Colonoscopy Is a Better Choice Than FIT for Opportunistic CRC Screening

In Australia and some European countries, colorectal cancer (CRC) screening occurs in an organized or programmatic setting, usually funded by the national government. Organized screening commonly relies on fecal occult blood testing (FOBT) as the primary means of screening, and usually the fecal immunochemical test (FIT). FIT is a good option for these programs as it is inexpensive, outperforms the guaiac-based tests and has high specificity. These countries with organized screening programs often have limited resources for primary colonoscopy screening. FIT screening focuses colonoscopy resources on a high-prevalence population that benefits most from the therapeutic potential of colonoscopy. Several randomized trials comparing FIT to colonoscopy for endpoints of CRC incidence and mortality reduction are in progress.

In the U.S., there is some organized screening — particularly in large health plans like Kaiser1 — but most screening originates in the opportunistic setting. Opportunistic screening refers to the patient-physician office interaction in which the physician recognizes the need for and appropriateness of screening a particular patient, offers screening, orders the screening test and ensures that the test is followed up by colonoscopy if positive and repeated at the right interval if negative.

The high utilization of colonoscopy in population surveys suggests that this “colonoscopy first, fecal test second” approach has been the predominant approach to screening in the U.S. for some time.

In the opportunistic setting, colonoscopy has multiple advantages over FIT. First, a negative screening colonoscopy is good for 10 years. Few physicians have the systems in place to ensure that FIT occurs annually, and the rate of repeat FOBT falls off dramatically in the opportunistic setting.2 Given this issue, the relative single-time sensitivity of colonoscopy versus FIT becomes very important. On a per-participant basis, colonoscopy outperforms FIT for detection of advanced adenomas by a wide margin3 and is likely considerably better for cancer detection. Further, FIT is useless for the detection of serrated-class lesions,4 which account for 20-30 percent of CRC cases,5 probably because sessile-serrated polyps have few or no surface blood vessels.

Colonoscopy and FIT should be the key elements of perhaps all screening programs. The most relevant question is not whether one or the other is the best or only way to screen for CRC but is rather how the two tests will be presented to patients who are screening candidates. For approximately two decades in the U.S., most physicians have utilized the sequential approach to making the screening offer, in which colonoscopy is offered first and FIT (or perhaps another test) is offered to those who decline colonoscopy. The sequential method of offering screening has the advantage of both maximizing overall adherence as well as adherence to the most effective test (colonoscopy).6 The sequential approach has been advocated by the American College of Gastroenterology.7 The high utilization of colonoscopy in population surveys8,9 suggests that this “colonoscopy first, fecal test second” approach has been the predominant approach to screening in the U.S. for some time. Although screening in the opportunistic setting is often considered inferior to organized screening by experts, the U.S. has utilized this format – and usually by sequential testing based on colonoscopy first – to reach the world’s highest participation rates in screening and the world’s largest declines in colorectal cancer incidence and mortality (3 to 4 percent per year since 2000).10

There are at least two other legitimate approaches to offering screening in the opportunistic setting. One is the multiple options approach, in which two or more options are presented to patients along with the strengths and weaknesses of each test. Colonoscopy and FIT should likely both be discussed in this approach, and increasing the number of options discussed beyond two has little value.11 The other approach is the risk-stratified approach, in which colonoscopy is offered to patients who are estimated (based on modeling) to have a high prevalence of advanced neoplasia, while FIT is offered to patients estimated to have a low prevalence. Recent models of risk stratification have been relatively simple to apply and have performed well.12,13 A major disadvantage of both the multiple options and the risk-stratified approach is the greater need for primary-care physicians to develop and adhere to FIT quality measurements.

For example, the U.S. Multi-Society Task Force on Colorectal Cancer has recently recommended that at least 60 percent of patients offered FIT should complete the test, that the rate of returned FIT tests that cannot be processed by the laboratory should be less than 5 percent, and that at least 80 percent of patients with positive FITs should adhere to colonoscopy.14 Again, systems to measure and ensure these levels of adherence are not currently in place in the opportunistic-screening setting in the U.S.

