Colonoscopy can be an arduous form of screening, requiring meticulous preparation. Fortunately, for most people it does not need to be performed very often—every 10 years if you’re at average risk for colorectal cancer and have a clean colonoscopy.
But you’ll be advised to come back sooner if you’ve had precancerous polyps removed (polypectomy) during your colonoscopy. The timing for your subsequent screenings will depend on the number, size, and types of polyps found; their location in your colon; and other risk factors for developing colorectal cancer.
The most recent guidelines for colonoscopy screening take into account research confirming the highly protective effect of colonoscopy in reducing colorectal cancer death. The clinical evidence has only gotten stronger in recent years, which means that adhering to a colonoscopy schedule appropriate for your risk is definitely worth the trouble.
Polyps are not uncommon
It seems only logical that removing potentially cancerous tissue early would reduce the likelihood of cancer and cancer-related death, a theory borne out by long-term research.
Researchers who followed 2,602 screened patients with adenomas over a period of about 15 years found that colonoscopy with polypectomy reduced the rate of colon cancer–related deaths in their study population by more than half.
In fact, the study, published in The New England Journal of Medicine in 2012, found that in the first 10 years after colonoscopy, participants who had polyps removed had about the same risk for developing cancer as patients who had no polyps to begin with.
The United States Preventive Services Task Force (USPSTF) and other expert medical organizations recommend most people start getting screened for colon cancer at age 50; those with a family history of colorectal cancer or polyps or a personal history of inflammatory bowel disease or certain inherited conditions should get screened sooner.
The surveillance interval—that is, how much time should elapse before you are rescreened—hinges on a number of variables that researchers have developed a better understanding of in the past several years. A key consideration is the number and types of polyps detected during your colonoscopy.
Up to 50 percent of adults are found to have one or more polyps, but not all of these growths are cause for concern. A type of polyp known as hyperplastic, for example, has virtually no chance of becoming malignant.
However, because it’s not always possible to distinguish a hyperplastic polyp from a precancerous type, a biopsy usually follows removal. Patients who have small, hyperplastic polyps in their rectum or sigmoid colon can usually wait the full 10 years until their next colonoscopy.
Another type of colon polyp is an adenoma, which does carry a cancer risk. But adenomatous polyps are slow growing and usually take years to become cancer. Generally, the larger the adenoma, the more likely it is to become malignant.
Thus, the presence of one or two tubular adenomas less than 10 mm in size is considered low risk. (Adenomas have several different growth patterns, and “tubular” is less likely to be cancerous.) If you have a low-risk adenoma, you can safely wait between five and 10 years until your next colonoscopy.
The questionable types
Your endoscopist is likely to recommend another colonoscopy in three years if you have between three and 10 tubular adenomas, or if one of those adenomas is larger than 10 mm. If you have more than 10 tubular adenomas, you should undergo another colonoscopy in less than three years.
Shorter surveillance intervals are also recommended for people who have adenomas with a villous growth pattern, which are more likely to quickly develop into cancer, and for people with adenomas that are found to have high-grade cell abnormalities (dysplasia). People with either of these two types should have their next colonoscopy in three years.
Researchers are still trying to figure out the best way to manage patients who have serrated polyps, which are flat and often found in the right side of the colon. At this point, serrated polyps are handled like high-risk adenomas if they are larger than 10 mm or contain dysplasia, with a surveillance interval of three years, and like low-risk adenomas if they are less than 10 mm and do not contain dysplasia, with a surveillance interval of five years.
Serrated polyps can be difficult to remove during colonoscopy, and patients may be referred for surgery. However, even the most challenging growths can be removed endoscopically in the hands of a skilled specialist through a process called endoscopic mucosal resection, according to a study published in Gastrointestinal Endoscopy in January 2014.
Patients should have a repeat colonoscopy within one year if there is any question about the thoroughness of resection. The same holds true if bowel preparation was inadequate, which can result in missed adenomas during a screening.
Another factor doctors take into consideration when determining a screening schedule is the state of findings after a patient has undergone a surveillance interval and repeat colonoscopy. For example, if you had a low-risk adenoma detected during your first colonoscopy and no adenomas detected during a subsequent screening, then you can wait 10 years before having the third.
But if you had a high-risk adenoma found during your baseline colonoscopy and no adenomas at your second screening, your doctor should advise you to wait no more than five years before your third colonoscopy.
If you’re not sure why you were given a certain time interval for your next colonoscopy, be sure to ask your gastroenterologist to explain. You can also ask how he or she handles the different types of polyps.
The good news is that, at some point, you can probably stop worrying about having colonoscopies.
The USPSTF recommends most people stop getting colonoscopies after the age of 75 unless prior findings or other health issues suggest it would be beneficial. Colonoscopy is not recommended for people 85 and older.