A recent European study has proposed colonoscopies are not as effective nor provide the overall benefits as a screening for colon cancer as previously thought. In the United States, colonoscopies are recommended beginning at the age of 45, a recent change from age 50, as the incidence rate of colorectal cancer in younger people has spiked in recent years.
To understand the results, and what they actually mean, context is crucial. Victor Lin, M.D., Ph.D., Mary Bird Perkins Cancer Center; R. Scott Daugherty, M.D., colorectal surgeon, Baton Rouge General Colon and Rectal Associates; and Michael Barker, M.D., gastroenterologist, GI Alliance and Baton Rouge General Crohn’s and Colitis Clinic, say the bottom line remains – colonoscopies are effective at detecting and diagnosing colorectal cancer. They also serve as a preventative measure, allowing for the removal of pre-malignant polyps.
What did the recent European study actually find, and what do those results mean?
Dr. Lin: The NordICC trial was trying to find out whether screening colonoscopies are effective at reducing the incidence of colorectal cancer and associated risk of death. In Europe, routine screening colonoscopies are not recommended as standard care, so participants in the trial were randomized either to be invited to undergo a screening colonoscopy or to continue with routine care. The bottom line of the study per the authors was that their intervention led to no statistically significant difference in the risk of death from colon cancer and only a very small reduction in colon cancer incidence. This has led some to conclude that screening colonoscopies are less effective than previously thought.
Unfortunately, the intervention studied in the trial was not to undergo a screening colonoscopy, but rather to be invited to undergo a screening colonoscopy. Thus, the proper interpretation of the study is that inviting patients to undergo a colonoscopy is no better than not inviting patients to do so. This is a critical distinction as fewer than half (only 42%) of patients invited to undergo the procedure actually had it done.
What factors (sedation, thoroughness) could have led the researchers to finding that colonoscopies may be less effective (lower success rates) at reducing the risk of colorectal cancer?
Dr. Daugherty: When you take a closer look, less than half of the people in the study who were invited to get colonoscopies actually went through with them. This is the type of flaw you run into with randomized trials of cancer screening tests – they can become more of a trial of who accepts the invitation to screen, not the test itself. When you look at the results of those in the study who actually got colonoscopies, the numbers are good – there was a 31% reduction in colon cancer risk and a 50% reduction in risk of dying from it.
Dr. Barker: There were multiple factors in the study that limited the effectiveness of colonoscopy in preventing colorectal cancer. The majority of the participants in the study were from Poland who hold the lowest acceptance rate for colonoscopy of 33%. Another limiting factor of the study was the skill of the endoscopists. Adenoma detection rate (ADR) is a measure of how effective an endoscopist is at detecting pre-malignant lesions during a colonoscopy. In the United States the average endoscopist has a 40% ADR, whereas in the study 30% of the endoscopists did not meet the recommended rate of 25%. Even with the low participation in those invited and low ADR in those who underwent colonoscopy, the decrease in mortality was 50%. This shows that colonoscopy is a very effective tool at preventing colorectal cancer when performed.
Dr. Lin: I would start by pointing out that analysis of the minority of patients that did follow through with a screening colonoscopy actually benefited in terms of reduced colorectal cancer incidence and related death at a rate that matched prior non-randomized studies. However, there is also concern that the detection rate of polyps in the NordICC trial is lower than what is considered to be the baseline. This may be related to less experience doing the procedure, as screening colonoscopies less frequent in Europe. This may also be due to the fact that anesthesia in not as commonly used for these procedures in Europe, and patient discomfort in the absence of anesthesia can result in a less thorough colonoscopy. Finally, there is typically a long lag time between when a polyp first develops and when it becomes cancerous, so it is possible that a higher degree of benefit will be seen at a later time (the study plans to report updated results again in several years).
Why do colonoscopies remain the ‘gold standard’ in the United States?
Dr. Barker: Don’t let the media guide your healthcare decisions. Colonoscopy remains the gold standard of colorectal cancer prevention because it is not only diagnostic, but also therapeutic. Colonoscopy is effective in the U.S. population and can decrease your risk of dying from colorectal cancer. The goal of colorectal cancer screening is to prevent the disease. Colonoscopy can remove polyps before they become colon cancer, which is the ultimate goal.
What other methods of screening for colon cancer may be recommended?
Dr. Daugherty: If you’re 45 or older, it’s important to talk with your doctor about a colon cancer screening. While a colonoscopy is the most traditional and comprehensive test for colorectal cancer, another option is the Cologuard test. This is the only stool DNA test approved by the FDA for colorectal cancer screening.
Dr. Lin: Non-invasive methods of colorectal cancer screening include fecal occult blood testing (FOBT), fecal immunochemical testing (FIT), and stool DNA testing. These involve testing a stool sample for signs of developing cancer. CT colonography (virtual colonoscopy using a CT scanner) is also an option. Finally, flexible sigmoidoscopy is done with a smaller endoscope that looks only at the distal part of the large intestine, but is considered less invasive than a colonoscopy. However, it is important to note that all of these tests are thought to be less sensitive than a colonoscopy and are usually not recommended for patients considered to be at above-average risk for colorectal cancer. Furthermore, if any of these tests returns an abnormal result, the recommendation is generally to proceed with a colonoscopy. If there is an abnormal finding during a colonoscopy, such as a precancerous polyp, it can usually be removed during the procedure. This is not true of any of the other testing modalities. Because of that, I still believe that screening colonoscopies are the best way to screen for colorectal cancer.
For more information on determining the screening that is right for you, please contact your physician.
For a link to free community colorectal cancer screenings, click here.