Age distribution of cancer in mice: the incidence turnover at old age.

We have studied cancer incidence in mice as a function of age in those cohorts where the rodents are allowed to live very close to their full natural lifetime. We find that the incidence rises as a function of age, but then flattens and turns over at an age of about 800 days. This behaviour is similar to that which we observed (Pompei and Wilson, 2001) in the Surveillance, Epidemiology, and End Results (SEER) data where the age distribution of human cancer incidence turns over at about age 80. Although other fits are possible, the three-parameter beta function model fits both the mouse data and the human data well. The beta model implies, and the data do not deny, the interpretation that cancer is not a certainty and mice may also outlive their cancers, although high-dose cohort results suggest cancer might be certain if dose is sufficiently high. Limited data suggest that the cancer age distribution, including the turnover, may be time shifted by dietary restriction.