We thought it was true . . . and now research comes along with evidence.
Colonoscopy reduces death from colorectal cancer.
In a follow-up analysis from the National Polyp Study, people who had adenomas — the risky kind of polyps — removed during the study were much less likely to die from colon or rectal cancer than the general US population. In fact, removing adenomas cut the death rate from colorectal cancer in half.
We knew that colonoscopies find and remove precancerous polyps and reduce the number of new colorectal cancers, but this is the first study to actually link colonoscopy to cutting back death from colorectal cancer.
There was good news in the study for people who didn’t have adenomas too. They had a very low risk of colorectal cancer death. Only one person out of nearly 800 with no adenomas found at the initial exam died of colorectal cancer.
Between 1980 and 1990, the National Polyp Study (NPS) enrolled patients who were having a colonoscopy to rule out colorectal cancer due to symptoms or positive finding on another test. All polyps were removed during the exam. Patients with adenomas had another colonoscopy 1 or 3 years later and again at 6 years. Patients with no polyps or only benign hyperplastic ones had no further testing.
For this long-term follow-up study, Ann Zauber, PhD, and her team used the National Death Index to find those patients in the NPS who died from colorectal cancer. The researchers used the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) registry to figure out how many colorectal cancers could be expected in a group of people with the same age, race, and sex of the NPS participants.
Comparing 2602 NPS adenoma patients to what was expected in the general population there were:
- Overall, 12 deaths in the NPS group compared to an expected 25.4.
- In less than 10 years 4 NPS deaths compared to an expected 9.1.
- For more than 10 years 8 NPS deaths compared to 16.3
In the follow-up study, 2602 patients had adenomas found during their initial colonoscopy, another 773 didn’t.
About a third of the people in the control group did have polyps. But they were the safer hyperplastic type. Only one person in that group of 773 died of colorectal cancer. She died about 8 years after her initial colonoscopy.
Ann Zauber PhD and her team concluded,
These findings support the hypothesis that colonoscopic removal of adenomatous polyps prevents death from colorectal cancer.
Dr. Zauber also wrote,
A demonstrated reduction in mortality with colonoscopic polypectomy is a critical prerequisite for continued recommendations of screening colonoscopy in clinical practice while we wait for the results of randomized, controlled trials of screening colonoscopy.
What This Means for Patients
Advocates can confidently say that colonoscopy saves lives. Not only does it prevent colorectal cancer from ever happening, it cuts deaths in half.
However, deaths were not zero. Patients who have had adenomas removed during a colonoscopy need to remain aware of the symptoms of colorectal cancer and have them evaluated with another colonoscopy if they occur.
It is also important to remember that the National Polyp Study involved high quality colonoscopies. The gastroenterologists who performed them were experts and all cases included in the study reached the top of the colon.