Colonoscopy is one of those important, routine medical procedures that most people would rather avoid. But experts say the test is a highly effective tool for both preventing colorectal cancer and diagnosing it at an early stage. Colonoscopy is also helpful in diagnosing and treating a variety of gastrointestinal (GI) disorders.
The American Cancer Society recommends that people with an average risk for colorectal cancer start regular screening for that cancer at age 45. There are several choices for colorectal cancer screening; colonoscopy is one of those options and has the advantage of being a one-step test, where precancerous polyps can be identified and removed if they are there at the same time.
For those in good health who have a colonoscopy—a procedure that enables a physician (usually a gastroenterologist) to directly image and examine the entire colon—it does not need to be repeated for ten years.
Those looking for an excuse to put off a colonoscopy might now point to a large study conducted in Europe and published in September 2022 in the New England Journal of Medicine (NEJM) that appeared to question the benefits of colonoscopies.
But many experts caution that the results of the NordICC study are being misinterpreted. They say colonoscopies remain “the gold standard” to detect and prevent colon cancer, and that this study should not cause you to change your behavior, no matter how much patients might wish otherwise.
“People should continue to rely on high-quality colonoscopy for polyp detection and removal, which will lead to prevention in most cases of colorectal cancer,” says David Greenwald, MD, Director of Clinical Gastroenterology and Endoscopy at The Mount Sinai Hospital.
David Greenwald, MD
In this Q&A, Dr. Greenwald, Immediate Past-President of the American College of Gastroenterology, and Co-Chair of New York’s Citywide Colorectal Cancer Control Coalition (C5), discusses the recent study and why the value of colonoscopies remains unchanged.
He adds, “The bottom line: This study, along with prior studies, shows that colonoscopy decreases your chances of getting and dying from colorectal cancer. Getting sick and dying from colorectal cancer—especially due to delayed screening—is real. Screening with colonoscopy saves lives.”
Why is a colonoscopy important?
Colonoscopy is effective in the diagnosis and/or evaluation of various GI disorders, such as colon polyps, colon cancer, diverticulosis, inflammatory bowel disease, bleeding, change in bowel habits, abdominal pain, obstruction and abnormal X-rays or CT scans. It is also used for therapy, such as the removal of polyps or control of bleeding. A colonoscopy is also used for screening for colon cancer. A key advantage of this technique is that it allows both identification of abnormal findings and also therapy or removal of these lesions during the same examination. This procedure is particularly helpful for identification and removal of precancerous polyps.
Does this recent study change how we view colonoscopies and how doctors in the United States will recommend colonoscopy screening?
No. The results of this study must be understood in context, and the accompanying editorial in the same issue of the NEJM spelled out significant details about the strengths and limitations of this study. The bottom line is that colonoscopy is still the gold standard to detect and prevent colorectal cancer, especially for high-risk individuals. Most importantly, in the section of the study that analyzed people who actually had a colonoscopy, the risk of developing colorectal cancer decreased by 31 percent and the risk of dying from colorectal cancer decreased by 50 percent, which is huge.
What is one of the most significant issues with this study?
One drawback of the study is that participants were randomly invited to have a colonoscopy, and many people who should have gotten a colonoscopy chose not to. In fact, less than half (42 percent) of those invited to have a colonoscopy actually had one. This remains an issue in the United States as well. Screening for colorectal cancer remains an enormous public health goal. Colorectal cancer is the second leading cause of cancer death, but fully one-third of the eligible U.S. population remains unscreened.
Are there other issues with the study?
The benefits of colonoscopies take time to be realized. Colon polyps typically take many years (ten or more in most cases) to advance from small polyps to large polyps to cancer, and so the benefits of taking out small polyps or even large precancerous polyps is not seen as leading to a reduction in colorectal cancer for many years, maybe even decades. Other studies that have looked at the effect of removing polyps have shown greater reductions in colorectal cancer incidence and mortality when they looked at outcomes over a longer period of time than was reported in the NordICC study. The NordICC study, short for Northern-European Initiative on Colon Cancer, included more 84,000 men and women ages 55 to 64 from Poland, Norway and Sweden, and covered a period of 10 years, which included a period before these countries began widespread screenings.
Should people still rely on their routine colonoscopy screenings to prevent colorectal cancer?
Yes. People should rely on high-quality colonoscopy for polyp detection and removal, which in most situations will lead to prevention of colorectal cancer. The National Polyp Study demonstrated a substantial decrease in expected colon cancer incidence and mortality related to removing colorectal polyps, and was published in the NEJM years ago. High-quality colonoscopy is key. Nearly 30 percent of the endoscopists who were included in the NordICC trial did not meet a key quality measure. The adenoma detection rate (ADR) measures the percentage of patients who have one or more precancerous polyps detected. The NordICC study did not meet the 25 percent rate that is recommended in the United States; the ADR average in the United States is rising and now approaches approximately 40 percent in many studies.