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Urinary BladderDebra T. Silverman, Sc.D.* |
Bladder cancer is the fifth most common cancer in the
United States, where it is chiefly a disease of white men over age
65. For 1994, 51,200 new cases and 10,000 deaths were estimated
(Boring et al., 1994). The incidence of 32.3 cases per 100,000
population among white men is more than twice that found in
non-white men. There is little racial difference in incidence among
women, who develop bladder cancer about a fourth as often as men.
From 1973 to 1991, the overall incidence of bladder cancer increased 10 percent (Ries et al., 1994). There was, however, a 28 percent increase for black men and a 34 percent increase for black women. From the early 1960s, 5-year relative survival among patients with bladder cancer increased more than 50 percent to a level of 80 percent for whites and 60 percent for blacks. Internationally, the incidence of bladder cancer varies about 10-fold (Parkin et al., 1992). The disease occurs most often in Western Europe and North America and least often in Eastern Europe and several areas of Asia (Silverman et al., in press). The most important known risk factor for bladder cancer is cigarette smoking; cigarette smokers develop bladder cancer two to three times more often than nonsmokers (Silverman et al., in press). Risk increases with amount smoked (number of packs per day), with moderate to heavy smokers experiencing two to five times the risk of nonsmokers. Quitting smoking is associated with a 30 to 60 percent decrease in risk. Smoking is estimated to be responsible for about 48 percent of the bladder cancers among men and 32 percent among women in the United States. As early as 1895, workers in the dyestuffs industry showed a high risk of bladder cancer that was later associated with exposure to certain aromatic amines, a class of compounds used to make dyes (Silverman et al., 1992a). Two of these chemicals, benzidine and 2-naphthylamine, are now known to be potent bladder carcinogens in humans (Case, 1954). Workers in the rubber and leather industries also have an increased risk of developing bladder cancer. Occupations in which workers are suspected of having an elevated bladder cancer risk include painter, driver of trucks and other motor vehicles, aluminum worker, machinist, chemical worker, printer, metal worker, hairdresser, and textile worker (Silverman et al., in press). The possible risk of bladder cancer associated with widely used artificial sweeteners received much attention when the Food and Drug Administration removed cyclamates from the market in 1969. It was later reported that the sweetener saccharin caused bladder cancer in male laboratory rats when the animals were exposed to the chemicals before birth (Silverman et al., 1992a). But epidemiological studies show that, overall, people who use artificial sweeteners do not appear to have a higher incidence of bladder cancer than nonusers (Morrison and Buring, 1980; Hoover et al., 1980). Although some studies have indicated a possible link between bladder cancer and coffee drinking, other studies have found little or no increase in bladder cancer incidence among coffee drinkers compared with those who do not drink coffee (Silverman et al., in press). The inconsistency of these observations suggests that, if coffee drinking is associated with bladder cancer, the association is a weak one. Other factors that may contribute to the development of bladder cancer include bladder infection with the parasitic fluke Schistosoma haematobium, treatment with the anticancer drugs chlornaphazine or cyclophosphamide, long-term use of pain killers containing the drug phenacetin, urinary tract infections and stasis, dietary factors, tobacco products other than cigarettes (e.g., pipes and cigars), and genetic susceptibility (Silverman et al., in press). |
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