Narrator: Most cancers in their early, most treatable stages don't exhibit any symptoms. Colon cancer might be prevented if polyps that lead to the cancer are detected and removed.

Dr. Ernest Hawk of the National Cancer Institute's Cancer Prevention Division describes the tests that are used to detect colon cancer beginning at age 50.

Dr. Ernest Hawk: The first of them is probably the most well-proven and that's fecal occult blood testing, or looking for blood in the stool. Both polyps, as well as cancers, can bleed and you can identify that by doing a special test that's done at home. The results are given to your physician and we know that the use of that test can result in about a 30% reduction in colon cancer deaths. So that test is relatively convenient -- that is, it doesn't require any special procedures -- but some people are not particularly attracted to the methods that are involved.

Narrator: Another test is a flexible sigmoidoscopy which is an examination of the rectum and lower colon using a lighted instrument.

Dr. Ernest Hawk: And they look at the last part of the colon. Can go in about 50 centimeters -- about a couple of feet -- and look at the lining, look for polyps, as well as cancer. That's another very effective method. So it requires going into a doctor's office, doesn't require any sort of anesthesia, but it takes 15 minutes or so.

The third option is a barium enema. That's an x-ray examination of the colon where you go into a hospital, typically, have an enema to clear out the colon. Subsequently, a radiologist takes you into the x-ray room, puts a dye into the colon and then takes x-ray pictures. That, again, takes half an hour or so. It has slightly less sensitivity -- it can't find polyps quite as well as some of the other tests -- but it's perfectly acceptable, as well as one of the several methods.

And lastly, there's colonoscopy where a physician takes a lighted tube and looks at the entire lining of the colon, several feet long. That procedure typically requires some amount of anesthesia so a doctor gives you medicine -- makes you a little bit drowsy. It takes about 15 minutes to half an hour. And that procedure -- its benefits really are that it can both identify cancers and polyps, but also treat those that are not complicated. So if a small, pre-cancerous growth polyp is identified, it can be removed in the same setting.

Narrator: Dr. Hawk says whatever test you and your doctor determine is right for you -- fecal occult blood test, sigmoidoscopy, barium enema, colonoscopy, or a combination of some of these -- if you are 50 or over, the important thing is to get tested.

Dr. Ernest Hawk: I think the big message is that people need to be screened. For any one of -- for any individual, each of those tests have plusses and minuses that are best decided in the context of the patient and the physician making the decision that's best for them. So I don't know that there's any one test that's better for seniors versus another. The important message is that you need to avail yourself of at least one of them.