Risk factors

Doctors often cannot explain why one person develops cancer and another does not. But research shows that certain risk factors increase the chance that a person will develop cancer. These are the most common risk factors for cancer:
Growing older
Tobacco
Sunlight
Ionizing radiation
Certain chemicals and other substances
Some viruses and bacteria
Certain hormones
Family history of cancer
Alcohol
Poor diet, lack of physical activity, or being overweight
Many of these risk factors can be avoided. Others, such as family history, cannot be avoided. People can help protect themselves by staying away from known risk factors whenever possible.
If you think you may be at risk for cancer, you should discuss this concern with your doctor. You may want to ask about reducing your risk and about a schedule for checkups.
Over time, several factors may act together to cause normal cells to become cancerous.