How often should you have a colonoscopy if polyps are found

Post-polypectomy and post-cancer resection surveillance are the most common indications for performing colonoscopy.1 A summary of the new guidelines on colonoscopy surveillance for patients with these indications appears in this issue of American Family Physician.2 Developed jointly by the U.S. Multi-Society Task Force on Colorectal Cancer and the American Cancer Society, and endorsed by the major U.S. gastrointestinal organizations, these new guidelines were made to clarify inconsistencies in previous guidelines and to provide a stronger consensus on when to refer patients for repeat colonoscopy. Studies have shown that a large number of patients have been referred for repeat colonoscopy sooner than appropriate, which raises the concern that more resources are potentially being drained from screening colonoscopies.3,4 These guidelines are intended to help correct the disparity between patients who have too many colonoscopies and those who have too few or none at all.

What do the new guidelines recommend for post-polypectomy surveillance? Essentially, they place patients into one of three groups: no-risk, low-risk, or high-risk for developing colorectal neoplasia, based on the results of their initial screening colonoscopy. Patients in the no-risk group may have small rectal hyperplastic polyps and should have a repeat colonoscopy in 10 years. Patients in the low-risk group have one or two small adenomas that are smaller than 1 cm and have no or only low-grade dysplasia; they should have a repeat colonoscopy in five to 10 years. Patients in the high-risk group have three or more adenomas or polyps 1 cm or larger, or high-grade dysplasia, and should have a repeat colonoscopy in three years.

Several other complex issues are also addressed in the guidelines, such as patients with hereditary nonpolyposis colorectal cancer, patients with more than 10 adenomas, those who have had a piecemeal polypectomy, and the quality of the colonoscopy.

What do the new guidelines recommend for surveillance after colorectal cancer resection? The initial endoscopic evaluation should be complete and thorough. If an obstructing lesion prevents a high-quality clearing colonoscopy, one should be performed three to six months after resection. Subsequent colonoscopies should occur one, three, and five years from the resection, unless findings warrant an earlier examination. In patients with rectal cancer, local endoscopic examinations every three to six months for two to three years after the resection are important to evaluate for metachro-nous disease (i.e., neoplasia that develops after the initial lesion).

It is important to keep in mind that colonoscopy is not perfect. In rare circumstances, patients undergoing surveillance may develop high-risk lesions or cancer much sooner than would be expected after colonoscopy.5,6 Current evidence suggests that this may be the result of incomplete polyp removal, missed lesions, and rapidly evolving cancers. The gastroenterolo-gist must assess the quality of the baseline colonoscopy (i.e., quality of the preparation, completeness of polyp removal, and withdrawal time) and make recommendations to the patient and primary care physician. Physicians should use these new guidelines to determine when to repeat colonoscopy. No studies have shown a benefit to repeat colonoscopy sooner than guideline recommendations. The fact remains that the first screening colonoscopy is the most effective in reducing the incidence of colorectal cancer in patients with adenomatous polyps.7

These guidelines likely will continue to evolve for two reasons. First, new follow-up data on patients who have adenomas and cancer continue to be presented. Studies that were released after these guidelines continue to support the current risk-stratification classification8; however, as our understanding of tumor biology improves, guidelines will certainly change. Second, as more data are presented on newer screening and surveillance methods, especially computed tomography colonography, guidelines will need to address when and how to appropriately follow these patients, based on findings.

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Diseases & Conditions

February 2, 2022

Follow-up exams at the right time are essential to prevent cancer from developing.

Colorectal cancer is one of the most preventable forms of cancer—if you are screened for hidden warning signs while you are still healthy. Screening finds precancerous growths on the colon wall, called polyps, which the doctor can then remove.

"They are not cancer, and most of them have not started to change into cancer," says Dr. John Saltzman, associate professor at Harvard Medical School and director of endoscopy at Brigham and Women's Hospital in Boston. "If you get them at the precancerous phase, they don't have a chance to grow and turn into cancer."

But you will need to come back for follow-up testing to see if more polyps turn up in the future. Here is what to expect.

What are polyps?

A colonoscope, the flexible device used to inspect the colon, can grab and snip off polyps if they are relatively small. The timing of follow-up depends on what kind of polyps the doctor finds, how many, and how big they are.

Hyperplastic polyps: These polyps are not precancerous. Doctors generally remove them anyway, just to be safe.

Adenomas: Many colon polyps are the precancerous type, called adenomas. It can take seven to 10 or more years for an adenoma to evolve into cancer—if it ever does. Overall, only 5% of adenomas progress to cancer, but your individual risk is hard to predict. Doctors remove all the adenomas they find.

Sessile serrated polyps: Once thought harmless, this type of adenoma is now known to be risky. These are also removed.

When to return for follow-up

After polyps are removed, you will need to return for an additional colonoscopy. There is a 25% to 30% chance that a repeat colonoscopy will find additional polyps. How soon you need to return for follow-up depends largely on the size of the polyps found in the first exam.

If the colonoscopy finds one or two small polyps (5 mm in diameter or smaller), you are considered at relatively low risk. Most people will not have to return for a follow-up colonoscopy for at least five years, and possibly longer.

If the polyps are larger (10 mm or larger), more numerous, or abnormal in appearance under a microscope, you may have to return in three years or sooner.

If the exam finds no polyps, "your cancer risk is essentially the average for the population, and you can wait 10 years for the next screening," Dr. Saltzman says.

How a colon polyp progresses to cancer

Get the best exam you can

Whenever you have a colonoscopy, you should have the highest quality exam possible so the doctor can find all the polyps. During the colon-cleansing "prep" before the colonoscopy, follow the instructions to the letter. Eating a low-fiber diet for four to five days may improve the quality of the prep, Dr. Saltzman says. That's because fiber gets stuck in the nooks and crannies of the colon wall and can block the doctor's view. For colonoscopy to prevent cancer, the doctor must find and remove as many precancerous growths as possible.

Reducing your risk

After polyp removal, certain steps may lower your risk of colon cancer:

Eat less meat: Eat a healthy diet, with minimal red meat—especially processed or cured meats. Studies suggest that people with meat-rich diets tend to have higher rates of colon cancer.

Aspirin: Some research suggests that taking aspirin may reduce overall colon cancer risk, but the evidence is not definite. If you need to take aspirin for your heart, then it may offer some protection for the colon.

Calcium: Research has also linked a calcium-rich diet to lower colon cancer risk, but this, too, is uncertain. If you are already eating a healthy calcium rich diet to preserve bone health, you might get an extra "bump" of cancer prevention.

Image: SciePro/Getty Images

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As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles.

No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

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