There is no such thing as ageing, and cancer is not related to it.

Several separate cellular processes have to accumulate in a normal cell to alter it into the seed of a growing carcinoma. Even though cancer is much commoner in the old than in the young, there is no good evidence whatever that these separate processes have any systematic tendency to take place more readily among old than among young adults. (Indeed, there are some instances in which carcinogenic treatments actually elicit cancer less rapidly among the old!) There are obvious evolutionary reasons why substantial cancer risks should be delayed until the end of the usual lifespan, and it appears that this is achieved chiefly not by having the component processes of neoplastic transformation themselves particularly dependent on age, but simply by requiring not one, but several, of them en route from full normality to full malignancy, and by giving at least some of them an extraordinarily low daily probability. The daily probabilities of these separate events are, of course, under evolutionary influence, and some of them appear to have changed by orders of magnitude over the tens of millions of years of evolution that separate humanity from various short-lived animals.