2010-07-06 15:40:15 UTC

Preventing CRC in Underrepresented Minorities: Do Minority Populations Need Alternative Screening Strategies?

July 6, 2010

John M. Carethers, MD, AGAF

John M. Carethers, MD, AGAF

Professor of Internal Medicine, University of Michigan, Ann Arbor  


Colorectal cancer (CRC) is one of the most prevalent cancers in the U.S., affecting 146,970 persons in 2009, and is the second most common cause of cancer deaths (behind lung cancer) with 49,920 deaths in 2009.1 Key risk factors for CRC development are:

  • Age, with dramatic increases in CRC incidence after age 50 (this age is used to initiate screening due to the asymptomatic nature of CRC development in average-risk individuals).
  • Family or personal history, which puts the patient or relatives at risk for developing cancer at a younger age.
  • Environmental influences, such as consumption of meat and fat, which are epidemiologically linked to cancer development.
  • Inflammation, particularly in the colon from IBD.
  • Ethnicity and race.2

CRC screening can detect cancers at earlier stages or as precursor adenomas, and removal of these lesions as a result of screening improves the prognosis of patients who otherwise may have progressed to advanced disease. Current screening paradigms for CRC are based on age, with patients at higher risk (i.e., those with IBD and personal or family history of CRC) put into surveillance programs.3 There are no guideline considerations for environmental factors, which are difficult to measure, or ethnicity or race.

Principles for modification of current screening guidelines must include consideration for higher risk individuals. Screening should begin before the age of significant increases in cancer incidence for a group, and screening should be adjusted by the observed biology or epidemiology of risk group. This approach is followed for patients with familial adenomatous polyposis, Lynch syndrome and IBD, once they are recognized. Practitioners in general are less aware of the higher risk for CRC among ethnic or racial groups, but the same principles should be applied to these groups based on knowledge of the natural history and biology for those groups.4 For instance, in Ashkenazim, a specific missense mutation in the adenomatous polyposis coli gene (I1307K) doubles the risk for adenoma development and confers an increased prevalence of CRC.2

Blacks have the highest incidence and death rates for CRC among all major races or ethnicities in the U.S. (table), and have a higher proportion of CRCs under the age of 50 compared with whites (10.6 percent versus 5.5 percent).5 There is a higher preponderance of right-sided colon cancers in blacks,5, 6 perhaps predicted by a higher prevalence of right-sided adenomas greater than 9 mm in older blacks compared to whites,7 and blacks are more likely to present at later stages of disease.8 It is not clear to what extent genetic, dietary, lifestyle, socio-economic, genetic or preventative issues account for the differences detected in blacks. However, screening has been suggested to begin at age 45 years6 due to the higher prevalence of CRC below the age of 50 years, matching the prevalence of whites with CRC at the age of 50 years. This proposal has not been put into widespread practice, as this recommendation was omitted from the multi-society guidelines.3

Because of the prevalence of relevant right-sided polyps and cancer among blacks, colonoscopy is the recommended test of choice for this population6 over all other screening approaches outlined by the multi-society group.3 There is increasing indirect evidence that screening is reducing the incidence of CRC in the U.S.,1 but there are questions regarding colonoscopy on its effectiveness in reducing mortality in patients with right-sided cancers when used as a screening tool.9 Notwithstanding further evaluation on that point, colonoscopy is the same test recommended for other high-risk groups due to involvement of portions of the entire colon, and is the test that should be employed for blacks at the age of 45 years as a high-risk group with a higher prevalence of right-sided lesions. Any screening is better than no screening, and patients who either do not want colonoscopy or don’t have access to colonoscopy should be screened by the other recommended modalities3 that may reduce mortality from CRC as a backup measure to colonoscopy. Individuals, regardless of race or ethnicity, who reside in poorer communities with lower access to health care do not experience a reduction in CRC incidence compared to more affluent communities; this remains a key barrier to colonoscopy screening.10 This may hold true despite non-colonoscopic forms of screening because if any of these tests are positive, a colonoscopy is required for follow-up. However, practitioners should advocate the use of screening colonoscopy in blacks beginning at the age of 45 years.


1. Jemal A, Siegel R, Ward E, Hao Y, Xu J, Thun MJ. Cancer statistics, 2009. CA Cancer J Clin 2009;59:225-249.
2. Grady WM and Carethers JM. Genomic and epigenetic instability in colorectal cancer pathogenesis. Gastroenterology 2008;135:1079-1099.
3. Levin B, Lieberman DA, McFarland B, Andrews KS, Brooks D, Bond J, Dash C, Giardiello FM, Glick S, Johnson D, Johnson CD, Levin TR, Pickhardt PJ, Rex DK, Smith RA, Thorson A, Winawer SJ; American Cancer Society Colorectal Cancer Advisory Group; US Multi-Society Task Force; American College of Radiology Colon Cancer Committee. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. Gastroenterology 2008;134:1570-1595.
4. Carethers JM. Should African Americans be screened for colorectal cancer earlier? Nat Clin Pract Gastroenterol Hepatol 2005;2:352-353.
5. Carethers JM. Racial and ethnic factors in the genetic pathogenesis of colorectal cancer. J Assoc Acad Minority Physicians 1999;10:59-67.
6. Agrawal S, Bhupinderjit A, Bhutani MS, Boardman L, Nguyen C, Romero Y, Srinvasan R, Figueroa-Moseley C. Colorectal Cancer in African Americans. Am J Gastroenterol 2005;100:515-523.
7. Lieberman DA, Holub JL, Moravec MD, Eisen GM, Peters D, Morris CD. Prevalence of colon polyps detected by colonoscopy screening in asymptomatic black and white patients. JAMA 2008;300:1417-1422.
8. Ghafoor A, Jemal A, Cokkinides V, Cardinez C, Murray T, Samuels A, Thun MJ. Cancer Statistics for African Americans. CA Cancer J Clin 2002;52:326-341.
9. Baxter NN, Goldwasser MA, Paszat LF, Saskin R, Urbach DR, Rabeneck L. Association of colonoscopy and death from colorectal cancer. Ann Intern Med 2009;150:1-8.
10. Hao Y, Jemal A, Zhang X, Ward EM. Trends in colorectal cancer incidence rates by age, race/ethnicity, and indices of access to medical care, 1995-2004 (United States). Cancer Causes Control 2010 (in press).

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