How did I get cancer?

Although every patient and family member wants to know the answer to this question, the reason people develop cancer is not well understood. There are some known carcinogens (materials that can cause cancer), but many are still undiscovered. We do not know why some people who are exposed to carcinogens get cancer and others do not. The length and amount of exposure are believed to affect the chances of developing a disease. For example, as exposure to cigarette smoking increases, the chance of developing lung cancer also increases. Genetics also plays an important role in whether an individual develops cancer. For example, certain types of breast cancer have a genetic component.