Definition

A measure of the risk that a certain event will happen during a person’s lifetime. In cancer research, it is usually given as the likelihood that a person who is free of a certain type of cancer will develop or die from that type of cancer during his or her lifetime. For example, a woman with no known risk factors for breast cancer has a lifetime risk of developing breast cancer of about 12%. This means one out of every eight women will develop breast cancer during her lifetime.