BACKGROUND: To better understand the available clinical effectiveness data in eosinophilic granulomatosis with polyangiitis (EGPA), a systematic literature review was undertaken. The primary objective of this review was to collect randomised controlled trial (RCT) data on the efficacy, impact on quality of life, safety, and tolerability of all available treatments for EGPA. Secondary objectives were to collect similar endpoint data in observational-study or single-arm trials.
METHODS: The review was undertaken to meet the requirements of the National Institute for Health and Care Excellence (NICE), the Centre for Reviews and Dissemination's Guidance for Undertaking Reviews in Health Care, the Cochrane Collaboration and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting methods. Searches were conducted in electronic databases (PubMed, Embase, Cochrane and BIOSIS); conference abstracts (EULAR; ACR), and trial registry sites. Searches were not limited by date, language, or geographical location. The quality assessment of each RCT was performed to standards recommended by NICE and Cochrane guidance. The quality assessment of each observational study was performed using the Critical Appraisal Skills Programme (CASP) Cohort Study or Case-Control Study checklists.
RESULTS: A total of 1,063 records were selected for manual screening. After the initial screening of titles/abstracts, 217 publications were progressed for further screening. 57 articles were included after the second screening, and an additional data-on-file article was added. The review identified five RCTs that assessed various treatments in EGPA (e.g. mepolizumab, prednisone, immunosuppressants). Most RCTs included a small sample of patients (n=30-136); therefore, the conclusions derived regarding the efficacy and safety of the treatments are limited. Twenty-one prospective studies were included with seven different comparators treatments. Generally, the treatments identified in the prospective studies were effective in inducing remission, reducing relapse rates, and reducing corticosteroid use in patients with EGPA, but maintenance treatments were limited in their efficacy. In many of the studies, there was no comparative arm and low numbers of patients with EGPA (n=3-118), and the outcomes reported were not consistent, making it hard to draw definitive conclusions on the effectiveness of many of the therapies for EGPA. Of the 30 retrospective studies that assessed treatments in EGPA, 26 were single-arm. Most patients received other medications in combination with the treatments of interest, and as there was no control arm in all but three studies, the interpretation of outcomes is limited.
CONCLUSIONS: The clinical evidence for treatments of EGPA is sparse with many trial featuring small sample sizes, inconsistent reporting of outcomes, open trial designs, or lack of comparators. Additional RCTs would be beneficial to further evaluate treatment efficacy in patients with EGPA, particularly in relation to outcomes such as symptom scores, steroid sparing, and HRQOL due to the minimal amount of data available from the included RCTs.
