Biliary tract cancers: A large burden for little Rhode Island.

e22587 Background: Biliary tract cancers (BTCs) are a rare and aggressive group of malignancies characterized by rapid onset of treatment resistance and poor survival rates. Several known risk factors include: cholelithiasis, primary sclerosing cholangitis, liver flukes, tobacco and alcohol use, exposure to asbestos or 1,2-dichloropropane. Over half of all cases diagnosed in the United States have no identifiable cause. A deeper understanding of regional differences in environmental toxin exposures may provide new insights into disease etiology. Methods: Patient data were extracted from an established database for patients treated at Brown University Health between 2010 and 2023 (Brown University Health IRB: 2077055-2). Patients residing outside of Rhode Island at time of diagnosis were excluded. For each case of BTC, we extracted data on ZIP code at time of diagnosis and the number of industrial facilities, industry sector type, top three chemicals released, total releases (lbs), percentage released, and Risk Screening Environmental Indicators (RSEI) score per 1, 2, and 3-mile radii from the EPA Toxics Release Inventory based on RSEI model, version 2.3.12 (USEPA, 2023). Cluster analysis (R version 4.4.1) identified naturally occurring groups in the data. Change in annual incidence per 10,000 residents was estimated using generalized mixed effects modeling. Results: A total of 213 patients (median age: 69 years, males: 115) were included. 82% identified as Caucasian, 7.5% Black, and 4.7% Asian. 64% had current or prior tobacco use and 56% had current or prior alcohol use. A three-group clustering solution was selected: G1 – minimal toxin exposure, G2 – broad toxin exposure, G3 – high metal exposure. G1 averaged zero facilities within the first 2-mile radii and 1.1 facilities in the third mile (G2: 3.3 and 7.4; G3: 11.8 and 19.9, respectively). G1 was primarily exposed to chemicals including methanol, naphthalene, and xylene. G2 was broadly exposed to fabricated metals, plastics, rubber, and electrical equipment while G3 was disproportionately exposed to fabricated metals and petroleum products. G2 and G3 shared higher exposures of copper, nickel, antimony, and lead; G3 also had significantly greater chromium exposure (p < 0.05). G1 had the highest average prevalence of BTC risk ( p < 0.0001) but no significant change over time ( p = 0.1466). Both G2 and G3 showed significant increases over time (G2: p < 0.0001; G3: p = 0.0045). Conclusions: Though no singular environmental toxin risk factor was identified, increased BTC risk over time may be partly explained by higher exposures to fabricated metals. However, specific chemical-metal combinations cannot be determined. Future prospective analysis, inclusive of occupational and nutritional exposures, may help further elucidate differences between groups.