Yes, and one of the hallmarks of cancer is a removal of the usual DNA damage checkpoints. Cells have sensors that detect damaged DNA and stop cell division, and once that is gone evolution happens on an extremely accelerated times scale. In lung cancer, for example, we have developed entire series of drugs to go after successive resistance mutations inside the EGFR gene.

When we first started getting good at sequencing the DNA of tumors, I remember initial reports of taking samples across the 3D space of a tumor and finding great spatial heterogeneity in the tumor genomes.

I'm actually most excited for using this drug in combination with colon cancer, where KRAS mutation is a common drug resistance evolution in response to drugs that target the gene EFGR (though cancer researchers may all have their favorites to go after, colon cancer went after my family especially hard).

Absolutely, this is selective pressure at work on cells with malregulated genetics. Most typically, this is in the form of drug efflux pumps, but you can definitely get more specific resistances.

Ways to avoid specific resistance include multiple treatments simultaneously, since the probability of generating resistance to both is the product of the probability of resistance either.

evolution is a wrong concept to approach it. cancer is not a separate life form, but a bug in the regeneration system of a complicated life form. it doesn’t exist outside of it, it cannot propagate.

thats environmental evolution...what happens here is cell "evolution" within a specific body