It is often unclear why one person develops cancer and another does not. Two people leading seemingly similar lifestyles could have very different responses relating to cancer. Research however shows that the possibility of a person developing cancer is a result of the interaction between the person’s genetic makeup and exposure to certain external agents or carcinogens. A carcinogen is a substance capable of causing cancer in humans or animals.

Therefore, the factors that could increase the chances of a person developing cancer fall into two groups, external avoidable factors and internal unavoidable ones. Avoidable factors, as the name suggests, can be controlled to reduce a person’s chances of developing cancer. Unavoidable factors unfortunately cannot be controlled. Sometimes a combination of these factors could also lead to the development of cancer.

While reading about these factors and thinking about your own chances of getting cancer, please remember that having one or more risk factors does not mean you will get cancer! Most people who are exposed to these risk factors may never develop cancer.


Avoidable factors are those that people can control in order to reduce their risk of getting cancer. Having a clear understanding of these factors and taking appropriate action is therefore advised for each individual. Some common avoidable factors are:

  • Tobacco consumption
    Tobacco use is the most preventable cause of cancer. Using tobacco products or being around tobacco smoke (environmental or second-hand) increases the risk of cancer. While smokers are more likely to develop cancer of the lung, voice box, mouth, oesophagus, bladder, kidney, throat, stomach, pancreas, or cervix, people who chew tobacco or take snuff are at an increased risk of cancer of the mouth.

  • Environment exposure
    Radiation is a carcinogen which is found in different sources. In our natural environment, ultraviolet radiation from the sun can cause early aging and skin damage which could lead to cancer. Medical procedures that require exposure to high dose of x-rays or radiation should be avoided unless necessary. Studies have also shown that exposure to chemicals like asbestos, benzene, benzidine, cadmium, nickel or vinyl chloride may also cause cancer. Also, research has found that miners working in deep underground mines may have increased radon exposure which could lead to lung cancer.

  • Alcohol consumption
    The risk of cancer increases with the amount of alcohol a person consumes. Having more than the recommended amount each day (2 units* for women, 3 units for men) for many years may increase the chance of developing cancers of the mouth, throat, oesophagus, larynx, liver, and breast. The risk increases further for a drinker who also uses tobacco.

    *(1 unit = 10ml/8g of pure alcohol, a single glass of spirits (35ml) = 1.5 units, a standard glass of wine = 2 units, a pint of regular beer = 2 units)
  • Diet, Exercise and Weight Control People who have poor diet, who do not have enough physical activity, or who are overweight may be at increased risk of several types of cancer. Studies indicate that people whose diet is high in fat have an increased risk of cancers of the colon, uterus, and prostate. Lack of physical activity and being overweight are risk factors for cancers of the breast, colon, oesophagus, kidney, and uterus. Healthy food choices and a well-balanced diet including fibre, vitamins, minerals and low fat items may help reduce cancer risk.


Unavoidable factors are those that cannot be controlled by an individual. For cancers caused by unavoidable factors, it is important to detect the cancer as early as possible in order to increase a person’s chances of beating and surviving the disease. It is therefore important for all individuals to undergo timely and age-appropriate cancer screening.

  • Age
    Ageing is a fundamental factor for the development of cancer. The incidence of cancer rises dramatically with age, most likely due to a build-up of risks for specific cancers that increase with age. The accumulation of these risks when combined with the tendency of less effective cellular repair mechanisms (due to old age) makes age a key risk factor.

  • Family history
    Most cancers develop because of changes to the genetic material of the body. Some of these changes can be passed from parent to child and are present at birth in all cells of the body. It is uncommon for cancer to run in a family but certain types of cancer do occur more often in some families than in the rest of the population. For example, melanoma and cancers of the breast, ovary, prostate, and colon sometimes run in families. While several cases of the same cancer type in a family may be linked to inherited gene changes, most of the time, multiple cases of cancer in a family are just a matter of chance.

  • Viruses and bacteria Being infected with certain viruses or bacteria may increase the risk of developing cancer. For example Human Papillomaviruses (HPVs) are the main cause of cervical cancer. They may also be a risk factor for other types of cancer. Hepatitis B and Hepatitis C viruses could lead to the development of liver cancer after many years of infection. People who have Human Immunodeficiency Virus (HIV) infection are at greater risk of cancer, such as lymphoma and a rare cancer called Kaposi sarcoma. The Helicobacter pylori virus causes stomach ulcers which can also cause stomach cancer and lymphoma in the stomach lining.

  • Hormones Hormones could play a key role in the development of cancer. For example breast cancer is highly dependent on hormones for growth. The female hormones oestrogen and progesterone commonly influence breast cancer growth. Blocking the effects of these hormones using drugs on breast tissue inhibits cancer growth and is used clinically. These hormones are also used in the management of advanced gynaecological cancers. In the case of thyroid cancer, suppression of the thyroid hormone is used to supress cancer. It is therefore advisable that any form of hormone therapy be taken under strict doctor supervision.

If you are concerned about how some factors might affect you, contact us or speak to your doctor.