What are the the major changes to these guidelines compared with previous reviews?

One significant change is the grouping of colorectal cancer screening methods into those that primarily identify cancer and those that both detect cancer and precancerous polyps, with a preference for those tests that can both detect cancer and prevent it by detecting premalignant polyps, which can then be removed.

Another change is the panel’s recommendation that options for screening must be able to detect the majority of cancers present at the time of testing. This criterion is based on expert opinion, and the following considerations:

• First, recent evidence has revealed an unacceptably wide range of sensitivity among some gFOBT strategies, with some practices and tests performing so poorly that the large majority of cancers are missed at the time of screening.
• Second, a test like gFOBT that demonstrates poor test sensitivity, but good program sensitivity, depends on high rates of adherence with regular screening. However, many patients have only one test and do not return for annual programmatic testing, and there is a lack of systems to ensure or facilitate adherence with recommended regular screening intervals.

For these reasons, the panel concluded that physicians and institutions should select stool blood tests that have been shown in the scientific literature to detect the majority of prevalent colorectal cancers in an asymptomatic population. If there is not evidence that an available test has met that benchmark, it should not be offered to patients for colorectal cancer screening.

The panel also added two new tests as acceptable options: CT colonography every 5 years, and sDNA testing (for which the optimal screening interval is currently unknown).

Finally, the panel eliminated the previously recommended preference for a combined approach using gFOBT or FIT every year plus flexible sigmoidoscopy every 5 years; in the revised guideline flexible sigmoidoscopy every 5 years is sufficient without the addition of annual gFOBT or FIT.