Adenomatous polyp

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Precursors to the majority of large bowel malignancies.

Found in up to 40% of persons by 60 years of age and 50% by age 70.

Precursor to almost all sporadic colorectal cancers.

There has been an increase in the prevalence of polyps 9 mm or larger in people younger than 50 years.

Removal of adenomas reduces colorectal cancer incidence and mortality.

Adenoma-carcinoma sequence refers to progression of normal colon mucosa to small adenomas than to large adenomas and eventually to advanced histologic changes with villous features, dysplasia and then to cancer.

Estimated seven to ten years required for and adenoma to progress to a malignancy.

90% of adenomas do not lead to cancer, but it is presently not possible to identify those that will progress.

Colon adenomatous polyp identification by colonoscopy may be less protective in women than in men.

In an administrative study women were 41% more likely than men to develop colorectal cancer despite undergoing colonoscopy (Bressler).

Colonoscopy associated with decreased risk of a subsequent colorectal cancer by two thirds for lesions in the proximal colon and suggests that the lower prevalence of adenomas in women may translate into possible less efficacy of colonoscopy (Baxter).

In a meta-analysis of 924,932 adults the relative risk in men vs. women is 1.83 (Nguyen SP).

May indicate an increased risk of metachronous adenomas and colorectal cancer in the patient and their first degree relatives.

Usually asymptomatic and found by endoscopy and radiographic imaging techniques.

At least 25% of men and 15% of women who have colonoscopic screening have one or more lesions.

One fourth of 4.4 million annual colonoscopies are for polyp surveillance.

U.S. Multi-Society Task Force recommends follow-up colonoscopy after removal of an advanced adenoma (Levin B).

Larger size and more advanced histological features are independent risk factors for invasive cancer and such lesions are referred to as advanced adenomas for polyps greater than 1 cm or larger in diameter or has villous, tubulovillous, or high grade dysplastic findings on histologic evaluation.

Calcium supplementation causes a slight but significant reduction in adenoma recurrence.

Fiber supplementation increases the recurrence rate of adenomatous polyps.

Patients with colonic adenomas found at colonoscopy should undergo surveillance colonoscopy 3 years later because of the risk of metachronous neoplasms.

Risk of development of a metachronous adenoma after the removal of an adenoma is about 5-10%.

The presence of three of more adenomas or one or more advanced adenomas increases the risk of a metachronous adenoma by 2-3 fold.

A single diminutive adenoma not associated with a greater risk of developing colorectal cancer than those without adenomas.

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Those at risk for a subsequent neoplastic lesion are those with three or more adenomas, have high grade dysplasia, villous features or an adenoma of ≥1 cm in size and should have 3-year follow up colonoscopy, while people with 1-2 small (<1 cm) lesions, tubular adenoma features and no high grade dysplasia can have a follow up in 5-10 years.

Sessile serrated polyps (SSPs), are difficult to detect and have potential to become malignant colorectal tumors, appear to be caused by a single oncogenic mutation.

Serrated polyps represent a precursor lesion of colorectal cancer and contribute to approximately 1/3 of colorectal cancer cases through an alternative pathway.

The serrated pathway plays an important role in development of interval cancers, which occur despite appropriately timed endoscopic surveillance.

The serrated pathway is characterized by CpG island methylation phenotype, BRAF mutation, and often microsatellite instability.

V600E mutation in BRAF (V-Raf Murine Sarcoma Viral Oncogene Homolog B) is the sole cancer-causing mutation in SSPs.

Approximately one-third of sporadic colorectal cancers, which account for about 95% of all colorectal malignancies, are thought to arise from premalignant serrated lesions, including SSPs, hyperplastic polyps, and traditional serrated adenomas.

Although SSPs and traditional serrated adenomas both have significant potential for malignant transformation.

The National Polyp Study revealed that removal of adenomas via colonoscopy resulted in a decrease in cancer incidence from 76 to 90%.

National Polyp Study demonstrated colorectal cancer was prevented by colonoscopic polypectomy in a study of mortality from colorectal cancer.

In a study of 2602 patients with adenomas removed during the participation of the study after a median of 15.8 years, 12 died from colorectal cancer with expected estimated 25.4 deaths, suggesting a 53% reduction in mortality(National Polyp Study).

In the above study mortality from colorectal cancer was similar among patients with adenomas and those with non-adenomatous polyps during the first years after polypectomy (Zauber AG et al).

