment increases the risk of chronic graft-versus-host disease following salvage allogeneic peripheral blood hematopoietic cell transplantation for bone marrow failure syndromes

The risk of graft-rejection after allogeneic hematopoietic cell transplantation using conventional cyclophosphamide-based conditioning is increased in patients with bone marrow failure syndromes (BMFS) who are heavily transfused and often HLA-alloimmunized. Fifty-six patients with BMFS underwent fludarabine-based reduced-intensity conditioning and allogeneic peripheral blood progenitor cell (PBPC) transplantation at a single institution. The conditioning regimen consisted of intravenous cyclophosphamide, fludarabine, and equine antithymocyte globulin. Graft-versus-host disease (GVHD) prophylaxis included cyclosporine A alone or in combination with either mycophenolate mofetil or methotrexate. To reduce the risk of graft-rejection/failure, unmanipulated G-CSF mobilized PBPCs obtained from an HLA-identical or single HLA-antigen mismatched relative were transplanted rather than donor bone marrow. Despite a high prevalence of pretransplant HLA-alloimmunization (41%) and a heavy prior transfusion burden, graft-failure did not occur with all patients having sustained donor lympho-hematopoietic engraftment. The cumulative incidence of grade II-IV acute-GVHD and chronic-GVHD was 51.8% and 72%, respectively; with 87.1% surviving at a median follow-up of 4.5 years. A multivariate analysis showed pretransplant alloimmunization and rapid donor T-cell engraftment (≥95% donor by day 30) were both significantly (P < 0.05) associated with the development of chronic-GVHD (adjusted HR 2.13 and 2.99, respectively). These data show fludarabine-based PBPC transplantation overcomes the risk of graft-failure in patients with BMFS, although rapid donor T-cell engraftment associated with this approach appears to increase the risk of chronic-GVHD. (Clinicaltrials.gov identifier: NCT00003838).

Allogeneic stem cell transplantation in paroxysmal nocturnal hemoglobinuria

BACKGROUND

In the era of eculizumab, identifying patients with paroxysmal nocturnal hemoglobinuria who may benefit from allogeneic stem cell transplantation is challenging.

DESIGN AND METHODS

We describe the characteristics and overall survival of 211 patients transplanted for paroxysmal nocturnal hemoglobinuria in 83 EBMT centers from 1978 to 2007. Next, we conducted a comparison with a cohort of 402 non-transplanted patients with paroxysmal nocturnal hemoglobinuria diagnosed between 1950 and 2005 in 92 French centers. We compared the occurrence of complications (i.e. thromboembolism and aplastic anemia) using either an individual or a stratum-matching procedure.

RESULTS

After a median follow-up of 5 years, the 5-year overall survival rate ± standard error (%) was 68 ± 3 in the transplanted group (54 ± 7 in the case of thromboembolism, 69 ± 5 in the case of aplastic anemia without thromboembolism and 86 ± 6 in the case of recurrent hemolytic anemia without thromboembolism or aplastic anemia). Only thromboembolism as the indication for transplantation was associated with worse outcome (P=0.03). We identified 24 pairs of transplanted and non-transplanted patients with thromboembolism for the matched comparison, with worse overall survival for the transplanted patients (hazard ratio=10.0; 95% confidence interval, 1.3-78.1; P=0.007). This was confirmed by the global matching procedure (P=0.03). As regards aplastic anemia without thromboembolism, 30 pairs were identified for the matched comparison. It was not observed that transplanted patients had a significantly worse overall survival (hazard ratio=4.0; 95% confidence interval, 0.9-18.9; P=0.06). A global matching procedure was not feasible.

CONCLUSIONS

Allogeneic stem cell transplantation is probably not a suitable treatment option for life-threatening thromboembolism in paroxysmal nocturnal hemoglobinuria.

