Majority of people, minority of places: The people–place gap in US biliary tract cancer trial access across social vulnerability strata.

Abstract

486 Background: Biliary tract cancers (BTC) are uncommon malignancies with poor outcomes. Clinical trial access is central to equity yet may be shaped by geography and social determinants of health (SDOH). In this study, we applied a people–place coverage framework to measure U.S. access to BTC trials and to evaluate SDOH differences with the county Social Vulnerability Index (SVI). Methods: We performed observational, geospatial analysis of public registries. We used ClinicalTrials.gov for U.S. interventional BTC trials with active recruitment and compiled unique site locations annually (2010–2022). Sites were standardized at facility–city–state level and assigned coordinates via ZIP/city centroids. Counties were represented by Census centroids and linked to 2010–2022 populations and CDC/ATSDR SVI 2020 (quintiles Q1 least to Q5 most vulnerable). Coverage was residence ≤50 miles (primary) or ≤100 miles (secondary) from ≥1 active site (Haversine). End points were national population-weighted coverage, county-weighted coverage and SVI equity gaps (Q5 vs Q1) for both weightings. Sensitivity analyses excluded “Not yet recruiting” and restricted to Phase 2–3 trials. Missing site locations without U.S. city/ZIP were excluded. Analyses were conducted on de-identified, aggregate public data. Results: After 2018 active BTC trial availability expanded , reaching 195 U.S. sites by 2022. In 2022, 50mile population coverage was 59.0%, yet only 18.9% of counties were covered a 40.1% people–place gap (access inequality ratio 3.1). From 2016–2020 showed higher coverage in least-vulnerable (SVI Q1) vs most-vulnerable (Q5) counties (+4.1 to +8.8 points). In 2022, population-weighted coverage showed an equity reversal with higher coverage among SVI Q5, reflecting gains in dense, high-SVI metropolitan areas; however, county-weighted estimates still showed lower coverage for vulnerable/rural counties (+6.4 point shortfall). Patterns were similar at 100 miles threshold and robust in sensitivity analyses, excluding “Not yet recruiting” sites and restricting to Phase 2-3 trials. Conclusions: BTC trials now reach a majority of people but a few places, revealing persistent urban–rural and SDOH-linked inequities. Our people–place approach clarifies how population level equity can improve while geographic inequity persists. Closing this gap will require targeted rural site seeding, decentralized/tele-enabled elements, and travel/logistics support are warranted to extend BTC trial access beyond metropolitan centers. Year-wise BTC trial access and equity summary. Year Sites Pop 50mi % County 50mi % County 100mi % SVI Gap (Pop) SVI Gap (County) 2010 0 0.0 0.0 0.0 +0.0 pp +0.0 pp 2014 0 0.0 0.0 0.0 +0.0 pp +0.0 pp 2016 2 3.4 0.8 3.0 +4.1 pp +1.0 pp 2018 3 5.4 1.1 4.0 +4.3 pp +1.3 pp 2020 51 33.7 8.4 23.5 +8.8 pp +10.5 pp 2022 195 59.0 18.9 48.7 −5.4 pp +6.4 pp