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Background: Biliary tract cancer (BTC) often goes undetected until its advanced stages, resulting in a poor prognosis. Given the anatomical closeness of the gallbladder and bile ducts to the pancreas, the inflammatory processes triggered by acute pancreatitis might increase the risk of BTC.

Objective: To assess the association between acute pancreatitis and the risk of BTC.

Methods: Using the Swedish Pancreatitis Cohort (SwePan), we compared the BTC risk in patients with a first-time episode of acute pancreatitis during 1990–2018 to a 1:10 matched pancreatitis-free control group. Multivariable Cox regression models, stratified by follow-up duration, were used to calculate hazard ratios (HRs), adjusting for socioeconomic factors, alcohol use, and comorbidities.

Results: BTC developed in 0.94% of 85,027 acute pancreatitis patients and in 0.23% of 814,993 controls. The BTC risk notably increased within 3 months of hospital discharge (HR 82.63; 95% CI: 63.07–108.26) and remained elevated beyond 10 years of follow-up (HR 1.82; 95% CI: 1.35–2.47). However, the long-term risk of BTC subtypes did not increase with anatomical proximity to the pancreas, with a null association for gallbladder and extrahepatic tumors. Importantly, patients with acute pancreatitis had a higher occurrence of early-stage BTC within 2 years of hospital discharge than controls (13.0 vs. 3.6%; p-value <0.01).

Conclusion: Our nationwide study found an elevated BTC risk in acute pancreatitis patients; however, the risk estimates for BTC subtypes were inconsistent, thereby questioning the causality of the association. Importantly, the amplified detection of early-stage BTC within 2 years after a diagnosis of acute pancreatitis underscores the necessity for proactive BTC surveillance in these patients.