Bladder cancer risks and causes

• A quick guide to what's on this page
• What risk factors are
• How common bladder cancer is
• Smoking
• Chemicals at work
• Treatment for other cancers
• Repeated bladder infections

• Bladder stones
• Diet and fluid intake
• Having had bladder cancer before
• Family history
• Early menopause
• Bladder development before birth

A risk factor is anything that can increase your chance of developing cancer. Different cancers have different risk factors.

Remember that having one or more risk factors does not mean that you will definitely get bladder cancer. Many people who have one or more of the risk factors never get bladder cancer and some people who have none of the risk factors do develop bladder cancer. Risk factors are only a guide to what may increase risk.

About 10,300 people are diagnosed with bladder cancer each year in the UK. It is much more common in men than in women. Not counting non melanoma skin cancer, bladder cancer is the 4th commonest cancer for men, the 10th commonest cancer in women and the 6th commonest cancer overall.

More men than women get bladder cancer. This may just be because more men than women have smoked over the past twenty years or so. And more men have been exposed to chemicals at work.

Your ethnic background is also related to your risk. Black men have about half the risk of bladder cancer of white men. Black women have about two thirds the risk of white women. Risk in Asian men and women is even lower.

Because bladder cancer usually takes a long time to develop, it is most common in older people. Most people with bladder cancer are between 50 and 80 years old. It is rare in people under 40.

Smoking cigarettes definitely increases the risk of bladder cancer. Your risk if you smoke is up to six times that of a non smoker, with the highest risk for people who smoke heavily or have smoked for a long time. In Europe, two thirds of all bladder cancers in men and about a third in women are caused by smoking. Passive smoking also seems to increase the risk. A recent study found that exposure to tobacco smoke during childhood increased the risk of developing bladder cancer.

The chemicals in the smoke get into the bloodstream. They are then filtered out of the blood by the kidneys and end up in the urine. When the urine is stored in the bladder, these chemicals are in prolonged contact with the bladder lining. Chemicals called arylamines in cigarette smoke may be the cause of the increased bladder cancer risk in smokers.

A group of chemicals called arylamines are known to cause bladder cancer. These chemicals have been banned in the UK for about 20 years. But it can take up to 25 years for a bladder cancer to develop. You may have been exposed to them a long time ago if you work in industries such as rubber or plastics manufacture. Arylamines that increase risk of bladder cancer include

• Aniline dyes
• 2-Naphthylamine
• 4-Aminobiphenyl
• Xenylamine
• Benzidine

Another group of chemicals called polycyclic hydrocarbons increase the risk of bladder cancer. Exposure to these chemicals is possible in industries where people handle carbon or crude oil, or substances made from them. You may also come into contact with them in any industry involving combustion, such as smelting.

If you have a diagnosis of bladder cancer, it is worth finding out if you have ever been exposed to any of these chemicals. If you have, talk to your urologist or cancer doctor. You may be able to claim an allowance called 'Industrial Disease Benefit' from the Government Department for Work and Pensions.

Some other jobs and chemicals have been linked to an increased risk of bladder cancer. These include

• Painters and decorator
• Metal casters, machine setters and operators
• Mechanics
• Miners
• People in the printing industry, who work with a substance called 'carbon black' used to make inks

Treatment with radiotherapy to the pelvic area for cancers such as cervical cancer, prostate cancer, kidney cancer, fallopian tube cancer and testicular cancer can increase your risk of bladder cancer. And treatment with the chemotherapy drug cyclophosphamide also increases the risk.

If you have had many bladder infections in the past, or suffer from chronic bladder infection, you may be more at risk from bladder cancer. The risk is particularly high for a type of bladder cancer called squamous cell cancer of the bladder. Smokers who have repeated bladder infections have a much higher risk, with one study reporting a risk 10 times higher than the general population.

In the UK, infection is a much less common cause of bladder cancer than smoking or chemicals. People who are prone to bladder infection are more at risk - for example, people who are paralysed or who have a permanent urinary catheter or regularly self catheterise. A study published in December 2006 also found that men who had gonorrhoea in the past had double the general risk of bladder cancer.

In the developing world, infection is the main cause of bladder cancer. A parasite called bilharzia or schistosomiasis is widespread in many countries and increases the risk of squamous cell bladder cancer.

Bladder stones are little lumps of calcium that can form in the urinary system. You can get kidney or bladder stones. If you have stones in the bladder (sometimes called bladder calculi), you may be more at risk from a type of bladder cancer called squamous cell bladder cancer. This is because stones can cause chronic infection. But you would need to suffer from this for a long time before it would increase your risk of bladder cancer.

A healthy diet may lower your risk of bladder cancer. There is some evidence that eating as little as 100 grams of fruit a day (about 4 ounces) can significantly lower your bladder cancer risk, and the effect might be greater if you eat more than that. But some other studies show that a healthy diet has no effect on bladder cancer risk.

Coffee drinking causes a small increase in bladder cancer risk if you have an extremely high intake (more than 10 cups a day). Researchers have found this in men and women, although the effect is weaker in women. Many other foods have been studied but there is no clear evidence that any of them increase risk of bladder cancer.

Your overall fluid intake probably has no effect on bladder cancer risk. Drinking chlorinated water (water with chlorine added) may cause a small increase in bladder cancer risk compared to water disinfected in other ways.

If you have already been successfully treated for a bladder cancer in the past then your risk of developing another cancer anywhere in the urinary tract is higher. This includes any part of your bladder that is still there after your treatment, your kidneys and the tubes that connect these organs. For this reason your specialist will keep a close eye on you and you will have regular checkups to find any new cancer at its earliest stage. If you have had transitional cell cancer of other parts of the urinary tract (such as the ureters, urethra or renal pelvis) your risk of bladder cancer is also higher than other people in the population.

In a few families, bladder cancer is associated with an inherited faulty gene. But this is very rare. So even if someone in your family has bladder cancer, it is very unlikely that you have an increased risk yourself. If your relative was diagnosed before the age of 45, it is more likely that their cancer was caused by a gene fault. But family cancer patterns are influenced by behaviour too. Often cancers may seem to 'run in families' because of shared patterns of behaviour, such as smoking, which increase the risk of cancer. Overall, you are statistically more at risk if you have a first degree relative with bladder cancer (a parent, child, sister or brother). But remember, this is a statistical risk and can only tell you about risk in a whole population, not a single person.

Two studies show that women who have an early menopause (before the age of 47) have their risk of bladder cancer increased by at least half compared to women who have their menopause at the age of 48 or later. The risk increases by the same amount in women who have both their ovaries removed for medical reasons.

As a baby develops inside the mother there is a connection between their bladder and belly button (umbilicus). This connection is called the urachus and usually disappears before the baby is born. The connection can remain after birth. This is extremely rare but can increase the risk of a rare type of bladder cancer called adenocarcinoma.

Another very rare birth defect called extrophy can also increase a person’s risk of developing bladder cancer later in life. Extrophy occurs when the bladder and urethra do not form properly. The bladder does not form its normal round shape but becomes flat and exposed to the outside of the body. It is turned 'inside out'. With the bladder outside the body and not protected by skin covering, it can easily become infected. This can eventually lead to adenocarcinoma of the bladder.