COMMENTARY

Colon Polyp Surveillance: Need-to-Know Changes

David A. Johnson, MD

Disclosures

December 14, 2012

Guidelines for Colonoscopy Surveillance After Screening and Polypectomy: A Consensus Update by the US Multi-Society Task Force on Colorectal Cancer

Lieberman DA, Rex DK, Winawer SJ, Giardiello FM, Johnson DA, Levin TR
Gastroenterology. 2012;143:844-857

New Guidelines on Postpolypectomy Surveillance

Guidelines from the Multi-Society Task Force (MSTF) on Colorectal Cancer (American College of Gastroenterology, American Gastroenterological Association, and American Society of Gastrointestinal Endoscopy) on postpolypectomy surveillance intervals after colonoscopy have recently been updated from the 2006 recommendations. New issues have emerged since the 2006 guideline, including risk for interval colorectal cancer (CRC), proximal CRC, and the importance of detection of serrated polyps and their role in colon carcinogenesis.

A key principle of the 2006 guideline was risk stratification of patients on the basis of findings at the baseline colonoscopy. The surveillance schema identified 2 major risk groups on the basis of likelihood of developing advanced neoplasia during surveillance:

  • Low-risk adenoma (LRA), defined as 1-2 tubular adenomas measuring < 10 mm

  • High-risk adenoma (HRA), defined as adenoma with villous histology, high-grade dysplasia (HGD), size ≥ 10 mm, or 3 or more adenomas.

New surveillance intervals. The key change in the 2012 guideline is the recommendation that surveillance intervals should be based on results not only from the patient's most recent colonoscopy, but also from a previous colonoscopy that identified neoplasia. Accordingly, patients who had LRA findings at baseline colonoscopy, and then had no subsequent adenomas detected at first surveillance examination at 5 years, should subsequently be returned to the average-risk screening population and undergo the next surveillance examination at 10 years. However, patients who had HRA findings at baseline colonoscopy and then had no subsequent adenomas detected at first surveillance examination should continue colonoscopy surveillance at 5-year intervals.

Serrated polyps. The second major change to the 2012 guideline addresses the importance of serrated polyps. Some 20%-30% of CRCs arise through a molecular pathway characterized by hypermethylation of genes, known as CpG island methylator phenotype (CIMP). The precursors of this form of CRC are believed to be serrated polyps. The importance of detection and removal of serrated adenomas has received extensive emphasis, given that up to 50% are microsatellite unstable and these CIMP-positive tumors are overrepresented in interval cancers, particularly in the proximal colon. Tumors in this pathway have a high frequency of BRAF mutation and inactivation of multiple tumor suppressor genes. This pathway is predominantly associated with right-sided and poorly differentiated CRC. Furthermore, serrated lesion-related cancers may evidence inactivation of k-ras and a silencing of the DNA repair gene, MGMT. This alteration is particularly associated with distal CRC.

The guideline recommends that patients with a small sessile serrated polyp (< 10 mm) with no dysplasia should have a repeat colonoscopy in 5 years. Patients with a sessile serrated polyp ≥ 10 mm, a sessile serrated polyp with dysplasia (any size), or a traditional serrated adenoma (any size) should undergo repeat colonoscopy in 3 years. Serrated polyposis syndrome should be followed at 1 year, although subsequent examinations that identify a decreasing polyp prevalence can be followed by expanded intervals.

Practical Issues for Clinicians

The updated guideline also addressed several practical questions that arise in everyday practice.

When should surveillance stop? Surveillance and screening should both be discontinued when the risk may outweigh the benefits of screening. The US Preventive Services Task Force (USPSTF) determined that screening should not be continued after age 85 years, because risk could exceed potential benefit. The MSTF did not set an absolute age limit but rather recommended that the decision to continue surveillance should be individualized on the basis of an assessment of benefit, risk, and comorbid conditions. This would be particularly important if the patient never had an index colonoscopy screening.

When should colonoscopy be repeated if there is a poor bowel preparation at baseline colonoscopy? It is well recognized that inadequate-quality bowel preparation can obscure visualization of the colon, causing the endoscopist to miss lesions at the baseline colonoscopy. Current colonoscopy quality indicators for colonoscopy call for monitoring the adequacy of bowel preparation, with the goal of providing visualization for detection of lesions > 5 mm. The guideline reiterates that the evidence is substantial that splitting the dose of bowel preparation results in better-quality preparation, and this practice is strongly recommended. If the bowel preparation is poor, the MSTF recommends that, in most cases, the examination should be repeated within 1 year. If the preparation is fair but adequate to detect polyps > 5 mm and if small LRAs are found, the recommended interval for repeat would be 5 years.

Positive fecal occult blood test or fecal immunochemical test result before scheduled surveillance. The routine use of interval fecal testing in patients undergoing colonoscopy screening/surveillance is not recommended. A decision to perform an early colonoscopy as a result of a positive fecal test result could depend on careful review of the adequacy of the baseline examination. No data at present show an increased rate of cancer or HRAs to support the practice of a routine early examination in these patients. Colonoscopy could be recommended if the colonoscopy was done by a provider with low rates of adenoma detection, suggesting that the examination may have been of lower quality.

Development of new symptoms during the surveillance interval. New symptoms might include minor rectal bleeding, diarrhea, or constipation. The likelihood of finding significant pathology after a previous complete, quality colonoscopy is uncertain but is probably low. The consensus of the MSTF was that there was insufficient evidence to make a specific recommendation, and the indications for repeating the colonoscopy should be individualized on the basis of clinical suspicion.

Viewpoint

It is clear from database evaluations that compliance with colonoscopy screening/surveillance guidelines is suboptimal and reflects both overuse and underuse.[1] Colonoscopy will be subject to increased scrutiny by insurance providers. Compliance with the guidelines is one factor used in defining "quality colonoscopist" and is likely to play a role in reimbursements to low-quality performers in the near future. Accordingly, clinicians should be fully aware of these new recommendations. Although the surveillance intervals after resection of serrated lesions were based on low-quality evidence, the MSTF expects to make modifications to the guidelines, as appropriate, when new data are reported.

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