Does colonoscopy prevent colon cancer?

Likely. Cancers start as polyps. Removing polyps decreases cancer risk, but no test guarantees finding every polyp.
Colon cancer. Colonoscopy prevents colon cancer hence it is recommended as screening test at age 50 for people with average risk and age 40 if there is family history.

Related Questions

Some steps you can take to prevent colon cancer besides frequent colonoscopy?

Be healthy. Eat healthy low fat foods, high in fiber, fruits and vegetables. Avoid a lot of meats and fats. Maintain a healthy weight, and be active or exercise. Use of vitamin d and Aspirin has been under review as possible preventative measures to discuss with your doctor. Colonoscopy does not prevent cancer, but can remove pre-cancerous growths or polyps and can locate early tumors. Read more...
DIet Exercise. Regular exercise. Eat healthy. Less fat in the diet. Limit processed meats, fish and poultry rather than red meats. Lots of fruits and vegetables. Avoid obesity. Read more...

Might it be that a colonoscopy prevents colon cancer, or is it simply a screening tool?

Yes it can. Colonoscopy is done to look for polyp which are precursors of cancer. So if the polyp is removed before it becomes cancerous, then we have prevented development of colon cancer. Read more...

Would it be possible to develope colon cancer large enough for blockage 5 years after an all clear colonoscopy?

Sometimes. Unfortunately yes. Some less common cancers have very rapid doubling times. And can grow quite large. A left colon cancer is more likely to obstruct than one on the right. Read more...

Why is it you hear about people who had squeaky clean colonoscopies only to have full blown colon cancer two years later?

Lynch syndrome. A majority of folks who will get colon cancer have some benign polyps first. Someone carrying of of the lynch family of mutations is likely to get colon cancer out of the blue, with no preceding polyp. You're still smart to get 'scoped every so often, and people known to the lynch's get scoped perhaps yearly. Read more...
Sometimes. There are flat lesions that can be missed on colonoscopy and there are also rapidly growing tumors to explain this. Read more...

Is it recommended to get a colonoscopy at age 43 if there is a family history of colon cancer? What other tests are needed at this age?

Yes...get one done. The age depends on your family, history. Screening mammography, a complete family history may add genetic testing. A complete physical. Read more...
10 years before diag. A basic guideline is that in the case of a potentially inherited cancer trait, that we start screening 10 years before the presentation of a first degree relative, i.e. Parent or sibling. If the relative was diagnosed with colon cancer at age 53, we consider beginning screening tests at 43. Otherwise begin screenings as age appropriate, colonoscopy age 50, mammo age 40. Read more...