Representativeness of systemic sclerosis patients in interventional randomized trials: an analysis of the EUSTAR database

Objective To estimate the extent of and the reasons for ineligibility in randomized controlled trials (RCTs) of SSc patients included in the EUSTAR database, and to determine the association between patient's features and generalizability of study results. Methods We searched Clinicaltrials.gov for all records on interventional SSc-RCTs registered from January 2013 to January 2018. Two reviewers selected studies, and information on the main trial features were retrieved. Data from 8046 patients having a visit in the EUSTAR database since 2013 were used to check patient's eligibility. The proportion of potentially eligible patients per trial, and the risk factors for ineligibility were analysed. Complete-, worst- and best-case analyses were performed. Results Of the 37 RCTs included, 43% were conducted in Europe, 35% were industry-funded, and 87% investigated pharmacological treatments. Ninety-one percent of 8046 patients included could have participated in at least one RCT. In complete-case analysis, the median [range] proportion of eligible patients having the main organ complication targeted by each study was 60% [10-100] in the overall sample of trials, ranging from 50% [32-79] for trials on skin fibrosis to 90% [34-77] for those targeting RP. Among the criteria checked, treatment- and safety-related but not demographic were the main barriers to patient's recruitment. Older age, absence of RP, and lower mRSS were independently associated with the failure to fulfill criteria for any of the included studies. Conclusions Patient's representativeness in SSc-RCTs is highly variable and is driven more by treatment- and safety-related rather than demographic criteria.