Colorectal Cancer Screening: 45 is the New 50 - Annals of Internal Medicine: Fresh Look Blog


Wednesday, April 21, 2021

Colorectal Cancer Screening: 45 is the New 50

Robust health campaigns have succeeded in the positive association between colonoscopies and turning 50 years old in the general population. Although successful screening efforts have led to declining colorectal cancer (CRC) incidence and mortality rates in the older than 50 years age group, rates have increased in those younger than 50 years. The American Cancer Society (ACS) recommended lowering the screening age from 50 to 45 years in May 2018 to address this concern. The American College of Gastroenterology (ACG) recently published new CRC screening guidelines, recommending initiation of CRC screening at age 45 years (1). The U.S. Preventive Services Task Force, the U.S. Multisociety Task Force on Colorectal Cancer, and the American College of Physicians still recommend that CRC screening start at age 50 years. However, Bretthauer and colleagues (2) in their Annals.article “Colorectal Cancer Screening in Young Adults: About Carcinoid Tumors and Cancer” raise many of the commonly quoted concerns against adopting earlier screening. It is important to look beyond the numbers and put this issue in the relevant clinical and public policy context to make sense of the earlier screening recommendation.

Concern 1: The risk for CRC is overstated in the 40 to 49 year age group.
The ACS recommendation is conditional, or grade B, based on both modeling and SEER (Surveillance, Epidemiology, and End Results) data. The incidence of CRC in 45 year olds in 2014 to 2015 was similar to that in 50 year olds in 1992 to 1993, which preceded CRC screening as we now know it (3). Life-years lost due to CRC were similar in the 45 to 49 year and 50 to 54 year age groups (4). In addition, modeling has improved since earlier screening recommendations, and there is clearly strong evidence to support that CRC incidence among younger adults is a real, rather than artifactual, concern. Many have conjectured that detection bias due to increased screening has led to the increase of CRC seen in younger adults. However, late-stage CRC is increasing in younger adults at a rate much higher than seen in early-stage CRC (5-7).

Seventy-five percent of all CRC in younger adults is diagnosed in persons 40 to 49 years old (8, 9). Colorectal cancer in those younger than 50 years accounts for 11% of all male and 10% of all female CRC cases (3, 5). Younger adults are also more likely to present with more advanced disease than older adults. Although Bretthauer and colleagues (2) correctly state the absolute incidence of CRC is low in the younger age group, this fails to capture the nuance of a much more aggressive phenotype of CRC in younger persons. This cannot and should not be ignored in favor of bland statistics.

Concern 2: Increased screening is associated with increased risks.
Bretthauer and colleagues (2) propose that increasing colonoscopy rates will increase procedure-related mortality. The proposed risk for death is 3 per 100,000 colonoscopies, which is already a very low number, reflective of the low-risk nature of this screening modality. Younger adults have especially low rates of complications, especially compared with older patients (10). I would suspect that the screening of younger adults would likely have a low, if not negligible, effect on colonoscopy-related morbidity and mortality.

Bretthauer and colleagues (2) also anticipate that the influx of more patients in the screening pool would overwhelm our medical resources and capability. On the basis of a 2012 survey (11), the United States can absorb an additional 10.5 million examinations. The younger cohort of patients will add more than 20 million new patients. This poses a real cost to society and could possibly divert screening resources away from underserved populations—that is, minorities and rural communities. Put into practical context, however, screening adherence rates are only up to 60% in the older than 50 years cohort, so the increase in resource use may be overstated (10). Adding a younger cohort may allow us to better use our endoscopic capabilities, screen more patients, and prevent more cancer. The best screening test is of course the one which gets done, so I am less inclined to be discouraged by an increase in the eligible screening population.

Concern 3: Is it worth it to screen younger adults?
The incidence of CRC in White persons younger than 50 years is similar to that of African Americans for the same age range (4). As the ACG recommends screening African Americans starting at age 45 years, this would support screening the general population at this same age. There are no dedicated observational studies or randomized trials looking at CRC screening in those younger than 50 years, so the real benefits of earlier screening cannot be assessed unless we “try it and see what happens.” Is it worth looking at before rejecting it outright? Absolutely.

