This won't really answer your question, but...
I am 3 months out from chemo, for breast cancer. I went to an AME last week for BasicMed, and said something like, "Yeah, I know I'd never get the 3rd class, what with the cancer and all..." and the AME shrugged and said something like "Well, you COULD, it's just that you'd have to send the FAA stuff that they ask for, and it might take a few months."
I didn't inquire any more, since I'm content with BasicMed for now. And I don't know if colon cancer is seen any differently than breast cancer (or how the treatments differ, etc.) And mine was less than stage 3, but this AME didn't ask about the stage.
But this suggests that you should find an AME and schedule a "consult" -- that is, a chance to ask the question "what will the FAA require?" without actually doing the MedXpress thing -- because it may turn out to be easier than things sound when you read them on the FAA website. The only way to know is to ask.
Hope that helps,