The American Cancer society (ACS) has published its latest colon cancer screening guidelines. which can found here.
These are their current testing options:
Double-contrast barium enema (DC BE)
DC BE appears to be a dying art, the review mentions that as time goes by even fewer and fewer radiologists will be proficient in the procedure. There is little to recommend it ,in my view. The pre procedure purging is a bad as colonoscopy and if a shadow is seen that could be a polyp or mass, colonoscopy has to be done anyway. In the last 7 or 8 years, I have not heard of anyone screened by this procedure except one of my class mates who is a radiologist.
Flex Sig if done to the splenic flexure ( or about the 40 cm. level)at best may be 60 to 70% as sensitive as colonoscopy. However, older patients and Afro-American patients are said to have a higher prevalence of proximal lesions so that in those groups even more cases of colon cancer will be missed. Plus you don't get any Versid.
CT colonography apparently has improved to the point that the ACS panelists have elevated it to prime time. Again as with the DC BE, the prep is as bad as the colonoscopy prep and if there is a positive finding the patient needs a colonoscopy as well.
My view is the bottom line (yeah, I know) is if you want to be screened optimally for colon cancer go with the colonoscopy. I have a bit of a family history of colon cancer and am getting that procedure every five years. The GI folks have tried various preps but the liquid diet for 1-2 days and then Golytely or Nulytely (both contain PEG 3350 and electrolytes) may be best. There is some risk of renal damage from some of the oral sodium phosphate solutions or tablets that were tried for a while in a effort to provide a less onerous bowel cleansing prep and you want to be sure that the endoscopy goes by the one- needle, one- syringe, one- vial one- patient rule which according to a recent report can have disastrous results if ignored.
The above reference from the ACS is very comprehensive and probably will tell you everything you wanted to know about this subject and more.