I had a colonoscopy in Aug 2023, 3 mos after completing 37 IMRT salvage radiation treatments in May 2023.
No problems at all. I did advise the Gastroenterologist of my radiation treatment before the procedure and he reported no indication of any radiation treatment damage to my colon. I was particularly concerned because I had very bad radiation proctitis the second half of my radiation treatment, all symptoms resolved 2 - 3 weeks after radiation completed and it was reassuring to get a good report from the colonoscopy
Best wishes.