Geographic accessibility of recruiting clinical trials for rare and common gastrointestinal malignancies in the United States.

1540 Background: Gastrointestinal (GI) cancers account for substantial cancer mortality, with rare GI malignancies experiencing particularly poor outcomes and limited therapeutic options. Clinical trials are essential for treatment development; however, the geographic accessibility of disease-specific trials for rare GI cancers remains insufficiently characterized. Methods: We queried ClinicalTrials.gov to identify actively recruiting interventional disease-specific trials for GI cancers in the United States (accessed Jan 2026). Trials were classified as common (colorectal, pancreatic, hepatocellular, gastroesophageal) or rare (anal, appendiceal, small bowel adenocarcinoma, biliary tract) GI cancers. Trial sites were geocoded by ZIP code. Geographic accessibility was defined as the proportion of the U.S. population residing within 30 miles of a recruiting trial site; areas without a site within 30 miles were defined as clinical trial deserts. Urban–rural status and income quartiles were derived from census-based classifications. A 60-mile access definition was evaluated as a sensitivity analysis. Results: A total of 283 disease-specific GI cancer trials encompassing 1,322 unique U.S. trial site ZIP codes were included. More than 80% trials were early-phase (Phase I–II). Using a 30-mile access definition, overall population coverage was 83.6%, with lower coverage in rural versus urban populations (47.5% vs 90.9%) and in the lowest vs highest income quartiles (65.8% vs 98.0%). Common GI cancers had broad access, including colorectal cancer (80.2% population coverage) and pancreatic cancer (75.3%). In contrast, more than half of the population resided in a clinical trial desert for rare GI cancers (biliary tract = 55.2%, small bowel = 56.4, anal cancer= 80.8%, appendiceal 99.5%). Over 75% of rural residents resided in trial deserts for any rare GI cancer. Findings were consistent using a 60-mile access definition. Conclusions: Geographic accessibility remains a major barrier for disease-specific clinical trials of rare GI malignancies. This results in extensive clinical trial deserts and perpetuates existing disparities for rural and lower-income populations. These findings highlight structural gaps in trial availability and support the need for more geographically inclusive trial designs. Geographic access to disease-specific gastrointestinal cancer clinical trials. Cancer type Trials(N) Trial site ZIP (N) % Pop ≤30 mi %Pop in trial desert %Rural Pop in trial desert %Lowest income quartile in trial desert Common Colorectal 82 1,026 80.2 19.8 59.2 38.5 Pancreas 75 730 75.3 24.7 67.1 45.1 Gastroesophageal 46 684 71.9 28.1 69.1 49.8 Hepatocellular cancer 45 210 54.7 45.3 93.2 64.5 Rare Biliary tract cancer 28 109 44.8 55.2 95.1 70.3 Small bowel adenocarcinoma 2 419 43.6 56.4 77.5 67.2 Anal 5 19 19.2 80.8 99.1 86.6 Appendicular 1 1</