Cancer is actually a group of many related diseases. It can occur at any age, although it is more common after age 40. The exact causes of cancer have yet to be proven. But researchers do know that cancer is linked to personal habits, such as smoking, drinking alcohol and poor diet. It also is linked to environmental factors, including ultraviolet sunlight, chemicals in air pollution and elsewhere, and occupational hazards such as overexposure to x-rays and industrial chemicals like asbestos.
Some types of cancer seem to track in families.
In America today, half of all men and one-third of all women will develop cancer during their lifetimes. More than eight million people are living with cancer today or have been cured of the disease. The sooner a cancer is found and treatment begins, the better the chances of a cure. A risk factor is anything that increases a person's chance of developing a disease such as cancer. Different cancers have different risk factors.