Yes, dogs can get colon cancer. But, until it is diagnosed, many things can scare us that are not, in fact, cancer. Please get this diagnosed by a vet - there may be no reason to be worried. I hope that is true.
If not... then sadly, there is really no way to answer your question in a helpful manner. So much depends on the age of your dog, breed/mix, how far along the cancer is and more.
It is an important question because "success" in canine cancers is sometimes measured in months, not years. Getting the information from a vet on what is likely for your dog with a specific cancer at a specific stage can help anyone figure out next steps.
Here are a few links to help you sort out things out:
Again, I hope that these is nothing here to worry about.