1.   Her husband, Webb, just began participating in it, after doctors detected a precancerous polyp.

2.   For example, fecal occult blood screening looks for traces of blood in the stool that can indicate the presence of precancerous polyps.

3.   Some at high risk of colon cancer might change their diets and get screened more often to detect and remove precancerous polyps.

4.   The volunteers included healthy people, including some at high risk for colon cancer, as well as with those with precancerous polyps and colon cancer patients.

5.   But if the scan shows tumors or precancerous polyps, a traditional colonoscopy is needed to remove them.

6.   If the rectum is left, patients need frequent checkups to remove precancerous polyps.

7.   Sixty-two percent with advanced polyps in their upper colon showed no precancerous polyps in the lower section.

8.   While its exact cause remains unclear, it involves alterations in many genes over years and changes in the colon wall that let precancerous polyps develop.