A year old thread, but I'm going to bring it back to life.
My maternal grandmother had 18 inches of cancerous colon removed back in the late 70s. She lived to age 97 with no recurrence. My mother underwent surgery for colon cancer in 1995, but during the operation the doctors discovered that the cancer had spread into her liver; she passed away less than two years later.
I've had half a dozen colonoscopies since then, because of my family history. The only thing found has been a few polyps, which were removed during the procedure and before anything could develop.
Colonoscopies save lives. If your doctor recommends it, get 'er done. It's easy, and sure beats the alternative. I have two grandchildren that I have promised to be here for, and help grow up.