Doctors may be performing too many repeat colonoscopies on people who've had pre-cancerous polyps removed during an earlier colon cancer screening, a new Norwegian study suggests.
Many of these patients have no greater risk of dying from colon cancer than the general public, the researchers determined.
People who have a single low-risk polyp removed have a much lower risk of colon cancer, compared to both the general public and patients who have multiple polyps or aggressive polyps removed, said lead author Dr. Magnus Loberg, a lecturer in health management and health economics at the University of Oslo.
These low-risk patients likely don't need the aggressive follow-up called for under current guidelines, Loberg said.
"These findings support more intense surveillance of the high-risk group, but should maybe lead to reconsideration of the guidelines regarding the low-risk group," he said.
The study is published in the Aug. 28 issue of the New England Journal of Medicine.
Current guidelines recommended by the American Cancer Society call for repeat colonoscopy at 5 to 10 years for patients who have one or two small, non-aggressive polyps removed, based on risk factors such as family history and prior health problems.
People with large or aggressive polyps are encouraged to receive repeat colonoscopy every 3 years.
About one-quarter of all colonoscopies performed in the United States are done as increased cancer surveillance for patients who had polyps removed during earlier colonoscopies, said Dr. David Lieberman, chief of gastroenterology at Oregon Health and Science University in Portland, Ore.
"That's a lot of colonoscopy, and if we don't need to do as many, that potentially would free up more resources and enable more screening exams to be done on new patients," Lieberman said.
"These data would suggest a 10-year follow-up would be fine for most patients with low-risk polyps," he added.
The study involved nearly 41,000 patients in Norway who had colorectal polyps removed during a colonoscopy between 1993 and 2007.
Researchers sorted the patients as low-risk or high-risk based on the size of the removed polyp, and whether they had more than one polyp removed. They then tracked how many died from colon cancer through 2011.
Patients in Norway who had a single polyp smaller than 1 centimeter removed during an earlier colonoscopy had a 25 percent reduced chance of death from colon cancer, compared to the general population, researchers found.
At the same time, patients who had multiple polyps or larger polyps removed ran a 16 percent increased risk of colon cancer death.
"As expected, the high-risk group had increased risk of colorectal cancer death compared with the general population, while the low-risk group had a stronger risk reduction," Loberg said. "This really questions the recommendations that are given now" for low-risk patients.
Lieberman noted that since the study took place in Norway, it might not correspond perfectly to America.
For example, Norway had no colon screening program set up during the study period, so the people who underwent colonoscopy likely had symptoms that led doctors to suspect some sort of health problem.
Also, Norway is less ethnically diverse than the United States, which could make a difference, he said.
"It would be important to try to get this kind of information in the United States, to better inform our screening policies," said Lieberman, who wrote an editorial accompanying the study.