One of the consequences of an aging immune system is that it stops removing senescent cells - certainly, senescent cells increase dramatically with age. Here is a look at why that process is likely to increase your cancer risk: "Although 'cellular senescence' can suppress tumor formation from damaged cells by blocking the cell division that underlies cancer growth, it has also been implicated in promoting cancer and other age-related diseases. To understand how this might happen, we measured proteins that senescent human cells secrete into their local environment and found many factors associated with inflammation and cancer development. ... Senescent cells promote the growth and aggressiveness of nearby precancerous or cancer cells ... Our findings support the idea that cellular senescence can be both beneficial, in preventing damaged cells from dividing, and deleterious, by having effects on neighboring cells; this balance of effects is predicted by an evolutionary theory of aging." Senescent cells are a prime target for the same sorts of discerning therapies being developed to kill cancer cells with no side-effects.

Link: http://dx.doi.org/10.1371/journal.pbio.0060301