Colorectal cancer is the second leading cause of cancer death worldwide.
Studies show that screening for colorectal cancer reduces the risk of death from the condition. The most commonly used screening tests are fecal testing and colonoscopy, the insertion of a small camera into the digestive tract.
Currently, the U.S. Preventative Services Task Force recommends that people undergo a colonoscopy every 10 years starting at age 45.
However, the procedure has not been adopted in other areas of the world, partially due to a lack of randomized trials attesting to its benefits.
Understanding the possible advantages of a colonoscopy vis-a-vis other screening methods could help improve public health recommendations and colon cancer preventive strategies.
Recently, researchers assessed the effectiveness of colonoscopy invitations in Poland, Norway, Sweden, and the Netherlands in reducing colon cancer-related deaths.
The researchers found that colon cancer risk among those who were screened was lower compared to those who were not screened over a 10-year period but noted the effectiveness of preventing colon cancer was lower than previously thought.
The study was recently published in The New England Journal of Medicine.
For the study, the researchers enrolled 84,585 men and women ages 55 to 64 years old who had not undergone prior colorectal cancer screening.
The participants were randomly assigned in a 1:2 ratio to either receive an invitation for a single colonoscopy or to receive usual care (no invitation and no screening).
Altogether 28,220 people were invited to receive a colonoscopy, of which 11,843, or 42%, underwent screening.
The researchers noted that 15 participants experienced major bleeding after polyp removal. However, no perforations or screening-related deaths occurred within 30 days of colonoscopy.
After 10 years of screening, the researchers recorded 259 diagnoses of colorectal cancer in the invited group compared to 622 cases in the usual-care group.
This translated to a 0.98% risk of colorectal cancer within 10 years in the invited group and a 1.2% risk in the usual care group.
Overall, the researchers noted that a colonoscopy invitation reduced the risk of developing colorectal cancer within 10 years by 18%. They noted, however, that both groups had an almost identical risk of death from colorectal cancer at 10 years.
But not all experts agree with the study findings and suggest the results may have some limitations.
“The conclusion derived in the study that an 18 % reduction in colorectal cancer detection and nearly 0% lives saved due to colorectal cancer is misleading,” Dr. Vanitha Bala, a gastroenterologist at Memorial Hermann Medical Group in Houston, Texas, not involved in the study, told Medical News Today.
“If only the group that underwent screening [11,843 individuals] is considered, then the patient’s chance of colorectal cancer reduces by 31% (18% in the study), and the risk of death is reduced by 50% (0% in the study),” she noted.
When asked about the study’s limitations, Dr. Elena Ivanina, the director of neuro-integrative gastroenterology at Northwell Health, not involved in the study, told MNT:
“The biggest nuance in this study is the difference between ‘invited to perform a colonoscopy’ and actually doing the colonoscopy. Their conclusions describe the results of people who were ‘invited’ to do a colonoscopy, of whom only 42% actually did the colonoscopy. In their adjusted analysis of the people who actually got a colonoscopy, there was a 50% reduction in mortality which is incredibly significant.”
Dr. David A. Greenwald, director of clinical gastroenterology and endoscopy at Mount Sinai Hospital, explained to MNT:
“Another issue with the study is the quality of the colonoscopies performed by about one-third of the physicians that were below what is considered minimum standards in the U.S. There is ample literature that a high-quality colonoscopy is required to be effective at preventing CRC and CRC-related deaths, and that colonoscopy is highly operator dependent.
“There are many benchmarks developed and validated as a result, including adenoma detection rate. The benchmark for adequate adenoma detection is 25 percent. In the U.S., the average adenoma detection rate is 39 percent, while in the current study, nearly one-third of endoscopists were below even that 25 percent benchmark,” he added.
To put this into perspective, Dr. Ivanina said: “Every 1% increase in the ADR is associated with a 3% reduction in future incidence of colorectal cancer and 5% reduction in colorectal cancer-related death.”
Dr. Nancy You, professor of colon and rectal surgery at The University of Texas MD Anderson Cancer Center, not involved in the study, said that while the study reported a 42% screening rate, the same figure has increased from 38% to 63% in the U.S., where screening recommendations have been enforced for longer.
Commenting on the countries involved in the study, she explained to MNT:
“These are countries starting to build infrastructure for population-based screening. There is a learning curve for the public, for physicians, for pathologists, for policymakers, and everyone involved.”
“Unknown variables that impact the ability for colonoscopy to successfully identify cancer include quality of prep, quality of endoscopist, quality of equipment, quality of post-screening surveillance and follow-up after initial scope,” she continued.
“This study adds to prior evidence showing the importance of colonoscopy for colon and rectal cancer screening, treatment, and prevention,” Dr. Heather Yeo, colon and rectal surgeon at Weill Cornell Medicine, not involved in the study, told MNT.
“While we have better screening in the US than in many other countries, nationally could still do more, with most states having less than 50% of those recommended for screening and colonoscopy receiving the treatment,” she noted.
“Many patients are afraid of colonoscopy because of the prep. While a bowel prep is no fun, we know that colonoscopy can not only help diagnose early cancer, by finding precancers that can be removed through the scope it can prevent cancers,” she added.
Dr. Samir Gupta, professor of medicine at the University of California, San Diego, not involved in the study, told MNT:
“The good news here is that we have, for the first time, clear randomized controlled trial evidence that inviting people to do colonoscopy can prevent cancer. The results also indicate that while colonoscopy is a good test, it does not yet have randomized trial data showing that it is clearly superior to other tests.”
“This means that we should continue to make sure that patients understand that the most important thing is to get screened and that they should choose the option that works best for them,” Dr. Gupta added.
“Patients who want the most sensitive and least frequent test may choose colonoscopy, while those who prefer a noninvasive option can choose stool-based testing like FIT or FIT DNA. Available evidence suggests that either option can have significant benefits.”