Causes of cancer

Scientists still do not know what causes all types of cancer and usually the reason for why some people develop cancer and others don´t are down to many different factors. Below you can read about the most important causes we know of so far.

Age

It may seem strange to say that age is a cause of cancer but we do know that the risk of cancer increases as we get older. This is because it usually takes a long time for changes to happen in the cells that cause cancer to develop. When we’re older our body has been exposed to cancer causing factors in our environment for a long time so that what used to be normal cells can become so faulty that they become cancerous. Also, as we get older our body cells get more worn and therefore faults in the cells can occur more easily.

Genes and cancer

It may be easier to understand about genes and cancer if you first read the section called ‘Genetics of cancer’. Basically, genes are part of our DNA that exist inside all our body cells and they instruct our cells on how to behave. Therefore, if a gene becomes faulty (we call this a mutation) the instruction to the cell can be lost or changed so that the cell can start behaving in an abnormal way. The damaged gene for example, can change its instruction/code so that the cell is told to keep dividing and produce more cells when in fact it shouldn’t. A damaged cell that can’t be repaired should normally die and not create more cells. Because when a damaged cell produce more cells, the new cells will also have the same fault and so more and more faulty cells will be created and bundle together and then they can develop into cancer.

Usually when faults occur in our cells they happen during our lifetime and the majority are not faults that we were born with. And therefore faults in our genes that develop into cancer are in most cases NOT inherited from our parents. It’s easy to think that cancer is inherited if many people in the same family get cancer. But we must remember that cancer is such a common disease that it is normal for several people within the same family to develop cancer without there being any gene faults that have been inherited. Usually when many people within the same family get cancer it is just a coincidence or because family members often are exposed to the same factors that can cause gene faults to develop.

So it is rare, but it is possible though, to inherit a gene fault from our parents that can increase our risk of developing cancer. Researchers are working to find genes that increase people’s risk of developing cancer. The first faulty genes that scientists found that could be inherited were two genes which were named BRCA1 and BRCA2. These two genes have been found to increase people’s risk of developing breast cancer and ovarian cancer because they can be passed on in generations. Still, only 3 out of 100 people (3%) with breast cancer have got such an inherited gene so most cases of breast cancer is therefore not inherited. Researchers have also found other faulty genes that can be inherited and increase our risk of getting cancer and more such genes are likely to be found in the future. However, most cancers develop because of gene faults that occur due to chance and our environment and a combination of these factors.

Smoking, drinking, diet and other daily habits

So therefore, it is much more common that rather than inheriting mutated genes, they get damaged by something we do, like inhaling cigarette smoke. Cigarette smoke contains carcinogens. Carcinogens are substances that can cause genes to develop faults. Most people know that smoking tobacco increases the risk of developing lung cancer. However, there are many other types of cancer where smoking also increases the risk, such as cancers in the head and neck areas like the throat, voice box, mouth, lips, nose, sinuses and swallowing tube, and also cancers of the bladder, kidneys, stomach, pancreas, uterus, cervix, bowels, ovaries and a type of leukemia called myeloid leukemia. So you can see from this long list that cigarette smoking really is a very important factor which increases the risk of developing many types of cancer. Therefore, stopping smoking / or even better don’t start smoking is a very good way of reducing your risk of getting cancer.

Drinking too much alcohol also raises the risk of developing certain types of cancer such as cancer of the mouth, throat, voice box, food pipe, breast, colon, rectal and liver. For some of these cancers, the risk is increased even more in people who both smoke and drink too much alcohol. The good thing is that these are both factors you can control yourself!

We hear a lot in the media about how various foods and diets may be linked to either developing cancer or protecting against cancer. Although there are lots of research in this area, it is very complicated to study because there are so many factors involved. Also, because cancer can take such a long time to develop it is hard to find out how a cancer may be specifically linked to people’s diet. What we do know so far is that eating a lot of fruit and vegetables (at least 5 portions per day) helps protect against cancer but eating a lot of red meat (beef, lamb and pork), too much salt and not enough fibre increase the risk of developing cancer.

There is also a lot of talk about the increase of obesity (when people are more than 25% overweight) in our society and the risks of being overweight. This is also linked to cancer as people who are overweight or obese have a higher risk of developing cancer in the bowel, pancreas, food pipe, kidney, gallbladder, breast and womb. The reasons why obesity increases the risk of cancer are complicated but seem to have an impact on the immune system, hormone levels and factors that affect how cells divide and are renewed in our bodies. One way to control your weight is to eat healthily and being physically active is another way of reducing the risk of becoming overweight. This will have a positive impact on reducing cancer risks and is also good for reducing your risk of heart disease and diabetes too.

Radiation

Another factor that you probably have heard of which can cause cancer is UV radiation. Radiation is a type of energy that is sent out from any type of source and UV radiation is a form of electromagnetic radiation. The main source of this type of radiation is the sun sending out sun rays. It’s important to know though, that sun beds also give out UV radiation and can be just as damaging as radiation from the sun, particularly when people start using them before the age of 30 years. Other types of radiation can also increase people’s risk of developing cancer and this can be radiation from the earth and space and radiation in work places.

Other carcinogens

Carcinogens are any substances or agents (including radiation) that have a role in causing cancer to develop. Tobacco smoke is a carcinogen that most people are aware of but there are other carcinogens that also increase people’s risk of developing cancer. Sometimes it can take a long time and a lot of research to find out if something is carcinogenic and if something contains too high levels of a carcinogenic substance, it is decided that such substances cannot be used anymore. Still, there can also be carcinogenic substances in things that are deemed safe for us because the levels of carcinogenic substance are so small that we couldn’t possible manage to get enough of the substance in our bodies in order for it to cause cancer to develop.

Viruses and bacterial infections

There are some viruses that can increase people’s risk of developing certain types for cancer. This does not mean that cancer can be caught through viruses that cause infections but some viruses can cause gene faults to develop inside body cells and then those faults can lead to cancer cells developing. For example, a virus called the human papilloma virus (HPV) can lead to cervical cancer and hepatitis B and C viruses can lead to liver cancer. There is also research that investigates if bacterial infections are linked to cancer and so far we know that people who have a certain bacteria (helicobacter pylori) in their stomach have an increased risk of developing stomach cancer.

If you want to know more about this topic you can have a look at CancerLinks’s section on preventing cancer. Also, you can get in touch with us here at riprap anytime if you have any queries or just want to talk things through.

Page updated 6 July 2017