No one knows exactly what causes cancer and why some people get it and others don’t – often people from the same family, or people exposed to the same environmental conditions or suffering from the same health problems don’t follow the same patterns when it comes to getting cancer.
Cancer is unpredictable –it can happen that a non-smoker develops cancer and a heavy smoker does not. But risk factors describe probabilities - a risk factor can merely describe the chance that someone will develop cancer.
Over the past few decades cancer researchers have noticed a pattern in the development of cancer in some specific groups, and based on that have formulated a number of risk factors to help doctors with early detection of cancer in their patients. This increases the chances of effective treatment.
But what are those risk factors? The National Institutes of Health and the Merck Manuals suggest the following:
Heredity. Generic inheritance plays a role in the likelihood that someone will develop cancer as they may have inherited certain genetic mutations from your parents. But inherited genetic changes are actually quite rare. It is possible to have genetic testing done in order to test your likelihood of developing certain cancers.
Age. Although some cancers affect mostly children, the vast majority of cancers affect people who are older than 65. And 25% of new cancer cases are diagnosed in people over the age of 74. It is thought that older people have simply been exposed to cancer-causing agents (carcinogens) for a longer period of time, and also that their immune system, which is involved in detecting and eliminating cancer cells, may not function as efficiently as it does in younger people.
Exposure to environmental carcinogens. These include exposure to ultraviolet rays from the sun, pollutants in the air or water, such as asbestos or industrial pollutants or pesticides, exposure to radiation, or the radioactive gas, radon, tobacco smoke (even second hand smoke). There is a long list of environmental toxins which are thought to be culprits in the causing of cancer, and generally the rule is the greater a person’s exposure to the toxin, the greater the risk. These range from aflatoxins, benzene, coal tar, formaldehyde, nickel compounds, soot and wood dust, to name but a few.
Geography. This is thought to be a combination of genetics, diet and environment – urban populations generally have higher cancer rates than rural populations, especially in agricultural communities where exposure to carcinogens is low. In some countries, such as Japan, the cancer rates (except stomach cancer) are lower than in other countries.
Chronic inflammation. An overreaction of the immune system may be to blame for this response in some cases. But sometimes people just have an inflammation that does not go away and this can ultimately lead to DNA damage and to cancer.
Food and drink. A diet high in unsaturated fat is thought to contribute to your cancer risk. Smoked, pickled or barbecued foods are also suspects as are certain preservatives. Alcohol usage - more than one drink a day for women and more than two drinks a day for men (and more than one a day for all people over the age of 65) is also a risk factor.
Sun exposure. Regular exposure to the sun between 10 am and 4pm, and getting sunburnt regularly, are both high risk factors for skin cancer. Sunlamps and tanning booths also all give off ultraviolet radiation, which increases the risk for skin damage that can lead to skin cancer.
Obesity and overweight. Extra weight increases the risk for certain cancers, such as cancers of the breast, the colon, the rectum, the oesophagus, the kidneys, the pancreas and the gallbladder.
Smoking and exposure to second hand smoke. Tobacco products and even secondhand smoke contain lots of chemicals that can damage your DNA. Smoking is a leading cause of cancer and of death from cancer. Tobacco use does not just increase the risk for lung cancer – it also increases the risk for cancers of the larynx, the mouth, the oesophagus, throat, bladder, kidney, liver, stomach, pancreas, colon, rectum and cervix.
Hormones. Oestrogen, especially, is known as a carcinogen, and plays a role in increasing the risk factor for cancers of the breast and endometrial cancer. Risks and benefits of taking hormone replacement therapy therefore need to be considered carefully.