A just-published article demonstrates that CT colonography is a good test for Medicare-age patients.
From the July 2012 issue of the American Journal of Roentgenology: "CT Colonography of a Medicare-Aged Population: Outcomes Observed in an Analysis of More Than 1400 Patients"
CT colonography is an excellent way of detecting early colon cancer (or excluding it), without the risks of a traditional colonscopy.
BTW, this is another medical test that President Obama was able to receive, but which many ordinary Americans with government medical insurance cannot: "President Obama Gets Virtual Colonoscopy (CT Colonography) But Medicare Denies CTC Coverage to Seniors".
(Related: "Is President Obama's Prostate Gland More Important Than Yours?", Forbes, 7/5/2012)