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  • A new study on colonoscopies found that those who received the screening had a 31% lower chance of being diagnosed with colorectal cancer.
  • All Americans are advised to start getting colonoscopies at age 45.
  • The researchers say that the effectiveness of colonoscopies is lower than the estimates from past studies.

Colonoscopies may not be as effective at preventing and reducing the risk of colorectal cancer as we once believed, according to new research.

The study published this week in The New England Journal of Medicine on Monday found that colonoscopies reduced people’s risk of developing cancer, but it was far less than what had previously been observed in other studies.

After adjustments, researchers estimate the screenings are 31% effective at preventing cancer and they can lower their risk of dying from it by about 50%.

Though colonoscopies — a procedure that uses a camera to scope the colon and identify abnormal growths — proved helpful in detecting and preventing cancer, the researchers say that their effectiveness is lower than the estimates from past studies that have informed clinical guidance.

Still, colonoscopies are the best way to detect colon cancer and remove malignancies early.

All Americans are advised to get a colonoscopy starting at age 45 and receive routine screenings every 10 years.

“Colorectal cancer screening, in this case through colonoscopy, decreases colorectal cancer incidence and mortality. This has not changed and thus the message stands,” says Dr. Xavier Llor, MD, co-director of the Smilow Cancer Genetics and Prevention Program and professor of medicine at Yale School of Medicine.

The researchers monitored the health of 84,585 patients in Norway and Sweden over the course of 10 years.

Of the participants, 28,220 were invited to receive a colonoscopy, yet only 11,843 — or 42% — went through with the procedure.

During the 10-year follow up period, 0.98% of patients who were invited to get a colonoscopy were diagnosed with colorectal cancer and 1.2% of patients from the group that was not invited to get screening were diagnosed with colorectal cancer, indicating that the screenings lowered the risk of cancer by about 18%.

The researchers then adjusted the analysis to estimate how effective the screenings would be if everyone who was invited to get a colonoscopy underwent the procedure.

They found that those who received the screening had a 31% lower chance of being diagnosed with colorectal cancer and a 50% lower risk of dying from it.

Even though a 31% lower risk is a significant risk reduction, the researchers say the findings indicate that colonoscopies may be less effective at reducing the risk of cancer than what past estimates have found.

Other studies have found that colonoscopies can reduce the risk of death by up to 68%.

Dr. Uri Ladabaum, MD, MS, a professor of medicine and director of the Gastrointestinal Cancer Prevention Program at Stanford University School of Medicine, says it’s important to recognize that screening participation rates heavily influenced the findings.

Despite the fact that routine colonoscopies save lives, many Americans don’t get them.

“These results should not cast doubt on the effectiveness of colorectal cancer (CRC) screening, or be misinterpreted as evidence that colonoscopy is a poor CRC screening test,” Ladabaum said.

Dr. Anton Bilchik, PhD, a surgical oncologist and division chair of general surgery at Providence Saint John’s Health Center and chief of medicine at Saint John’s Cancer Institute, says that colonoscopies remain the most accurate method to detect colon polyps and reduce the risk of developing colon cancer.

“The findings should not influence standard recent recommendations to start colon cancer screening at age 45 particularly because of the rapid increase of young people being diagnosed with colon cancer,” Bilchik said.

That said, less-invasive alternatives, such as stool-based testing, should be considered in low-risk patients, Bilchik added.

More research is needed to better understand the effectiveness of colonoscopes and whether other types of screening methods may be more useful for certain patients.

“The results of ongoing randomized trials comparing home stool testing to colonoscopy will be pivotal in changing practice patterns and potentially reducing the number of colonoscopies performed,” Bilchik said.

For now, however, colonoscopies continue to be the most effective way to detect cancer and intervene early.

“The message continues to be the same: colorectal cancer screening saves lives,” says Llor.

According to new research, colonoscopies may not be as effective at detecting cancer as medical professionals once believed, however, they still remain the most accurate way to identify colon cancer. The effectiveness also largely depends on participation rates — many people who are advised to do routine screenings do not get colonoscopies.