title: Exogenous estrogen and the risk of biliary tract cancer - a population-based study in a cohort of Swedish men treated for prostate cancer.
abstract: BACKGROUND
  To assess the role of exogenous estrogen in the etiology of biliary tract cancer, a nationwide population-based cohort study in Sweden was performed.
  
  
  METHODS
  The study included all men in Sweden with prostate cancer diagnosed in 1961-2008. Due to treatment standards, patients diagnosed in 1961-1980 were considered more exposed to estrogen, while those diagnosed in 1981-2008 were regarded less exposed. Standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) were calculated to estimate the risk of biliary tract cancer in cohort members compared to the corresponding Swedish male population.
  
  
  RESULTS
  After 849 307 person-years of follow-up in 203 131 prostate cancer patients, there were 41 incident gallbladder cancers and 36 cancers of the extra-hepatic bile ducts. In overall, there were no apparent differences in the risk of gallbladder cancer or bile duct cancer between patients diagnosed in 1961-1980 and patients diagnosed in 1981-2008. However, in patients diagnosed in 1961-1980, there was a statistically non-significant increased risk of gallbladder cancer (SIR 1.34; 95% CI 0.71-2.29) and extra-hepatic bile duct cancer (SIR 1.20; 95% CI 0.55-2.28) > 5 years of follow-up after the prostate cancer diagnosis. No such association was found for patients diagnosed in 1981-2008. Sensitivity analyses excluding prostate cancer patients exposed to potential confounding factors did not change the SIRs.
  
  
  CONCLUSIONS
  Long exposure to high doses of exogenous estrogen might increase the risk of biliary tract cancer. However, any potential excess risk of bile duct cancer resulted by prolonged exposure to high doses of exogenous estrogen seems to be small.
authors.affiliation: a Department of Molecular Medicine and Surgery , Karolinska Institutet , Stockholm , Sweden ;
authors.forename: Carl
authors.initials: C
authors.lastname: Kilander
authors.affiliation: a Department of Molecular Medicine and Surgery , Karolinska Institutet , Stockholm , Sweden ;
authors.forename: Fredrik
authors.initials: F
authors.lastname: Mattsson
authors.affiliation: a Department of Molecular Medicine and Surgery , Karolinska Institutet , Stockholm , Sweden ;
authors.forename: Yunxia
authors.initials: Y
authors.lastname: Lu
authors.affiliation: b Unit of Epidemiology, Institute of Environmental Medicine, Karolinska Institutet , Stockholm , Sweden ;
authors.forename: Rickard
authors.initials: R
authors.lastname: Ljung
authors.affiliation: a Department of Molecular Medicine and Surgery , Karolinska Institutet , Stockholm , Sweden ;|c Division of Cancer Studies , Kings' College London , London , UK ;
authors.forename: Jesper
authors.initials: J
authors.lastname: Lagergren
authors.affiliation: b Unit of Epidemiology, Institute of Environmental Medicine, Karolinska Institutet , Stockholm , Sweden ;|d Department of Surgery , Eskilstuna County Hospital , Eskilstuna , Sweden ;|e Centre for Clinical Research Sörmland, Uppsala University , Eskilstuna , Sweden.
authors.forename: Omid
authors.initials: O
authors.lastname: Sadr-Azodi
mesh_terms: D000230:Adenocarcinoma / Q000628:therapy*; D000368:Aged; D000369:Aged, 80 and over; D001661:Biliary Tract Neoplasms / Q000139:chemically induced / Q000453:epidemiology* / Q000209:etiology; D015331:Cohort Studies; D004967:Estrogens / Q000009:adverse effects / Q000627:therapeutic use*; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000628:therapy*; D012189:Retrospective Studies; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology
chemical_list: D004967:Estrogens