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The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on May 14, 2021.

Cancer risk factors

A number of factors may increase the risk for developing cancer, whether it’s weight, diet, tobacco use or family history. However, simply having a risk factor doesn’t mean a person will develop cancer. Instead, these risk factors have been identified through research as having some relationship to different types of cancer.

Some lifestyle changes may help reduce the risk of developing cancer, but other risk factors are unavoidable, such as age, race or family history. A doctor may advise you on recommended screenings and potentially concerning symptoms to be aware of.

What are the causes of cancer?

Our bodies consist of trillions of cells that are constantly being replicated over the course of a lifetime. There are hiccups in the DNA replication process, when new cells don’t form as intended, creating mutations. When these abnormal cells appear, the body’s immune system is designed to find and remove them. Cancer is the uncontrolled growth of abnormal cells in the body. It develops when the body’s normal control mechanisms stop working. These mutated cells may form a mass of tissue, called a tumor, although some cancers, such as leukemia, don’t have tumors.

While scientists know that these changes in cells may cause cancer to develop, they are still trying to understand all the steps of the process. Likewise, for most risk factors, scientists have established a connection even if they don’t know the specific interplay that produces the cancer.

Risk factors you can control

Through decades of cancer research, scientists have determined a range of common cancer risk factors. Many are lifestyle choices that may be changed to reduce the risk. Some of the most common controllable cancer risk factors include:

  • Tobacco smoking, or exposure to second-hand tobacco smoke
  • Significant alcohol consumption (more than a glass a day for women or more than two glasses a day for men)
  • Lack of physical activity
  • Obesity
  • Poor eating habits, including a diet high in meat, fat and/or processed foods
  • Sun exposure, or other exposure to ultraviolet light (such as from tanning beds)

Risk factors you can’t control

Still, there are other risk factors that can’t be controlled. The greatest of these is aging. The older we get, the greater the risk of developing cancer. Other uncontrollable factors include:

  • Previous cancer diagnosis
  • Family history of cancer
  • Infections or viruses, such as helicobacter pylori (H. pylori) infection, Epstein-Barr virus (EBV, mononucleosis or “mono”) and human papillomavirus (HPV)
  • Genetics or inherited cancer syndromes, such as Lynch syndrome, or inherited mutations such as BRCA1 or BRCA2 
  • Weakened immune system, including from autoimmune diseases such as rheumatoid arthritis or lupus, and inherited immune disorders, such as Wiskott-Aldrich syndrome
  • Certain prescribed drugs, such as methotrexate or TNF inhibitors, hormone replacement therapy or immunosuppressive drugs used after organ transplants
  • Medical conditions, such as diabetes or chronic inflammation

Environmental factors

Environmental factors may also play a role in cancer. Sunlight or ultraviolet light exposure is a major environmental risk factor, though it’s one that may be lessened through use of sunscreen and the covering of exposed skin when outside.

Other environmental factors include:

  • Radiation exposure, including from radiation therapy for cancer treatment or from nuclear or industrial sources
  • Chemical exposure, including carcinogens from asbestos, radon, pesticides, fertilizers, herbicides, insecticides and toxins such as vinyl chloride or polychlorinated biphenyls (PCBs), or from working in the coal, metal or rubber industries

Questions for your care team

Your doctor or care team may have a wealth of information about cancer and how it may affect you personally. Don’t be afraid to ask questions and alert your doctor to any new symptoms you may be experiencing. Some questions that may help the conversation include:

  • Which cancer risk factors do I have, and how do they affect my risk of getting cancer?
  • Are there things I can do to lower my risk of getting cancer?
  • Which cancer screenings should I undergo, and how often? Are there any that should be done right away, such as a mammogram or colonoscopy?
  • Are there specific conditions or diseases in my family’s health history that may increase my risk?
  • Would I benefit from genetic testing?
  • What should I do if I become aware of a new risk factor, such as a close family member developing cancer?