The American Cancer Society (ACS) estimates that nearly 1.5 million new cases of cancer will be diagnosed in the United States in 2007. Age is a primary risk factor for the disease with about 77 percent of all cancers being diagnosed in people age 55 and older. As of 2004, there were approximately 10.8 million men and women living with a history of cancer.

The association between age and an increased risk of cancer is not well understood. Certain changes in the cells cause cancer to begin, but scientists cannot explain the reasons for the process. Despite several theories, there is no definitive explanation for why cancer occurs more frequently in the older population.

Researchers continue to explore the association between aging and cancer risk. Meanwhile, healthcare providers urge people to undergo various cancer screening procedures as they grow older. The ACS has established age and frequency guidelines for various tests that can help screen for cancer in people at average risk of getting the disease.