COMMENTARY

Highlights of the 2009 Colon Cancer Screening Guidelines From the American College of Gastroenterology -- What You Need to Know

David A. Johnson, MD, FACG, FASGE, FACP

Disclosures

May 20, 2009

American College of Gastroenterology Guidelines for Colorectal Cancer Screening 2008

Rex DK, Johnson DA, Anderson JC, Schoenfeld PS, Burke CA, Inadomi JM
Am J Gastroenterol. 2009;104:739-750

This is an update to the guidelines issued in 2000, when the American College of Gastroenterology (ACG) was the first organization to endorse colonoscopy as the preferred strategy for screening and prevention of colorectal cancer (CRC). The updated guidelines were developed following a systematic review of the English-language peer-reviewed literature.

In contradistinction to other CRC national guidelines which have offered a host of options, in the updated guidelines the ACG elected to provide specific recommendations, all of which were assessed using the GRADE system to provide the strength of evidence supporting each recommendation. This system evaluates the methodologic quality of the evidence, the benefits and risk, and the implications for application to patients. The testing methods for CRC were divided into cancer prevention and cancer detection tests. Cancer prevention tests (which detect precancerous polyps and facilitate removal before cancer develops) are preferred over cancer detection tests.

All care providers involved in CRC screening will want to review these new recommendations to provide the best guidance to their patients. Highlights of the guidelines:

1. Colonoscopy is the preferred CRC prevention test. Colonoscopy every 10 years beginning at age 50 remains the preferred strategy for CRC screening. Alternatives for patients who decline colonoscopy are flexible sigmoidoscopy or computed tomography (CT) colonography (see #4).

2. Screening for black persons should begin earlier. The updated guidelines include a new recommendation to begin CRC screening in black persons at age 45 because of the high incidence of CRC and a greater prevalence of proximal or right-sided polyps and cancerous lesions in this population.

3. New recommendations for bowel preparation aim to enhance effectiveness and improve tolerability for patients. To improve the quality of colonoscopy exams and the tolerability of bowel preparation, the ACG believes that the best method of bowel preparation is "split dosing," whereby the patient takes at least half of the preparation on the day of colonoscopy rather than the entirety of the preparation on the day before the examination. Another new recommendation is that patients be allowed to ingest clear liquids until 2 hours prior to sedation for colonoscopy, consistent with practice guidelines of the American Society of Anesthesiologists.[1]

4. CT colonography (also known as virtual colonoscopy) performed every 5 years is endorsed in the updated ACG guidelines as an alternative to colonoscopy performed every 10 years in patients who decline the traditional modality. The ACG included CT colonography as an alternative in light of recent studies which revealed that this test has a 90% sensitivity for colon polyps ≥ 1 cm. Despite its recommendation, CT colonography does have notable limitations. It is not considered to be equivalent to colonoscopy as a screening strategy because of its inability to detect polyps ≤ 5 mm, which constitute 80% of colorectal neoplasms, and because false positives are common with CT colonography. Additionally, there are significant concerns about the radiation risk associated with even a single test, and more so for repeated CT colonography studies, although the exact risk associated with radiation is unclear.

5. Barium enema is not recommended for CRC screening/prevention. The ACG no longer recommends this test as an alternative to CRC screening because the quality of performance is variable given the few remaining centers that are able to achieve high-quality testing with this somewhat dated imaging technique.

6. Fecal testing is categorized as a cancer detection test, not a cancer prevention test. Fecal immunohistochemical testing (FIT) replaces the older guaiac-based fecal occult blood test and is recommended as the preferred cancer detection test (performed annually). FIT has superior performance characteristics compared with older guaiac-based Hemoccult II® cards, with a comparative doubling in the detection of advanced lesions and little loss of positive predictive value. Additionally 10% and 12% gains in adherence with FIT were documented in the first 2 randomized controlled trials comparing FIT with guaiac-based testing.

7. Screening recommendations related to family history have been updated. The major change in the new guidelines is that an increased level of screening is no longer recommended for those with a history of adenomas in a first-degree relative or in patients ≥ 60 years of age with colon cancer or advanced adenomas. The new guidelines recommend the following:

  • Single first-degree relative with CRC or advanced adenoma (adenoma ≥ 1 cm in size, or with high dysplasia or villous elements) diagnosed at age ≥ 60 years: Recommended screening is the same as for those at average risk (colonoscopy every 10 years beginning at age 50 years).
     

  • Single first-degree relative with CRC or advanced adenoma diagnosed at age < 60 years or 2 first-degree relatives with CRC or advanced adenomas: Recommended screening is colonoscopy every 5 years beginning at age 40 or at 10 years younger than age at diagnosis of the youngest affected relative.
     

  • Single first-degree relative with only small tubular adenoma is not considered to increase the risk for CRC, and no changes beyond average-risk screening are needed.
     

  • Modification of the above-cited screening approach should be made according to family histories of colorectal polyps and cancers that are suggestive of hereditary nonpolyposis colorectal cancer (HNPCC). The recommendation is to begin screening these individuals at age 40 or at 10 years younger than age of onset in the youngest first-degree relative.

8. Key emphasis should be on quality of colonoscopy. Colonoscopies should be performed by appropriately trained and skilled examiners who are dedicated to consistent performance of high-quality examinations. Specific measures for improving the quality and cost-effectiveness of colonoscopy were also highlighted:

  • Cecal intubation should be documented by description of landmarks and photography.
     

  • All colonoscopists should document adenoma detection rates. The target for detection on screening exams for patients (≥ 50 years) should be at least 25% in men and 15% in women.
     

  • Withdrawal times (measured from the cecum) should average at least 6 minutes in intact colons in which no biopsies or polypectomies are performed. This has greatest relevance to colonoscopists with low adenoma detection rates.
     

  • Polyps should be removed by effective techniques, including snaring (rather than forceps methods) for all polyps > 5 mm in size.
     

  • Piecemeal resection of large sessile lesions requires close follow-up.
     

  • In patients with complete examinations and adequate preparation, recommended screening and surveillance intervals should be followed.

9. Obesity is highlighted as a risk factor for colon neoplasia. A consistent body of evidence supports the concept that both overweight and obese status are associated with increased risk for CRC. The risk for CRC in obese compared with nonobese patients is increased 1.5- to 2.8-fold. The pattern of fat distribution is important because it relates to the reported CRC risk. Abdominal obesity is a stronger risk factor than truncal obesity or body mass index. Obesity is also associated with presence and size of colon adenomas. Overall, obesity approximately doubles the relative risk for adenomas, and obesity is particularly associated with high-risk adenomas (≥ 1 cm, tubulovillous). The guidelines do not recommend earlier screening but instead more emphasis on ensuring that these patients are appropriately screened.

10. Issues related to smoking as a risk factor for colon neoplasia are addressed. The literature reveals that people with a smoking history of more than 20 pack-years have greater than 2-3 times the risk for colorectal adenomas vs nonsmokers. Male and female smokers have as much as a 30% increased risk for colon and rectal cancer as well as up to a 50% increased risk for death from CRC. It has also been observed that the risk for CRC and related mortality may be increased after ≤ 20 pack-years of smoking exposure. The impact of quitting is not yet clear, but it appears that the risk may continue to increase as long as 20 years after smoking cessation. The guidelines do not recommend earlier screening but instead more emphasis on ensuring that these patients are appropriately screened.

Abstract

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