Bladder Cancer

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Overview, Causes, & Risk Factors

As with most other cancers, the exact cause is uncertain. However, several factors may contribute to the development of bladder cancer.

Cigarette smoking has been shown to increase the risk of developing bladder cancer by a factor of nearly five, compared to non-smokers. As many as 50% of all bladder cancer in men and 30% in women may be attributable to cigarette smoke. This risk, however, does show a gradual decline in individuals who quit smoking.

Studies show that one in four cases of bladder cancer can be attributed to occupational exposure to known carcinogens. Arylamines are a group of chemicals which are responsible for most occupational exposures. Dye workers, rubber workers, aluminum workers, leather workers, truck drivers, and pesticide applicators are at the highest risk; however, the presence of arylamines has been reduced or eliminated in many settings. The association between artificial sweeteners and bladder cancer has been studied and is weak or non-existent.

Women who received radiation therapy for the treatment of cervical cancer have an increased risk of developing transitional cell bladder cancer, as do some people who received the chemotherapy drug, cyclophosphamide (Cytoxan).

Chronic (long term) bladder infection or irritation may lead to the development of squamous cell bladder cancer, however, this cancer is very slow growing. Bladder infections do not predispose to transitional cell cancers.

In third world countries, infection with a parasite (schistosomiasis) has been linked to the development of bladder cancer.

Bladder cancers are classified or staged based on their aggressiveness and the degree that they are different from the surrounding bladder tissue (differentiation). There are several different ways to stage tumors; recently the TNM staging system has become more common. This staging system contains several substages, but it basically categorizes tumors using the following scale:

Bladder cancer is divided into five stages:

• 0 Carcinoma in-situ or non-invasive lesions limited to the bladder mucosa (lining)
• I Tumor extends through the mucosa, but does not extend into the muscle layer
• II Tumor invades into the muscle layer
• III Tumor invades past the muscle layer into tissue surrounding the bladder
• IV Cancer has spread to regional lymph nodes or to distant sites (metastatic)

Bladder cancer spreads by extending into the nearby organs, including the prostate, uterus, vagina, ureters, and rectum. Metastasis can occur to the pelvic lymph nodes or to other parts of the body such as the liver, lungs and bones.