Objectives. To estimate the average time to complete patient enrollment and identify factors associated with accrual rates in systemic sclerosis (SSc) randomized controlled trials (RCTs). Methods. We searched published SSc-RCTs indexed in PubMed from 2000 to 2024, selecting those with recruitment completed before the COVID-19 pandemic. We recorded key trial features (country, phase, randomization ratio, intervention, blinding, funding source, outcome type) and enrollment year(s). We measured enrollment duration and accrual rate (participants per month). A multivariable negative binomial generalized linear model was used to identify factors associated with accrual rate. Results. We included 80 studies, mostly single-country (75.0%) and industry-funded (57.5%), with recruitment concentrated in Europe (36.2%) and North America (22.5%). In 65% of studies, both limited and diffuse SSc patients were enrolled. The median sample size was 40.5 patients, with 20% of RCTs enrolling more than 100 patients. The median recruitment time was 15 months (IQR 9.9-30.0), with a median accrual rate of 3.1 (IQR 1.6-5.5) participants per month. Recruitment rates varied over time, with faster accrual early in the 2000s and after 2012, and a slower period in between. Multivariable analysis showed that accrual rate was positively associated with skewed randomization, non-industry funding, international recruitment, and inclusion of both SSc subsets, especially compared to studies involving only dcSSc patients. Conclusions. Recruiting SSc patients for RCTs has been challenging, with generally slow accrual over the past 20 years and no significant improvement over time.

MI has received speaking fees from Boehringer Ingelheim and Vifor. The other authors do not declare any conflict of interest.

This study did not receive any funding

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

All data produced in the present study are available upon reasonable request to the authors