[howbadisthat]

Cancer tends to have an interesting relationship with cellular protein transport. And as a consequence has problems dealing with heat. The protein transport mechanism by which immune surveillance is conducted is shared with cells surviving heat increases via ejection of heat shock proteins.

I once tried to find if there were any studies about incidence of cancer plotted against incidence of high fever in the same individuals but wasn't able to find anything. It may also point to the incidence of cancer actually rising due to suppression of other diseases.

This is plausible due the fact that diseases are a constant in nature and therefore evolution would take their presence as a given as much as the seasons or the sun. It would be very unfortunate if numerous anti-cancer adaptions simply haven't evolved because regular fevers took care of those cancer precursors.