A mixed-methods evaluation of the quantitative and perceived impact of Brexit on UK oncology clinical trial initiation between 2011 and 2020

Introduction This study explored the perceived impact of Brexit on oncology clinical trial initiation in the UK, with comparative analysis against Spain and France, and evaluated potential impact on the UK's leadership position in clinical research. A mixed-methods approach was employed comprising: (1) analysis of oncology clinical trial registrations (2011–2020) using ClinicalTrials.gov for the UK, Spain, and France; (2) a stakeholder survey on Brexit-related impacts (n = 22); and (3) a systematic literature review (SLR) conducted in line with PRISMA guidelines using PubMed, Web of Science, Google Scholar, and Embase (2011–2021), with critical appraisal via CASP criteria.Discussion and Analysis Clinical trial volume in the UK declined from 2017, returning to 2011 levels; a trend not mirrored in Spain and only transiently observed in France. From survey results (n = 22), stakeholders acknowledged a negative impact on EU collaboration, highlighting the importance of Horizon Europe programme funding and the role of European Research Networks (ERNs). The SLR identified concerns about increased trial costs, regulatory burden, and reduced patient access to innovative treatments in the UK post-Brexit. Alignment between UK and EU clinical trial regulation was widely seen as essential. UK trial activity shows a marked post-Brexit decline compared to France and Spain. Stakeholder and literature data suggest this trend may affect the UK's access to clinical trials for patients. The negative perception of Brexit's impact on collaboration, funding, and regulatory coherence warrants further investigation and policy response.Conclusion The decline in UK clinical trial volume to pre-2011 levels poses a risk to patient access and the UK's status as a global leader in drug development. Sustained collaboration with the EU is viewed as vital for mitigating these effects and maintaining research competitiveness.