Age trends in biliary tract cancer incidence by anatomical subtype: A Swedish cohort study

Studies from Western countries suggest that early-onset biliary tract cancer, a rare malignancy originating from the bile ducts (cholangiocarcinoma) or gallbladder, is increasing. We performed a population-based cohort study to outline age trends in biliary tract cancer incidence in Sweden.All patients with biliary tract cancer, excluding non-biliary chiefly hepatocellular histopathology, recorded in the Swedish Cancer Register in year 1993-2019 and at age 20-84 were included. Analyses were stratified by anatomical subtype; intrahepatic, gallbladder, perihilar, distal, and not specified. We analyzed absolute incidence rates by calendar period (1993-2001, 2002-2010, and 2011-2019) and annual percentage change (APC) including 95% confidence intervals (CI) across 1993-2019 for all ages and stratified into younger (20-54 years) and older (55-84 years) patients.Among 14,083 patients with biliary tract cancer, 1377 (9.8%) were younger. Gallbladder cancer incidence decreased (APC -2.82, 95% CI: -3.18--2.46), while intrahepatic cholangiocarcinoma increased (APC 1.74, 95% CI: 1.30-2.18), and the latter surpassed gallbladder as the most common subtype during the study period. While both intrahepatic and perihilar cholangiocarcinoma increased in both age groups, the rise was most prominent in younger adults, APC 3.01, 95% CI: 1.84-4.20 and 3.93, 95% CI: 2.08-5.81, respectively.Intrahepatic and perihilar cholangiocarcinoma are increasing in Sweden and more so younger adults. Further studies are needed to elucidate the underlying reasons behind the observed trends.