This study does seem to explain why cancer that seems chemo-resistant sometimes returns after chemo.
Cancer will be about as chemo-resistance as the rest of your fast cell reproduction processes. The lining of the digestive tract will be hit hard but will recover. Similarly cancer will get hit hard and will recover. This applies to all types. However if you are lucky (and this is where modern medicine completely fails), your own immune system will be able to fight off the remaining cancer and prevent regrowth.