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Causes of mouth cancer

By Dr Ananya Mandal, MD

Cancer cells are normal cells whose DNA and genes are altered to cause them to multiply and grow abnormally.

The DNA within the cell provides it with basic set of instructions, such as when to grow and reproduce. When this changes on account of a mutation, the instructions go haywire. The uncontrolled growth of the cells lead to formation of a lump of tissue called a tumour. 1-6

What parts of the body does mouth cancer affect?

Oral cancer or mouth cancer affects the insides of the mouth, tongue, gums and lips.

The cancer from the mouth may spread to nearby tissues, such as surrounding skin or into the back of the jaw or may spread via the lymphatic system or blood vessels to far off organs such as liver, lungs and brain.

This is an advanced stage of the cancer and is usually difficult to treat. Mouth cancer that spreads to another part of the body is known as metastatic oral cancer.

Risk factors for mouth cancer

The underlying causes that trigger the changes in DNA leading to the cancer in the mouth are not well known. However, there are certain risk factors that raise the chances of getting mouth cancer. These include smoking and alcohol consumption, chewing tobacco and so forth.

Smoking, alcohol consumption and mouth cancer risk

These are the most common causes of oral cancer. Smoking cigarettes and other tobacco products, such as pipes or cigars as well as taking in too much alcohol causes the mouth to be exposed to carcinogens or chemicals that can damage the DNA and make the cells cancerous.

The risk of mouth cancer increases significantly in people who are both a heavy smokers and heavy drinkers.

There are studies that have shown that heavy smokers who smoke 40 cigarettes a day, but do not drink, are five times more likely to develop mouth cancer than someone who does not drink or smoke.

On the other hand a person who does not smoke but drink an average of 30 pints a week raises the risk of mouth cancer by five times as well.

When these two habits are combined in an individual (more than 40 cigarettes a day as well as average of 30 pints of alcohol a week) the risk of developing mouth cancer becomes 38 times higher!

Chewing tobacco and mouth cancer risk

Those who use chewing tobacco are also at a much higher risk than those who smoke cigarettes on account of direct exposure of the inner linings of the mouth to the carcinogens.

Other types of smokeless tobacco use includes the use of snuff (powdered tobacco designed to be snorted or inhaled) and snus that is a type of smokeless tobacco popular in Sweden, which is placed under the upper lip, where it is gradually absorbed into the blood stream.

Chewing betel nuts and mouth cancer risk

Betel nuts are mildly addictive seeds taken from the betel palm tree. These are chewed by Southeast Asian ethnic communities from India and Sri Lanka. These contain a stimulant similar to caffeine. These nuts contain carcinogens that raise the risk of mouth cancers.

Those who chew both betel nuts and tobacco together are naturally at a higher risk. It is because of this habit that rates of mouth cancer are much higher in ethnic Indian and Sri Lankan communities than in the population at large.

Chewing qat and mouth cancer risk

Qat is a green-leafed plant found in Africa and southern Arabia with a mild stimulant effect. It may be chewed with tobacco. Both together raise the risk of mouth cancers.

Cannabis smoking and mouth cancer risk

Cannabis smoking is another risk factor for mouth cancer. Regular cannabis smokers may have a higher risk than tobacco smokers because these contain higher levels of tar than tobacco smoke. This is carcinogenic or cancer causing.

Exposure to viruses and mouth cancer risk

Exposure to viruses like Human papilloma virus (HPV). HPV can affect the mucous linings of the cervix, anus, mouth and throat. This is a sexually transmitted virus that is implicated in genital warts and cancers of the cervix and vulva.

Some types of HPV infection may lead to cancers in the mouth as well. This is commonly seen in the younger population.

Poor diet and mouth cancer risk

Poor diet is another risk of mouth cancer. Those who consume too much red meat, processed food and fried food and too little fruits and vegetables in their diet are at a higher risk of mouth cancer.

Poor oral hygiene and mouth cancer risk

Poor oral hygiene, like having a decayed tooth, not brushing or flossing regularly, gum disease and having ill-fitted dentures raise the risk of mouth cancer.

Excessive sun light exposure and mouth cancer risk

Excessive sunlight exposure is related to the cancer of the lip.

Age and sex and mouth cancer risk

Mouth cancers are more common in older people and there is a high incidence even among those in their 40’s and 50’s.

Previously, men were more at risk owing to their heavier smoking and drinking habits. However, rates of mouth cancer in women is slowly catching up with men. Mouth cancers are still more common in men.

History of other head and neck cancers and mouth cancer risk

Those with an earlier history of other head and neck cancers are at a raised risk of mouth cancers especially if they are smokers and drinkers.

Medications and mouth cancer risk

Certain medications that supress the immunity, such as those used in post- kidney transplant patients, also raise the risk of mouth cancers.

The risk is also increased in conditions which suppress the immune system like HIV/AIDS infection.

Paterson Brown-Kelly syndrome

Paterson Brown-Kelly syndrome (Plummer-Vinson syndrome) is a condition that is thought to raise the risk of cancer of the oral cavity.

Reviewed by , BA Hons (Cantab)

Further Reading

Last Updated: Aug 13, 2012

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