Cancer begins with a change in the structure of deoxyribonucleic acid (DNA). DNA provides our cells with a basic set of instructions, such as when they should grow and reproduce.
A change in the structure of DNA is known as a mutation and it can change the instructions that control cell growth. This means that the cells will continue to grow and reproduce uncontrollably, producing a lump of tissue called a tumour.
How does bladder cancer spread?
Left untreated, bladder cancer will spread from the lining of the bladder into the surrounding muscles. Once the cancer has reached the muscles, it is able to spread to other parts of the body, usually through the lymphatic system.
The lymphatic system is a series of glands (or nodes) that are located throughout your body. It is similar to the blood circulatory system. Lymph glands produce many specialised cells that are needed by your immune system to fight infection.
Once the cancer reaches the lymphatic system, it can spread to any other part of your body, including your bones, blood and organs. The spread of cancer to other parts of the body is known as metastasis.
Risk factors
What causes a person’s DNA to change and bladder cancer to develop is not always known.
However, several risk factor have been identified, which are discussed below.
Smoking
Smoking is the single biggest risk factor for bladder cancer. This because tobacco contains more than 40 different types of carcinogenic (cancer-causing) chemicals.
If you smoke for many years, the carcinogenic chemicals will pass into your urine and begin to coat the lining of your bladder. This can then cause genetic mutations that lead to the development of bladder cancer.
It is estimated that half of all cases of bladder cancer are related to smoking, and people who smoke may be as much as six times more likely to develop bladder cancer than non-smokers.
Exposure to chemicals
Exposure to certain chemicals is the second biggest risk factor for bladder cancer. Previous studies have estimated that this may account for around 25% of cases.
Chemicals known to increase the risk of bladder cancer include:
- aniline dyes
- 2-Naphthylamine
- 4-Aminobiphenyl
- xenylamine
- benzidine
Occupations that have been linked to an increased risk of bladder cancer are manufacturing jobs that involve the following:
- rubber
- dyes
- textiles
- plastic
- chemicals
The link between bladder cancer and these types of occupations was discovered in the 1970s and 1980s. Since then, regulations relating to exposure to cancer-causing chemicals have been made much more rigorous and many of the above chemicals have been banned.
At the moment, the proportion of occupation-related cases of bladder cancer that are diagnosed is still quite high. This is because it can take up to 25 years after initial exposure to the chemicals before bladder cancer starts to develop.
However, due to the introduction of much tighter regulations regarding the use of chemicals, the number of occupation-related cases of bladder cancer should start to decrease in the future.
Other risk factors
Other risk factors for bladder cancer include:
- having radiotherapy to treat previous cancers that occurred near the bladder, such as a kidney cancer
- having a permanent tube in your bladder (an in-dwelling catheter) to drain away urine because you have nerve damage that has resulted in paralysis; this is often the case in people who have had a spinal cord injury
- having previous treatment with a chemotherapy medication called cyclophosphamide which is often used to treat breast cancer and ovarian cancer
- taking a type of steroid medication called glucorticoids on a long-term basis; this type of medication is often used to treat allergic conditions or conditions where the immune system attacks healthy tissue (autoimmune conditions), as well as being used to prevent the body rejecting donated organs
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Causes of bladder cancer