The pathophysiology of paroxysmal nocturnal hemoglobinuria and treatment with eculizumab

Paroxysmal nocturnal hemoglobinuria is a rare disorder of hemopoietic stem cells. Affected individuals have a triad of clinical associations – intravascular hemolysis, an increased risk of thromboembolism, and bone marrow failure. Most of the symptoms experienced in this disease occur due to the absence of complement regulatory proteins on the surface of the red blood cells. Complement activation is thus not checked and causes destruction of these cells. Eculizumab is a monoclonal antibody treatment which specifically binds to the complement protein C5, preventing its cleavage, and so halts the complement cascade and prevents the formation of the terminal complement proteins. Eculizumab prevents intravascular hemolysis, stabilizes hemoglobin levels, reduces or stops the need for blood transfusions, and improves fatigue and patient quality of life as well as reducing pulmonary hypertension, decreasing the risk of thrombosis and protecting against worsening renal function. It is not a curative therapy but has a great benefit on those with this rare debilitating condition.

Trends of hematopoietic stem cell transplantation in the third millennium

PURPOSE OF REVIEW

Hematopoietic stem cell transplantation (HSCT) has evolved into an accepted therapy for many congenital or acquired disorders of the hematopoietic system. It has seen major changes in indications and use of transplant techniques. HSCT is a high cost procedure and requires investments; information on trends is essential for patient counselling and healthcare planning.

RECENT FINDINGS

HSCT rates have increased worldwide. Increase is constant and predictable; the reasons therefore are manifold. Introduction of reduced intensity conditioning regimens has opened access to patients at older age and with comorbidities. Higher numbers of unrelated volunteer donors and cord blood products give access to HSCT for patients without family donors. For some well defined indications, HSCT has become the most cost efficient therapy in countries with limited resources. Use of HSCT is under discussion for nonhematopoietic indications, as is the use of nonhematopoietic stem cells for organ repair.

SUMMARY

HSCT is likely to continue to increase for currently established indications. Indications and technologies will vary between countries with limited or nonrestricted resources. The most cost effective approach might not be the same everywhere. Novel indications will emerge but time will be needed to confirm their benefit. Close observation of global trends will become an essential tool for healthcare agencies in order to provide the necessary infrastructure in time.

Hematopoietic stem cell transplantation for paroxysmal nocturnal hemoglobinuria: long-term results of a retrospective study on behalf of the Gruppo Italiano Trapianto Midollo Osseo (GITMO)

BACKGROUND

Paroxysmal nocturnal hemoglobinuria is an acquired clonal disorder of the hemopoietic stem cells for which the only curative treatment is allogeneic hematopoietic stem cell transplantation.

DESIGN AND METHODS

The aim of this retrospective study was to assess the long-term clinical and hematologic results in 26 paroxysmal nocturnal hemoglobinuria patients who received hematopoietic stem cell transplantation in Italy between 1988 and 2006. The patients were aged 22 to 60 years (median 32 years). Twenty-three donors were HLA-identical (22 siblings and one unrelated) and 3 were HLA-mismatched (2 related and one unrelated).

RESULTS

Fifteen patients received a myeloablative conditioning consisting of busulfan and cyclophosphamide (in all cases from identical donor) and 11 were given a reduced intensity conditioning (8 from identical donor and 3 from mismatched donor). The cumulative incidence of graft failure was 8% (4% primary and 4% secondary graft failure). Transplant-related mortality for all patients was 42% (26% and 63% for patients transplanted following myeloablative or reduced intensity conditioning, respectively). As of October 31, 2009, 15 patients (11 in the myeloablative conditioning group and 4 in the reduced intensity conditioning group) are alive with complete hematologic recovery and no evidence of paroxysmal nocturnal hemoglobinuria following a median follow-up of 131 months (range 30-240). The 10-year Kaplan-Meier probability of disease-free survival was 57% for all patients: 65% for 23 patients transplanted from identical donor and 73% for 15 patients transplanted with myeloablative conditioning. No thromboembolic event nor recurrence of the disease were reported following transplant.

CONCLUSIONS

The findings of this study confirm that most patients with paroxysmal nocturnal hemoglobinuria may be definitively cured with hematopoietic stem cell transplantation.