Eculizumab for treating patients with paroxysmal nocturnal hemoglobinuria

Review question
We reviewed the evidence about the effects of eculizumab for treating patients with paroxsymal nocturnal hemoglobinuria.

Background
Paroxysmal nocturnal hemoglobinuria is a disorder of the hematopoietic stem cells (a cell that can self renew and differentiate into one or more cell types). It is characterized by episodes of intravascular hemolysis (destruction of red blood cells), and chronic hemolytic anemia. The intravascular destruction of red blood cells involves clinical findings in gastrointestinal, cardiovascular, pulmonary, cerebral, and urogenital systems, as well as clotting disorders.

The treatment of paroxysmal nocturnal hemoglobinuria has been largely empirical and symptomatic, with packed red blood cell transfusions, anticoagulation, and supplementation with folic acid or iron. Many different pharmacological interventions that are used for treating this medical disorder are not standardized. Eculizumab is a newly available biological agent for preventing hemolytic anemia and severe clotting episodes.

Study characteristics
We identified one study that included a limited number of patients comparing eculizumab with placebo. The study was published in 2006, and was conducted in the US, Canada, Europe, and Australia with 26 weeks of follow-up.

Key results
No patients died during the performance of this single study. The study showed a moderate improvement in the quality of life in patients treated with eculizumab. In addition, eculizumab reduced fatigue and the number of patients that withdrew from the study for any reason. Eculizumab showed a higher proportion of patients with transfusion independence. There was no difference between eculizumab and placebo in terms of adverse events, probably due to the low rate of events observed during the study. The trial did not assess other relevant outcomes such as overall survival, transformation to myelodysplastic syndrome and acute myelogenous leukemia, or development or recurrence of aplastic anemia on treatment.

Quality of evidence
The confidence in the results is moderate to low. The study had limitations in its design and execution, and was sponsored by the manufacturer of the drug that was assessed. Moreover, the limited number of patients included in the study led to imprecise results. Larger studies should provide more information about the effect of eculizumab in patients with paroxsymal nocturnal hemoglobinuria.

This plain language summary is current as of May 2014.

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.

Read the full abstract...
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 strategy: 

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.

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