The influence of an aging immune system on cancer incidence and progression.

The majority of cancers occur in patients over the age of 65 years, and yet the important interactions of normal aging upon the neoplastic process remain to be thoroughly explored. For example, there is no unifying and conclusive explanation for the increased risk of cancer with advancing age. The age-associated decline in immune function has previously been implicated in this regard. However, it is likely that other factors, such as the time it takes to proceed through the multistep neoplastic process, and the combined influence of age-associated increased susceptibility to carcinogen and decreased DNA repair are more important. Nevertheless, immune senescence does influence various aspects of tumor growth and spread. In this article these aspects are reviewed.