Why Colon Cancer Screening Is Suddenly Controversial

If you recently turned 45, you’re probably wondering if a colonoscopy is worth the hassle. 

Maybe your friends are talking about their recent procedures or your doctor is reaching out about the needs for colon cancer screening. You may have also read news stories about a study that claimed colonoscopies don’t reduce your risk of colon cancer or death. But a closer look at the study actually reveals colonoscopies are remarkably effective.  

Colonoscopies are the most common screening procedure for colon cancer in the U.S. It’s a procedure that uses a flexible scope to examine your entire colon, and it requires preparation and sedation as well as carries the risks of perforation and bleeding (though these risks are very low).  

Given the invasiveness of the colonoscopy as well as the complexity of performing it, many people want to know if the risks and complications of colonoscopies are worth it and if the procedure is saving lives.  

A recent article in New England Journal of Medicine was designed to answer this question by evaluating the effect of colonoscopy on the risks of colorectal cancer and related death. Unfortunately, the results were widely misrepresented by the press.  

What new research discovered about colonoscopies  

The study included 84,585 European participants between 55 and 64 years old who were observed for 10 years. Researchers randomly assigned 28,220 participants to receive an invitation for a colonoscopy (the intervention group). The rest of the participants received their usual care, which did not include a colonoscopy (the control group). Importantly, only 42% of those who were offered a colonoscopy got one.  

At the 10-year follow-up, the people in the invitation group had an 18% reduced risk of developing colon cancer. These benefits were far less than many experts expected and led to misleading headlines about the effectiveness of colonoscopies.  

However, what many journalists failed to report was that when you looked at patients who actually got a colonoscopy (versus all folks in the intervention group), the effectiveness of the procedure was impressive.  

The study found only 259 participants who received a colonoscopy developed colon cancer as compared to 622 in the control group. These findings translated into a 30% reduction in colon cancer risk and 50% reduction in colon cancer death for those who received a colonoscopy.  

In other words, the risk of colorectal cancer during those 10 years was lower among participants who were invited to undergo screening colonoscopy than among those who weren’t. Moreover, when you look at the 42% of people who decided to receive a colonoscopy, the study found a reduction in both colorectal cancer risk and death.     

The study also emphasized the effectiveness of detecting adenomas (benign polyps that can become cancerous over time) during a colonoscopy. We know from past studies that having an adenoma increases your risk of developing colorectal cancer, so it’s crucial to be able to detect and remove these polyps.     

In this study, adenomas were detected and removed during a colonoscopy in 3,634 participants (30.7% of those who underwent screening). Consider a simple calculation: If you use a rough estimate, you find that among the 3,634 participants with removed adenomas, 908 would have been diagnosed with colon cancer in 20 years if their adenomas had not been removed. Removing these adenomas during the colonoscopies prevented cancer diagnoses and saved lives.  

Why the study caused controversy about colonoscopies  

This recent study has made some waves because it found that colonoscopies reduced colon cancer risk by about 18%, which is notably less than past research that found colonoscopies can reduce risk and death by around 70%.   

One of the reasons this may have been the case is the study had a low percentage of people who actually decided to get a colonoscopy (42%). If you only look at those individuals who received a colonoscopy, you find a roughly 30% reduction in colon cancer risk, as well as a 50% reduction in colon cancer death. Another factor is that screening technology has improved in the 10 years since this study began.   

While these results are lower than past research, this study still confirms getting a colonoscopy reduces your risk of getting or dying from colon cancer, especially when you consider how removing adenomas reduces risk.   

The key takeaway: yes, colonoscopies save lives  

Despite the controversy, this important study actually confirms what we know already: Colonoscopies are saving lives.   

If you are between 45-75 years old and you don’t have a family history of colon cancer or an inflammatory bowel disease, you have multiple screening options, including colonoscopies, stool tests and sigmoidoscopy (which is similar to a colonoscopy but only examines part of the colon with a scope). Talk to your doctor to make an informed decision about which test is most appropriate for you. 

If you do have risk factors for colon cancer — or if you simply want to go with the gold standard screening — then a colonoscopy is the best option for you to get screened for colorectal cancer.    

Dr. Natalia Usoltseva is a clinical assistant professor at UW School of Medicine, the physician lead for best practices in population health for UW Medicine Primary Care and the clinic chief at UW Medicine Primary & Urgent Care at Ballard. She believes in the importance of preventive medicine and strives to provide patients with all the necessary tools for good health. In her spare time, she enjoys hiking, skiing with her husband and children, jogging, and reading modern and classic literature.