[MOL] Risks for Billiary Track Cancer [01867] Medicine On Line

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[MOL] Risks for Billiary Track Cancer

Billiary Tract

Joseph McLaughlin, Ph.D.*

Little is known about the etiology of biliary tract cancer, which includes cancers of the gallbladder and extrahepatic bile ducts. In general, these cancers are more common outside the United States in areas such as South America and Eastern and Central Europe (Whelan et al., 1990; Fraumeni and Kantor, 1982). Within the United States, American Indians and Hispanic Americans are at greater risk than the general population, particularly for gallbladder cancer (Diehl, 1980; Fraumeni and Kantor, 1982).

Gallbladder Cancer

Although rare, cancer of the gallbladder is more likely to occur among women than men. The incidence per 100,000 population, during the period 1975-1985, was 1.7 for white women and 0.9 for white men. Rates for whites and blacks were similar, but the rates for American Indians were highest (17.1 for men, 8.8 for women). Gallbladder cancer was also elevated among Hispanic Americans, with women having a rate of 7.3, and men, l.7. The incidence rate for gallbladder cancer in both sexes has declined slightly since the late 1960s, which may be due in part to the large number of cholecystectomies (surgery to remove the gallbladder) performed each year in the United States (Graves, 1991). Survivorship of patients with this cancer is poor, with less than 10 percent living more than five years after diagnosis.

Gallstones are by far the most important risk factor for gallbladder cancer. Stones are reported in 60 to 80 percent of patients with gallbladder cancer, although the cancer itself occurs in only a very small fraction of the millions of individuals with gallstones (Bennion and Grundy, 1978; Fraumeni and Kantor, 1982). American Indians and Hispanic Americans also have a high rate of gallstones. Presumably, controlling the formation of gallstones would reduce the number of individuals with gallbladder cancer. Factors related to stone formation are: increasing age, being a woman, increased number of children, ethnicity, obesity, use of estrogen-containing drugs, and high fat and caloric intake (Bennion and Grundy, 1978; Diehl, 1980). A recent study, however, did not find oral contraceptive users to be at increased risk for gallbladder cancer (WHO Collaborative Study, 1989). A few studies have linked occupational factors with gallbladder cancer, including employment in rubber and automobile plants, papermills, petroleum refineries, and clothing factories, but it is uncertain whether these associations are causal (Malker et al., 1986).

Other Biliary Tract Cancers

Extrahepatic bile duct cancer is the primary tumor included among "other biliary tract cancers." Men predominate in this uncommon cancer, with an incidence rate among whites of l.5 for men compared with l.0 for women. As with gallbladder cancer, there is little difference in occurrence between whites and blacks. American Indians, however, have higher rates (4.2 for men, 2.8 for women). Japanese- and Chinese-Americans also have higher rates than whites or blacks, but lower rates than American Indians. Incidence rates for other biliary tract cancers have not changed appreciably in the last 20 years. As with gallbladder cancer, patients survive poorly, with only about 10 percent still alive five years after diagnosis.

Aside from gallstones, which occur in about 30 percent of patients with extrahepatic bile duct tumors, risks factors are few (Fraumeni and Kantor, 1982; Yen et al., 1987). The male excess might suggest cigarette smoking as a factor, but the one study that examined this issue found no excess risk (Yen et al., 1987). Other possible risk factors include ulcerative colitis; infestation with liver flukes; use of methyldopa (an antihypertensive agent); exposure to asbestos; employment in aircraft, chemical, and rubber plants; and use of oral contraceptives (Yen et al., 1987; Malker et al., 1986). None of these associations, however, has been solidly confirmed by well-designed epidemiologic studies.

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