If structural tests such as colonoscopy can prevent cancer, why not recommend only these tests?

These tests require bowel preparation and an office or hospital visit, and have various levels of risk to patients. They also have limitations, greater patient requirements for successful completion, and potential harms. The panel also recognized that some patients will not want to undergo an invasive test that requires bowel preparation, may prefer to have screening in the privacy of their home, or may not have access to the invasive tests due to lack of coverage or local resources.