Incidence and Mortality
Bladder cancer is the fourth most commonly diagnosed malignancy in men in the United States. It is estimated that 69,250 new cases of bladder cancer are expected to occur in the United States in 2011.
Bladder cancer is diagnosed almost twice as often in whites as in blacks of either sex. The incidence of bladder cancer among other ethnic and racial groups in the United States falls between that of blacks and whites. The incidence of bladder cancer increases with age.
Since the 1950s, the incidence of bladder cancer has risen by approximately 50%. It is to be anticipated that, with the aging of the U.S. population, this trend will continue. There has been a decrease of approximately 33% in bladder cancer mortality during the same interval (National Cancer Institute's Surveillance, Epidemiology, and End Results program, 1973-1997). It is estimated that 14,990 Americans will die of bladder cancer in 2011.
The age-adjusted mortality from bladder cancer has decreased in all races and sexes during the past 30 years, but blacks and women have a disproportionately higher mortality rate than that of white males. These changes may reflect earlier diagnosis, better therapy, less exposure to carcinogens, or some combination of these factors.
More than 90% of cancers in the bladder are transitional cell carcinomas (TCC), also called urothelial cancer. Other important histologic types include squamous cell carcinoma and adenocarcinoma. Urothelial cancer can also rarely develop in the lining of the renal pelvis, ureter, prostate, and urethra.
There are no definitive studies on the prevention of bladder or other urothelial cancers. Reduction in environmental and occupational exposures would presumably reduce urothelial cancer risk. Differences in age, gender, race, and geographic distribution may reflect differences in environmental and occupational exposure to possible toxicants. Relevant exposures include chemical exposures; cigarette smoking; infection with bacteria, parasitic fungi, or viruses; harboring bladder calculi; and treatment with certain chemotherapeutic agents.
Several populations with a variety of exposures appear to be at higher risk of developing bladder cancer. By far, the greatest known environmental risk factor in the general population is tobacco, especially cigarette smoking; individuals who smoke have a fourfold to sevenfold increased risk of developing bladder cancer than individuals who have never smoked.[4,5,6] Risk is reduced with cessation of smoking, but a relatively small decrease in incidence is seen for the first 5 to 7 years after cessation. Even after 10 years, the risk of an individual developing bladder cancer is still almost twice that of an individual who has never smoked.
Among the chemicals implicated in smoking-induced bladder cancer are aminobiphenyl and its metabolites. It is possible that inherited and inducible enzymes are important in the activation and detoxification of aminobiphenyls and other putative bladder carcinogens. These enzymes include N-acetyltransferase 2 (NAT2), cytochrome P450 1A2 (CYT 1A2), and glutathione S-transferase M 1. Several studies have indicated that specific genotypes and phenotypes of these enzymes and their activities, particularly in the liver and urothelium, are associated with susceptibility to smoking-induced bladder cancer and bladder cancer induced by other aryl amines, particularly in industrially exposed populations.[8,9,10,11,12,13] Not all of these studies, however, have been well controlled for active or former smoking histories.