First, the problems that are associated with colonoscopies are almost never allergic reactions. Second, a colonoscopy will catch cancer way way more than 40% of the time. Third, when a colonoscopy overlooks or misses colon cancer, no other test will be able to show it. And I will tell you with 100% certainty that more often than not cancerous cells are not overlooked. I would look more closely at the sources you are reading about this information. Many times a study like this that you might be reading was not done on a randomly selected group of individuals so the results are biased. Also, a CEA test is usually only done to monitor people who already have colon cancer, so I'm curious why you had one done (what symptoms are you having).
To answer your question. There are safer less invasive tests. However, they are much less accurate. These tests will only show polyps. If a polyp is found then you need a colonoscopy to biopsy them. These tests include a barium enema, a CT scan, or the camera pill. So either you have a polyp shown on the other tests and then you will need a colonoscopy or you won't have a polyp shown on the other tests and then you will need a colonoscopy because those other tests aren't accurate.
Colonoscopies save many many more lives than the few amount of people that have problems from them.
Thank you for your input, I do live in the US and I do not believe all the half truths we are told about the safety of a test that has caused multitudes of allergic reactions and other well kept secret reactions. More often than not cancerous cells are over looked and/or missed completely. I am really looking for the answer to my original question, is there another safer less invasive test?
Welcome to the gastroenterology community! Where did you get your information about the dangers of a colonoscopy and the 40% accuracy rate? Colonoscopies are very safe and are much much more accurate that other tests (like the camera pill or CT scan or barium enema). I see you live in the US and are 70 years old and in the US, everyone over 50 is supposed to get a colonoscopy even if they aren't having any symptoms.