The most important issue for the primary-care physician relying on colonoscopy for screening is identification of colonoscopists with high-level performance. Comparisons of FIT to colonoscopy reflect average colonoscopy performance, in which single-time colonoscopy beats single-time FIT by a wide margin among screening participants.3 High-level performance colonoscopy would surely beat single-time FIT by a very wide margin for detection of advanced adenomas and without doubt for detection of serrated lesions.4 In summary, sustained adherence to annual FOBT is poor outside the organized-screening setting. Although the long-term relative benefits and harms of colonoscopy and FIT are still unknown and under study, offering colonoscopy first — followed by FIT or another test to those who decline colonoscopy — has been enormously successful in the U.S. The opportunistic-screening setting widely in place in the U.S. is ideally suited to colonoscopy screening.

Dr. Rex has received honoraria from Boston Scientific; research support from Boston Scientific, Endochoice, Endo-Aid and Medtronic; and serves on the ASGE Governing Board.


1. Levin, T.R., Jamieson, L., Burley, D.A., et al. Organized colorectal cancer screening in integrated health care systems. Epidemiological Reviews. 2011; 33: 101-110.

2. Liang, P.S., Wheat, C.L., Abhat, A., et al. Adherence to competing strategies for colorectal cancer screening over 3 years. Am J Gastroenterol. 2016 Jan; 111(1): 105-14.

3. Quintero, E., Castells, A., Cubiella, J., et al. Colonoscopy vs fecal immunochemical testing in colorectal-cancer screening. N Engl J Med. 2012; 366: 697-706.

4. Imperiale, T.F., Ransohoff, D.F., Itzkowitz, S.H., et al. Multitarget stool DNA testing for colorectal cancer screening. N Engl J Med. 2014 Apr 3; 370(14): 1287-97.

5. Rex, D.K., Ahnen, D.J., Baron, J.A., et al. Serrated lesions of the colorectum: review and recommendations from an expert panel. Am J Gastroenterol. 2012; 107: 1315-29.

6. Senore, C., Ederle, A., Benazzato, L., et al. Offering people a choice for colorectal cancer screening. Gut. 2013; 62: 735-40.

7. Rex, D.K., Johnson, D.A., Anderson, J.C., et al. American College of Gastroenterology guidelines for colorectal cancer screening. Am J Gastroenterol. 2009; 104: 739-750.

8. Shapiro, J.A., Klabunde, C.N., Thompson, T.D., et al. Patterns of colorectal cancer test use, including CT colonography, in the 2010 National Health Interview Survey. Cancer Epidemiol Biomarkers Prev. 2012; 21: 895-904.

9. Sabatino, S.S., White, M.C., Thompson, T.T., et al. Cancer screening test use – United States, 2013. MMWR. 2015; 64: 464-8.

10. Siegel, R., Desantis, C., Jemal, A. Colorectal cancer statistics, 2014. CA Cancer J Clin. 2014 Mar- Apr; 64(2): 104-17.

11. Griffith, J.M., Lewis, C.L., Brenner, A.R.T., et al. The effect of offering different numbers of colorectal cancer screening test options in a decision aid: a pilot randomized trial. BMC Medical Informatics and Decision Making. 2008; 8: 4.

12. Imperiale, T.F., Monahan, P.O., Stump, T.E., et al. Derivation and validation of a scoring system to stratify risk for advanced colorectal neoplasia in asymptomatic adults: A Cross-sectional Study. Ann Intern Med. 2015 Sep 1; 163(5): 339-46.6.

13. Chiu, H.M., Ching, J.Y., Wu, K.C., et al. A risk-scoring system combined with a fecal immunochemical test is effective in screening high-risk subjects for early colonoscopy to detect advanced colorectal neoplasms. Gastroenterology. 2016; 150: 617-25.

14. Robertson, D.J., Lee, J.K., Boland, C.R., et al. Recommendations on fecal immunochemical testing to screen for colorectal neoplasia: a consensus statement by the US Multi-Society Task Force on colorectal cancer. Am J Gastroenterol. 2017 Jan; 112(1): 37-53.

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