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What are bladder cancer causes and risk factors?
About 50% of all bladder cancers may be caused by cigarette smoking. The longer and heavier the exposure, greater are the chances of developing bladder cancer. The toxic chemicals in cigarette smoke, many of which are known cancer-causing substances (carcinogens), travel in the bloodstream after being absorbed from the lungs and get filtered into the urine by the kidneys. They then come in contact with the cells in the inner lining of the urinary system, including the bladder, and cause changes within these cells that make them more prone to developing into cancer cells. Quitting smoking decreases the risk of developing bladder cancer but takes many years to reach the level of people who have never smoked. However, as time passes after the quit date, the risk progressively decreases. In view of the above, it is extremely important for patients with bladder cancer to stop smoking completely since the chances of the cancer coming back after treatment are higher in those people who continue to smoke.
People who smoke also have a higher risk of many other types of cancer, including leukemia and cancers of the lung, lip, mouth, larynx, esophagus, stomach, and pancreas. Smokers also have a higher risk of diseases like heart attacks, peripheral vascular disease, diabetes, stroke, bone loss (osteoporosis), emphysema, and bronchitis.
Age and family history are other risk factors as is male sex. About 90% of people with bladder cancer are over age 55, though in exceptional cases the disease may surface in the third or fourth decade of life. Men are more prone to developing bladder cancer probably due to a higher incidence of smoking and exposure to toxic chemicals. A close relative with a history of bladder cancer may increase the predisposition for the development of this disease.
Exposure to toxic chemicals such as arsenic, phenols, aniline dyes, and arylamines increase the risk of bladder cancer. Dye workers, rubber workers, aluminum workers, leather workers, truck drivers, and pesticide applicators are at the highest risk. Recently, the drug pioglitazone (Actos), used to treat type 2 diabetes, has been suspected to increase a person’s risk to develop bladder cancer.
Radiation therapy (such as that for prostate or cervical cancer) and chemotherapy with cyclophosphamide (Cytoxan) has been shown to increase the risk for development of bladder cancer. Moreover, it may also delay the diagnosis of bladder cancer in patients presenting with symptoms of bleeding in urine since this bleeding may be incorrectly attributed by the patient and/or the physician to the bladder irritation caused by the chemotherapy or radiation (radiation cystitis).
Long-term chronic infections of the bladder, irritation due to stones or foreign bodies, and infections with the blood fluke prevalent in certain regions of the world (as mentioned earlier) are some other factors which predispose to bladder cancer.