Headlines are meant to grab your attention. So if you read yesterday that “colonoscopy does not reduce risk of death from colon cancer” it may have sent you into shock. Have we not been conditioned to believe that a colonoscopy is a rite of passage for the middle-aged?
The media headlines were based on results published in the New England Journal of Medicine from a first-of-its-kind large randomized trial. The study suggests that the benefits of colonoscopies for cancer screening in low-risk, asymptomatic people are overestimated. The 10-year study marks the first time colonoscopies have been compared head-to-head with non-cancer screening in a randomized trial.
The study may make people question whether to have the procedure. More troubling, the quotes people hear about the study in the news, on social media, and elsewhere can make them question whether they should be shown at all. However, while colonoscopy may not be the gold standard it has been shown to be, one or more colon cancer screening tools are essential for cancer detection and lower mortality rates.
Unpacking the study
A 2014 comprehensive literature review revealed that “there is no available evidence from RCTs to support the effectiveness of colonoscopy as a colorectal cancer screening test.” Thus, using an RCT methodology, the recently released landmark study sought to test the effect of colonoscopy screening on the risks of both colon cancer and related deaths. Findings over a 10-year period showed that colonoscopies for colon cancer screening had no statistically significant effect on the risk of cancer deaths.
However, in the trial, the 10-year risk of colon cancer was 18% lower among participants who were told to have a screening colonoscopy than among those who were not screened. Also, only 42% of patients randomized to colonoscopy completed the test. Among patients who actually had a colonoscopy, there was a 31% reduction in colon cancer and a 50% reduction in mortality.
What the study doesn’t say
Colorectal cancer is the third leading cause of cancer-related death in men and women in the US. It is predicted to cause more than 52,000 deaths this year. Colon cancer screening is a vital tool in reducing the incidence of cancer deaths. And, this doesn’t just apply to people who are at risk. Low-risk, asymptomatic individuals benefit from screening.
In a 2021 study published in Lancet Oncology, researchers found that since 2000 the incidence and mortality of colon cancer has declined more in European countries with long-standing programs of stool screening, sigmoidoscopy, or colonoscopy than in countries with more recently implemented programs. or no large-scale programs at all.
In addition, in the US and Europe, death rates from colon cancer are in long-term decline. A variety of screening tools used in the US and Europe appear to have played an important role in reducing colorectal cancer death rates.
There has always been confusion about colon cancer screening tools, in part because there are so many options. Some, including flexible sigmoidoscopy and fecal immunochemical testing (FIT), have more evidence to support RCT than others. Flexible sigmoidoscopy is a procedure in which a trained doctor uses a flexible, narrow tube with a light and tiny camera on one end to look inside a person’s rectum and lower colon. A sigmoidoscopy is less invasive than a colonoscopy because it only examines the lower part of the colon, while a colonoscopy examines the entire colon. A sigmoidoscopy is generally recommended once every five years, while a colonoscopy is recommended once every 10 years. Both sigmoidoscopy and colonoscopy can detect and remove polyps.
The FIT test is the least invasive test for colon cancer. It checks for occult blood in the stool, which can be an early sign of cancer. This test only detects blood from the lower intestines. A newer version of the FIT test also detects altered DNA in stool. Depending on the type of FIT test, it is recommended once every one to three years.
Long before the RCT of colonoscopies was published, FIT tests or flexible sigmoidoscopy were first-line colorectal cancer screening tools for low-risk, asymptomatic adults aged 50 to 74 years in many countries, including France , the Netherlands, Norway. Sweden, Denmark, Italy, Spain, United Kingdom, Israel and South Korea.
Testing guidelines disseminated in the UK and the European Union consistently favor the introduction of preventive tests into routine healthcare only after their effectiveness has been demonstrated in randomized trials. As a result, only sigmoidoscopy and guaiac-based FOBT (or the modern version, FIT) are currently recommended for routine use across Europe.
Regarding the use of colonoscopy as a screening method, the only countries outside the US that advise it are Switzerland, Germany and Austria. Interestingly, cancer death rates in Austria and Germany have fallen even faster than other European countries with alternative screening programs. Whether this has anything to do with the more extensive use of colonoscopy has not been investigated.
Closer to home, the Canadian Task Force on Preventive Health Care lists two preferred methods of colon cancer screening for low-risk, asymptomatic adults aged 50 to 74 years:
- Fecal occult blood test (FOBT or FIT), every two years.
- Flexible sigmoidoscopy, every 10 years
On the other hand, the US Preventive Services Task Force (USPSTF) recommends a series of colorectal cancer screening methods for low-risk, asymptomatic adults aged 50 to 74 years, without ranking them according to the strength of the evidence. their. Essentially, the USPSTF guidelines provide equally strong recommendations for all five tests:
- High sensitivity guaiac FOBT or FIT every year. DNA-FIT every 1 to 3 years.
- CT colonography every 5 years.
- Flexible sigmoidoscopy every 5 years.
- Flexible sigmoidoscopy every 10 years plus annual FIT.
- Screening colonoscopy every 10 years.
The USPSTF states that “clinicians and patients can consider a variety of factors to decide which test may be best for each individual.” In fact, for a large and growing segment of the population once-a-decade colonoscopies have replaced the use of alternative tests.
However, more than a quarter of US adults between the ages of 50 and 74 have not been screened for colon cancer. There is a danger that media headlines knocking colonoscopy off its pedestal may misinform Americans about the need to get screened for colon cancer. In fact, they could prevent Americans from being audited not at all for colon cancer.
Perhaps study results like these should come with a disclaimer. Clinicians can and should discuss the benefits of colonoscopy screening over other methods. But screening for colon cancer is essential, either in the form of a colonoscopy or a less invasive tool.