Aspirin Use and Risk of Biliary Tract Cancer: A Population-Based Study in Shanghai, China

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Abstract
The association of gallbladder and bile duct cancers with gallstones, cholecystitis, and cholangitis suggest that chronic inflammation contributes to the carcinogenic process. However, the effect of nonsteroidal anti-inflammatory drugs, such as aspirin, on biliary tract cancer has not been well studied. In a population-based case-control study conducted in Shanghai, China, we examined the relationship between aspirin use and the risk of biliary disease. A total of 627 patients with biliary tract cancer, including cancers of the gallbladder (n = 368), extrahepatic bile duct (n = 191), and ampulla of Vater (n = 68); 1,037 patients with biliary stones; and 958 healthy adults were included in the study. Self-reported data on aspirin use was collected from study participants by in-person interview. The prevalence of aspirin use was low, with 5.7% of the population controls being regular users. After controlling for age, sex, education, and biliary stone status, aspirin use was associated with a reduced risk of gallbladder cancer [odds ratio (OR), 0.37; 95% confidence interval (CI), 0.17-0.88]. An inverse relationship was also observed for frequency and duration of use and with younger age when starting use. In addition, there was a nonsignificant reduction in the risk of bile duct (OR, 0.48; 95% CI, 0.19-1.19) and ampullary cancers (OR, 0.22; 95% CI, 0.03-1.65) associated with aspirin use, whereas no clear association was seen with biliary stones (OR, 0.92; 95% CI, 0.59-1.44). Further studies of biliary tract cancer in other populations are needed to confirm these results and to elucidate the mechanisms that underlie the reduced risk associated with use of aspirin and possibly other nonsteroidal anti-inflammatory drugs.