However, at the end of the day, population statistics may have little to do with the individual patient on your examination table. When I see a 50-year-old patient in my office to discuss a screening colonoscopy, his or her risk for CRC doesn’t come down to just age. Other risk factors include male sex, family history, obesity, smoking history, diet, medication use, and race. So, rather than getting hung up on a screening guideline with a strict age cutoff, it is useful to keep this in mind while formulating a personalized approach to each patient.

Earlier screening will not only positively affect my patients who are younger than 50 years, but also those who are older than 50 years. Early screening increases awareness of CRC screening and will enhance discussions in the 50 years or older group. The natural life cycle of malignant transformation takes about 10 years (12), so we need to recognize the continuum of the benefits of early screening.

Prevention of CRC is the main goal of all gastroenterologists. Screening the younger population can benefit our patients by diagnosing aggressive types of cancer earlier and reducing CRC incidence and mortality in all age groups. It can also add a societal financial burden and negatively affect health disparities in CRC. The decision is a personal one, based on an open clinical discussion. As a practicing gastroenterologist, I follow the earlier screening guidelines proposed by the ACS and ACG because the burden of proof supports earlier screening, with the positive effects of increased screening outweighing the negative ones. The pros and cons need to be weighed by clinicians so that we can arm our patients with the right information. Consideration of individual risk factors, red flag symptoms, and clinic or facility resource management should be done along with analysis of the data we have.


  1. Shaukat A, Kahi CJ, Burke CA, et al. ACG clinical guidelines: colorectal cancer screening 2021. Am J Gastroenterol. 2021;116:458-479. [PMID: 33657038] doi:10.14309/ajg.0000000000001122
  2. Bretthauer M, Kalager M, Weinberg DS. Colorectal cancer screening in young adults: about carcinoid tumors and cancer. Ann Intern Med. 2021;174:263-264. [PMID: 33315472] doi:10.7326/M20-7244
  3. Siegel RL, Miller KD, Fedewa SA, et al. Colorectal cancer statistics, 2017. CA Cancer J Clin. 2017;67:177-193. [PMID: 28248415] doi:10.3322/caac.21395
  4. Wolf AMD, Fontham ETH, Church TR, et al. Colorectal cancer screening for average-risk adults: 2018 guideline update from the American Cancer Society. CA Cancer J Clin. 2018;68:250-281. [PMID: 29846947] doi:10.3322/caac.21457
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  6. Austin H, Henley SJ, King J, et al. Changes in colorectal cancer incidence rates in young and older adults in the United States: what does it tell us about screening. Cancer Causes Control. 2014;25:191-201. [PMID: 24249437] doi:10.1007/s10552-013-0321-y
  7. Siegel RL, Jemal A, Ward EM. Increase in incidence of colorectal cancer among young men and women in the United States. Cancer Epidemiol Biomarkers Prev. 2009;18:1695-8. [PMID: 19505901] doi:10.1158/1055-9965.EPI-09-0186
  8. Patel SG, Ahnen DJ. Colorectal cancer in the young. Curr Gastroenterol Rep. 2018;20:15. [PMID: 29616330] doi:10.1007/s11894-018-0618-9
  9. You YN, Xing Y, Feig BW, et al. Young-onset colorectal cancer: is it time to pay attention? [Letter]. Arch Intern Med. 2012;172:287-9. [PMID: 22157065] doi:10.1001/archinternmed.2011.602
  10. Levin TR, Zhao W, Conell C, et al. Complications of colonoscopy in an integrated health care delivery system. Ann Intern Med. 2006;145:880-6. [PMID: 17179057]
  11. Welch HG, Robertson DJ. Colorectal cancer on the decline—why screening can't explain it all. N Engl J Med. 2016;374:1605-7. [PMID: 27119236] doi:10.1056/NEJMp1600448
  12. Rex DK, Johnson DA, Anderson JC, et al; American College of Gastroenterology. American College of Gastroenterology guidelines for colorectal cancer screening 2009 [corrected]. Am J Gastroenterol. 2009;104:739-50. [PMID: 19240699] doi:10.1038/ajg.2009.104

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