What are the risk factors for bladder cancer?


A risk factor is anything that changes your chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, like smoking, can be changed. Others, like a person’s age or family history, can’t be changed.

But risk factors don’t tell us everything. Having a risk factor, or even several, does not mean that you will get the disease. Many people with risk factors never develop bladder cancer, while others with this disease may have few or no known risk factors.

Still, it is important to know about some of the risk factors for bladder cancer because there may be things you can do that might lower your risk of getting it. If you are at higher risk because of certain factors, you may benefit from tests that might help find it early, when treatment is most likely to be effective.

There are several risk factors that make a person more likely to develop bladder cancer.

Smoking

Smoking is the most important risk factor for bladder cancer. Smokers are at least 3 times as likely to get bladder cancer as nonsmokers. Smoking causes about half of the bladder cancers in both men and women.

When smokers inhale, some of the carcinogens (cancer-causing chemicals) in tobacco smoke are absorbed from the lungs and get into the blood. From the blood, they are filtered by the kidneys and concentrated in the urine. These chemicals in urine can damage the cells that line the inside of the bladder, which increases the chance of cancer developing.

Workplace exposures

Certain industrial chemicals have been linked with bladder cancer. Chemicals called aromatic amines, such as benzidine and beta-naphthylamine, which are sometimes used in the dye industry, can cause bladder cancer.

Other industries that use certain organic chemicals also may put workers at risk for bladder cancer if exposure is not limited by good workplace safety practices. The industries carrying highest risks include the makers of rubber, leather, textiles, and paint products as well as printing companies. Other workers with an increased risk of developing bladder cancer include painters, machinists, printers, hairdressers (likely because of heavy exposure to hair dyes), and truck drivers (likely because of exposure to diesel fumes).

Cigarette smoking and workplace exposures may act together to cause bladder cancer. Smokers who work with the cancer-causing chemicals noted above have an especially high risk of developing bladder cancer.

Race and ethnicity

Whites are about twice as likely to develop bladder cancer as African Americans. Hispanics, Asian Americans, and American Indians have slightly lower rates of bladder cancer. The reasons for these differences are not well understood.

Age

The risk of bladder cancer increases with age. About 9 out of 10 people with bladder cancer are over the age of 55.

Gender

Bladder cancer is much more common in men than in women.

Chronic bladder irritation and infections

Urinary infections, kidney and bladder stones, and other causes of chronic bladder irritation have been linked with bladder cancer (especially squamous cell carcinoma of the bladder), but it is not clear if they actually cause bladder cancer.

Schistosomiasis (also known as bilharziasis), an infection with a parasitic worm called Schistosoma hematobium that can get into the bladder, is also a risk factor for bladder cancer. In countries where this parasite is common (mainly in Africa and the Middle East), squamous cell cancers of the bladder are seen much more often. This parasite is an extremely rare cause of bladder cancer in the United States.

Personal history of bladder or other urothelial cancer

Urothelial carcinomas can form in many areas in the bladder as well as in the lining of the kidney, the ureters, and urethra. Having a cancer in any part of the urinary tract lining puts you at higher risk of having another tumor. The tumor can form in the same area as before, or in another part of the urothelium (lining). This is true even when the first tumor is completely removed. For this reason, people who have had bladder cancer need close, routine medical follow-up.

Bladder birth defects

Before birth, there is a connection between the belly button and the bladder. This connection, called the urachus, normally goes away before birth. If part of this connection remains after birth, it could become cancerous. Cancers that start in the urachus are usually adenocarcinomas, which are made up of malignant gland cells. About one third of the adenocarcinomas of the bladder start here. However, this is still rare, accounting for less than a half of 1% of all bladder cancers.

Another rare birth defect called exstrophy greatly increases a person’s risk of developing bladder cancer. In bladder exstrophy, both the bladder and the abdominal wall in front of the bladder fail to close completely during development and are fused together. This leaves the inner lining of the bladder exposed outside the body. Surgery soon after birth can close the bladder and abdominal wall (and repair other related defects), but patients who have this are still at increased risk for urinary infections and bladder cancer.

Genetics and family history

People who have family members with bladder cancer have an increased risk of getting it themselves. In some cases, these family members may all be exposed to the same cancer- causing chemical. They may also share changes in some genes (like GST and NAT) that cause their bodies to be slow to break down certain toxins, which may make them more likely to develop bladder cancer.

A small number of people inherit a gene syndrome that increases their risk for bladder cancer. For example:

  • A mutation of the retinoblastoma (RB1) gene can cause cancer of the eye in infants, and also increases the risk of bladder cancer.
  • Cowden disease, caused by mutations in a gene called PTEN, is linked mainly to cancers of the breast and thyroid. People with this disease also have a higher risk of bladder cancer.
  • Lynch syndrome (also known as hereditary non-polyposis colorectal cancer, or HNPCC) is mainly linked to colon and endometrial cancer. People with this syndrome also have an increased risk of bladder cancer, as well as cancer of the ureters.

Chemotherapy and radiation therapy

Long-term use of the chemotherapy drug cyclophosphamide (Cytoxan) can irritate the bladder and increase the risk of bladder cancer. People taking this drug are often told to drink plenty of fluids to help protect the bladder from irritation and decrease the risk of bladder cancer.

People who are treated with radiation to the pelvis are more likely to develop bladder cancer.

Arsenic

Arsenic in drinking water has been linked with an increased risk of bladder cancer. The chance of being exposed to arsenic depends on where you live and whether you get your water from a well or from a system that meets the standards for arsenic content.

Low fluid consumption

Not drinking enough fluids may increase the risk of bladder cancer. People who drink a lot of fluids each day have a lower rate of bladder cancer. This is thought to be because they empty their bladders often. By doing this, they keep chemicals from lingering in their bodies.

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