Some kinds of cancer are caused by things people do. For example, smoking causes cancers of the lungs, mouth, throat, bladder, kidneys and some other organs, as well as heart disease and stroke. While not everyone who smokes will get cancer, smoking increases a person's chance of getting the disease. Drinking a lot of alcohol has also been shown to increase a person's chance of getting cancer of the mouth, throat, and some other organs. This is especially true if the person drinks and smokes.

Radiation (x-rays) can cause cancer. But the x-rays used by the doctor or dentist are safe. Too much exposure to sunlight without any protection can cause skin cancer.

Certain inherited DNA changes can increase the risk for developing some cancers and are responsible for the cancers that run in some families. For example, the BRCA genes (BRCA1 and BRCA2) are tumor suppressor genes -- they keep tumors from growing. Changes (mutations) in these genes can be passed on (inherited) from parents. When they are mutated, they no longer suppress abnormal growth, and cancer is more likely to develop.

But in most cases, the exact cause of cancer remains a mystery. We know that certain changes in our cells can cause cancer to start, but we don't yet know exactly how this happens. Many scientists are studying this problem.

Last Medical Review: 02/24/2009
Last Revised: 02/24/2009