How will having colon radiation affect my long-term health?

Unlikely to affect.: Radiation to the colon typically will not affect long-term health. On rare occasions there can be chronic changes in bowel habits such as diarrhea, or scar tissue can form which has the potential to cause a mechanical obstruction.

Varies: Depends on the side effects you experience. It may be very bothersome later on if radiation colitis (colon) or proctitis (rectum) develops, which can be very irritating and annoying with its attendant diarrhea. Fortunately, the vast majority of patients have little if any long lasting side effects.