[boas]

Yes, we induce pancreatic cancer in pigs, and then we try to treat the cancer.

One important question is why so many new cancer treatments are successful in mice and rats, but then fail in human trials. You could point to genetic differences between mice and humans, but I think another important factor is simply the size difference. Just like a scale model of an airplane won't fly the same way, there are also scaling laws in animals. Large animals have a lower metabolic rate (per kg), require lower drug dosing (mg/kg), have more defense mechanisms against cancer, and have differences in blood flow and many other variables. We suspect that cancer treatments that work in pigs will be more likely to also work in humans.

[stenl]

The size of the tumor likely makes a big difference too: a centimeter-sized lump contains 1000x more cells than a millimeter-sized one. It will contain 1000x more drug-resistant cells (given identical mutation rates). For example, a human brain tumor is likely to already contain hundreds of cells carrying a mutation for every amino acid in every protein. Thus for any inhibitor drug you try, hundreds of cells will already be resistant, and they will grow back the tumor in just a few months. That’s much less likely to be the case in a mouse tumor.

[techsin101]

You could also say that induced cancers are somehow different from naturally occurring cancers so treatments targeted toward 'artificial' cancers fail to work on real things.

[TeMPOraL]

Could be what GP says, could be what you say, but the only way to know for sure is to try and reduce the differences.