[cyberax]

Sure. But in general, cancer risk should scale with the number of cell divisions, which is fairly low for mice. And other small, short-lived mammals like weasels are not as susceptible to cancer. Naked mole rats (also rodents!) are downright cancer-proof.

This all means that mice don't have a good natural cancer-suppression machinery, and this in turn makes them somewhat awkward to use to discover new treatments.