Regional variations in bladder cancer (BC) clinical trial availability within the United States (US).

Abstract

652 Background: Geographic disparities of phase I-III cancer clinical trials in the US are well described (Gu et al., JMCP 2024), but specific patterns for BC remain unexplored. We evaluated BC trial availability across US counties, interrogating associations with epidemiologic and socioeconomic factors. Methods: We queried ClinicalTrials.gov for adult, interventional BC trials from June 1, 2019 to June 1, 2025, and mapped the US site ZIP codes to counties using US Postal Service data. County-level age-adjusted incidence and mortality, and Social Vulnerability Index (SVI) were obtained from the CDC, NCI, and Agency for Toxic Substances and Disease Registry. The SVI reflects 16 socioeconomic and demographic variables. Trial characteristics were summarized descriptively. To assess geographic factors linked to trial availability, we modeled the number of trials available per county using a zero-inflated negative binomial (ZINB) regression—a model that accounts for the many counties without trials and estimates how county characteristics relate to the trial rate. The model was adjusted for county size, effectively analyzing the rate of trials per household. Results are expressed as incidence rate ratios (IRRs), where IRR > 1 indicates a higher trial rate as the predictor increases. Analyses used R 4.4.3. Results: We identified 436 eligible trials with active sites across 713 US counties; 77.3% of counties had no trials. Trials were mostly sponsored by pharmaceutical companies (48.4%) followed by academia (39%). Most trials focused on drug therapy (80.2%) over surgery (6.4%) or radiation (4.6%); and most were early phase (I/II, 72%). Using the ZINB model, higher BC incidence was associated with slightly higher trial rate per household (IRR 1.033, 95% CI 1.003–1.063). Notably, higher BC mortality was associated with fewer trials (IRR 0.80, 95% CI 0.73–0.88). Compared with high-SVI (most socially vulnerable) counties, less vulnerable counties had higher trial rates: lower-middle SVI (IRR 1.57, 95% CI 1.18–2.08), middle-high SVI (IRR 1.60, 95% CI 1.22–2.11), and low-SVI counties (IRR 2.53, 95% CI 1.89–3.38). Of 7,091 trial sites in the US, 657 (9.3%) were in counties with the highest quintile (Q5) for BC incidence. However, only 225 (3.2%) sites were in Q5 counties for BC mortality. Metastatic and non-metastatic trials were similarly represented across mortality quintiles. While most trials were early phase overall, high mortality counties had proportionally less early phase trial sites (56.4% Q5 vs. 63.8% Q1). Conclusions: Most US counties lacked a BC trial. Trial availability was higher where disease is diagnosed, not where patients most often die from it. Research access is concentrated in counties with high BC incidence and low social vulnerability. Expanding trial sites to high mortality or high-SVI counties may be an actionable step for investigators to improve equitable trial access nationwide.