I had 37 external beam radiation treatments for a PC recurrence at age 78. Knowing that I couldn't have a colonoscopy for a year after radiation, I wanted one before. Three doctors refused because I had a colonoscopy three years earlier. I finally found a doctor to do it and he removed three pre cancerous polyps. A year after the radiation I had another colonoscopy, which found three more polyps, including a 1 1/2" polyp which must have been missed in the previous colonoscopy...it was too big to grow in that time. It also was too big to remove with a colonoscopy and I had to go back for an EMR (endoscopic mucosal resection). Because I get polyps so often, I now have to get colonoscopies annually. Bottom line--colonoscopies aren't fun but a day or two of discomfort sure beats dealing with colon cancer. Most people don't need them annually but it's a good idea to at least get one before radiation with a very experienced doctor. Fortunately, my PSA is now undetectable. I have my annual colonoscopy in three weeks.