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You can reduce the odds of developing cancer by changing one or more controllable risk factors. A risk factor is anything associated with a higher propensity to develop the disease. It is important to realize, however, that even people with no risk factors can develop a particular cancer.

Some risk factors can be within a person’s control. Examples of controllable risk factors include:

• Alcohol consumption
• Diet
• Lifestyle factors such as exercise or sexual behavior
• Smoking or being around others who smoke
• Weight

Other risk factors are beyond a person’s control, such as:

• Age
• Family history and/or genetics
• Gender—some cancers affect only one gender, while in others, incidence is higher for men or women
• Race
• Other medical conditions

Finally, some risk factors may be partially controllable, such as treatment in the past for other medical conditions, or chemical exposure that may be occupationally related.

The accompanying chart summarizes the known and suspected risk factors that have been studied to some degree for the major cancers listed. Overall, the most important controllable risk factors for cancer are:

1. Smoking. Smoking is implicated in 10 out of the 18 major cancers listed (55%).
2. Risky lifestyle (sexual behavior, sun exposure) or lack of exercise. Such factors are associated with 8 out of 18 cancer types (44%).
3. Weight. Being overweight or obese is a contributing factor in seven out of 18 cancer types (38%).

Risk Factors by Cancer

Who you are also affects cancer risk. Some cancers can develop only in a man (testicular, prostate) and some only in women (cervical, ovarian, and uterine). Eight other cancer types are more likely in one sex or the other. And racial or ethnic differences in predisposition occur in 12 out of 18 types.

Among the uncontrollable circumstances, family history or specific genes/genetic traits are a risk factor for 14 of the 18 types (78%). The presence of other medical conditions is implicated in 14 cancer types as well, but the medical conditions differ by type of cancer.