What are Cancer Risk Factors and Why do They Matter?

Talk about risk factors with your healthcare team to make better lifestyle choices.


In 2020, an estimated 1.8 million new cases of cancer were diagnosed in the United States and approximately 600,000 people died from the disease.

A cancer risk factor is anything that increases a person’s chance of getting cancer, yet most risk factors do not directly cause cancer. Simply having a risk factor doesn’t mean a person will develop cancer. Cancer risk is used to describe the chance that a person will get cancer. It is also used to describe the chance that cancer they have or had in the past will recur.

There are risk factors you can control and those that are beyond your control. Through decades of research, scientists have studied common cancer risk factors, a majority of which are related to your lifestyle.


The common risk factors that you CAN control include:

  • Tobacco smoking, chewing or exposure to second-hand tobacco smoke that may increase the risk of lung cancer.

  • Significant alcohol consumption (drinking more than a glass a day for women or more than two glasses a day for men).

  • Lack of exercise and daily physical activity.

  • Obesity.

  • Unhealthy eating habits, including a diet high in processed and unprocessed meat, saturated fat and other ultra-processed junk foods.

  • Excessive sun exposure, or other exposure to ultraviolet light (such as from tanning beds) that may increase the risk of skin cancer.

  • Risky behaviour including unprotected and unsafe sexual activity.

  • Chemical exposure including to asbestos, certain pesticides, fertilizers, herbicides, insecticides and toxins such as vinyl chloride or poly chlorinated biphenyls (PCBs), or from extended years of working in the coal, metal or rubber industries.

  • Infections or viruses such as H. pylori, Epstein-Barr virus, and human papilloma virus.

Here are the risk factors that are NOT under your control:

  • Aging.

  • Previous cancer diagnosis.

  • Family history of cancer.

  • Radiation treatment for certain cancers.

  • Sporadic genetic mutations or inherited cancer cells or mutations such as those for breast and ovarian cancers.

  • Weakened immune system, including from autoimmune diseases such as SLE (lupus), polymyositis/dermatomyositis and inherited immune disorders, such as Sjogren's syndrome.

  • Certain prescribed drugs, such as methotrexate or TNF inhibitors (e.g. Enbrel, Remicade), immunosuppressive drugs used after organ transplants (e.g. azathioprine, cyclosporine), and hormone replacement therapy.



Other risk factors

Factors affecting the workplace and the environment

Cancer can be caused by contamination in the environment or at the workplace. Carcinogens are agents that cause cancer. A few of these carcinogens may cause cancer even if you have not been subjected to them for an extended period of time.

  • Asbestos -Asbestos is a mineral fiber that increases the risk of lung cancer, mesothelioma, laryngeal cancer and ovarian cancer. Asbestos exposure accounts for the highest percentage of occupational cancer risk, especially among workers who also smoke. The federal government regulates asbestos levels in workplaces, but because the fiber is present in the air, water and soil, avoiding asbestos is nearly impossible. Most people who are exposed to the fiber don’t develop disease, but the greater the exposure, the greater the risk. Construction workers, shipbuilders, and boilermakers are amongst those most susceptible to exposure to asbestos at the workplace.

  • Chemicals -Increased risk of bladder cancer has been associated with certain chemical exposures, for example, in workers in rubber manufacturing, transportation, dry cleaning, aluminum production, metalworking and machining, textile and dye manufacturing, painting and hair salons. The higher risk is linked to exposures to aromatic amines, polycyclic aromatic hydrocarbons (PAHs), perchloroethylene, mineral oils/ metal working fluids, diesel exhaust and coal-tar pitch. Arsenic exposure is also linked to increased bladder cancer risk.

  • UV light - Studies suggest that spending too much time in the sun causes numerous skin cancers, including melanoma. People who work mainly outdoors and those with fair skin are the most vulnerable.

Factors that affect your immune system

  • Immune status- Alterations in your immune status from having had a transplant or from taking immunosuppressive drugs to prevent the body from rejecting the transplant can also increase risk of cancer.

  • HIV- Compared with the general population, people infected with HIV are currently about 500 times more likely to be diagnosed with Kaposi sarcoma, 12 times more likely to be diagnosed with non-Hodgkin lymphoma, and, among women, 3 times more likely to be diagnosed with cervical cancer

Bacteria and Viruses

Virus infections are relatively common, yet the majority of these infections almost never result in malignancy. A small proportion of viruses have been related to an increased risk of developing cancer. The most common viruses include:

  • Human papillomavirus -HPV has been associated with a variety of malignancies including cervical cancer.

  • Epstein-Barr virus-This virus has been associated with certain kinds of lymphoma.

  • Hepatitis B and C -These viruses have been linked to the development of liver cancer.

  • HIV –This can raise your risk of cancers like Kaposi’s sarcoma and lymphoma.

  • HTLV-1 virus: This virus has been linked to adult T cell leukemia/lymphoma.

  • Infection with Helicobacter pylori ( a type of bacteria) causes chronic inflammation and significantly increases the risk of developing gastric cancer. Infection with H. pylori is the strongest known risk factor for gastric cancer, which is the second leading cause of cancer-related deaths worldwide.

It helps to be aware of your risk factors. Talking to your doctor is the first step in getting a deeper understanding of how your risk factors can affect you.

Here are some questions to get the conversation started:

  • What are my chances of getting cancer within the next five years and during the course of my life?

  • What are the ways to lower my risk of developing cancer?

  • If I change my behaviour to eliminate a risk factor (for example, quit smoking), how does it change my risk of developing cancer in the next five years and over my lifetime?

  • What happens if I learn about a new risk factor, such as relative acquiring cancer?

  • What cancer screening tests do you recommend? How often should I have them?


The cause of most cancers is multifactorial meaning that a combination of certain factors including but not limited to genetic, environmental, lifestyle, medical, etc. increases cancer risk. If you have a genetic predisposition to cancer it does not mean that you will develop the disease. Likewise, if you do not have a genetic predisposition you may still be at risk. Knowing your cancer risk will help your doctor determine whether you might benefit from screening tests at a regular schedule or more frequently and whether certain prophylactic steps including surgery or drugs may reduce your risk of developing cancer. Genetic counseling is important for people who may have a genetic predisposition to cancer to understand accurately the limitations of cancer screening and genetic testing as well as to be prepared to deal with the results of these tests.


Reason to hope: The U.S. Preventive Services Task Force recommends that adults with average risk start colon cancer screening at age 45 instead of waiting until 50. Additionally, new data suggests that certain adults between the ages of 76 and 85 years might also benefit, although to a lesser extent.


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