The association between biliary tract cancers and cancers of other sites.

Abstract

Cancers of the biliary tract, including cancers of the gallbladder and bile duct, generally carry a very poor prognosis. Little is known about their etiology. The pattern of co-occurrence of two cancers may give clues to shared etiological risk factors. We therefore investigated the association of biliary tract cancer with other cancers, especially with estrogen- and tobacco-related cancers. We used data from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute. Associations between biliary tract cancer and other cancers were evaluated using the standardized incidence ratio as an estimate of the relative risk of a second primary malignancy. Estrogen-related cancers of the breast and uterine corpus and smoking-related upper aerodigestive tract cancers were not associated with biliary tract cancer. The risk of gallbladder cancer was inversely related to the risk of prostate cancer in men, but positively related to the risk of cervical cancer in women. This study suggests that smoking and estrogen exposure have minimal roles in the pathogenesis of biliary tract cancer. Our finding of an inverse relationship between prostate cancer and gallbladder cancer requires confirmation by further studies.