There are many people with many types of cancers that NEVER have it come back. I don't think once you have been DX that it ever completely leaves your mind on the possibility of it coming back. However, as many have stated it is more likely that those with this type of cancer will die from something else. I am currently 10 years free as mine was caught early and treated accordingly. I choose to go forward as much as I can taking one day at a time.
I have read a Johns Hopkins theory that cancer possibly manifests itself 4-5 times in one's life and it is often gets beaten back with our immune system. It is stress and breakdown of our system that lets this disease continue. I have no idea if this is right as it is just a theory. Eat well (everything in moderation and nothing to excess), get plenty of exercise, maintain a good weight, keep your checkups and don't smoke and you have done most of what you can control. The rest I leave to a Higher Authority and simply don't worry about something that may never happen again.
