A recent release from the american cancer society suggests that less than half of adults have received a colonoscopy, and its becoming evident:

And their avoidance is taking a toll: roughly three of five colorectal cancer diagnoses are being made at the later stages of the disease, when cure rates range from 10 to 67 percent.

I wrote last year that compliance with colon cancer screening continues to be low, and gave various options patients can discuss with their physician:

It is recommended by most organizations that people at average risk should start screening for colon cancer start at age 50. Those with a first-degree relative who has had colon cancer or an adenomatous polyp should start at age 40.

There are several options that can be discussed:
1) fecal occult blood test (FOBT) every year, with a colonoscopy if positive;
2) flexible sigmoidoscopy every 5 years;
3) FOBT + flexible sigmoidoscopy, FOBT should be done first because a positive result is an indication for colonoscopy, obviating the need for sigmoidoscopy;
4) colonoscopy every 10 years;
5) double-contrast barium enema every 5 years.

("Colorectal Cancer - A Colonoscopy Is The 'Gold Standard' For Early Detection", Medical News Today, Jul.25; Kevin, M.D., Sept.30, 2004)