The population-based incidence and mortality of biliary tract cancer in Sweden

Background: The incidence trends of biliary tract cancer need to be established. This study investigated the incidence and mortality of biliary tract cancer in Sweden in 1970-2010. Methods: Sex-specific biliary tract cancer incidence and mortality rates were evaluated using data from the Swedish Cancer Register, Patient Register and Causes of Death Register. Case registration was separate for each register. Gallbladder cancer and cancers of the extra-hepatic bile ducts were analyzed separately. Standardized incidence rates were calculated and joinpoint regression was used to calculate annual percent changes (APC) with 95% Confidence Intervals (CIs). Results: The incidence of non-gallbladder extra-hepatic cancers assessed from the Cancer Register decreased in men and women from the mid 1980's (APC: -4.0, 95% CI -5.3 - -2.7 and APC -6.3, 95% CI -7.7 - -4.8, respectively), whereas the mortality of non-gallbladder extra-hepatic cancers rather increased until 1990 (APC: 2.1, 95% CI 1.4-2.8 and APC 2.7, 95% CI 1.3-4.1, in men and women respectively). Notably, the mortality rate was greater than the incidence rate as assessed from the Cancer Register from the early 1990's and onwards. The incidence of non-gallbladder extra-hepatic cancers derived from the Patient Register also increased over time. Gallbladder cancer incidence and mortality rates generally decreased. However, incidence rates assessed from the Patient Register decreased to a lesser extent. Conclusions: The incidence of gallbladder cancer seems to have decreased over the past decades in Sweden. The incidence trends for extra-hepatic tumors other than gallbladder cancer may however be obscured by under-reporting.