The National Polyp Study included 1418 patients with one or more adenomas and who underwent periodic colonoscopy for an average follow-up of 5.9 years.

Age adjusted prevalence of adenomas and colorectal cancer is higher among men than women.

One study showed that every one percentage point increase in an adenoma detection rate is associated with a 3% reduction in the future incidence of colorectal cancer and a 5% reduction in colorectal cancer death rate.

The adenoma detection rate among endoscopists is recommended at 25%.

Finding of one or more advanced adenomas on sigmoidoscopy associated with rate of metachronous proximal colon cancer (above the sigmoidoscope) about 5 times higher than that in the general population.

Risk of advanced cancer at follow-up colonoscopy depends on the number, size, and histology of baseline adenomas.

Guidelines for follow-up colonoscopy for a low-risk group is no surveillance or surveillance at 5-10 year intervals.

An intermediate risk or higher-risk group for which surveillance every 3 years is recommended.

A high-risk group an addition clearing by colonoscopy is recommended within 3 years.

The risk of advanced neoplasia at follow-up colonoscopy depends on the size, number, and histology of baseline adenomas, as well as the quality of the baseline examination.

Criteria for three year surveillance is for 3 to 10 adenomas or any adenomas greater than 10 mm with villous architecture or high-grade dysplasia.

Three-year surveillance is not stopped except for older age.

Approximately 25% of colonoscopies are for adenoma surveillance.

Colonoscopy surveillance benefits most patients with intermediate risk adenomas.

US Preventative Services Task Force has concluded that aspirin reduces the risk of colorectal cancer by 40% and it should be prescribed routinely to patients with advanced colorectal polyps.

US Preventative Services Task Force

1. For patients with normal, high-quality colonoscopy, repeat colorectal cancer (CRC) screening in 10 years.

2. For patients with 1-2 tubular adenomas <10 mm in size completely removed at a high-quality examination, repeat colonoscopy in 7-10 years.

3. For patients with 3-4 tubular adenomas <10 mm in size completely removed at a high-quality examination, repeat colonoscopy in 3-5 years.

4. For patients with 5-10 tubular adenomas <10 mm in size completely removed at a high-quality examination, repeat colonoscopy in 3 years.

5. For patients with 1 or more adenomas ≥10 mm in size completely removed at high-quality examination, repeat colonoscopy in 3 years.

6. For patients with adenoma containing villous histology completely removed at high-quality examination, repeat colonoscopy in 3 years.

7. For patients with adenoma containing high-grade dysplasia completely removed at high-quality examination, repeat colonoscopy in 3 years.

8. For patients with >10 adenomas completely removed at high-quality examination, repeat colonoscopy in 1 year.

9. For patients with ≤ 20 hyperplastic polyps (HPs) <10 mm in size in the rectum or sigmoid colon removed at a high-quality examination, repeat CRC screening in 10 years.

10. For patients with ≤ 20 HPs <10 mm in size proximal to the sigmoid colon removed at a high-quality examination, repeat colonoscopy in 10 years.

11. For patients with 1-2 sessile serrated polyps (SSPs) <10 mm in size completely removed at high-quality examination, repeat colonoscopy in 5-10 years.

12. For patients with traditional serrated adenomas (TSAs) completely removed at a high-quality examination, repeat colonoscopy in 3 years.

13. For patients with 3-4 SSPs <10 mm at high-quality examination, repeat colonoscopy in 3-5 years.

14. For patients with any combination of 5-10 SSPs <10 mm at high-quality examination, repeat colonoscopy in 3 years.

15. For patients with SSP ≥10 mm at a high-quality examination, repeat colonoscopy in 3 years.

16. For patients with HP ≥10 mm, repeat colonoscopy in 3-5 years. A 3-year follow-up interval is favored if concern about pathologist consistency in distinguishing SSPs from HPs, quality of bowel preparation, or complete polyp excision, whereas a 5-year interval is favored if low concerns for consistency in distinguishing between SSP and HP by the pathologist, adequate bowel preparation, and confident complete polyp excision.

17. For patients with SSP containing dysplasia at a high-quality examination, repeat colonoscopy in 3 years.

18. For patients with history of baseline adenoma removal and one subsequent colonoscopy, recommendations for subsequent surveillance should take into account findings at baseline and first surveillance.

19. For patients with piecemeal resection of adenoma or SSP >20 mm, repeat colonoscopy in 6 months.