Many people undergo a stool test to screen for colon cancer but a new study finds too few follow up with a colonoscopy when that test warns of a possible cancer.
Not following up undermines the point of screening, said study-co-author Jeff Mohl, director of research and analytics for the American Medical Group Association, a trade organization.
In this study of almost 33,000 people at average risk for colon cancer, just 56% who had a positive result from a stool test had followed up with a colonoscopy within a year.
Poorer people and the COVID-19 pandemic were associated with lower follow-up rates.
"Obviously, that's a huge problem," said Mohl. "If you're trying to estimate how many lives are saved, you're assuming that everyone gets follow-ups if they have a positive result, and if half of them don't do that, obviously you'll only save half as many people."
The findings were published Jan. 18 in JAMA Network Open and based on screenings between 2017 and 2020.
"Colorectal cancer is definitely a significant health problem and increasing, particularly in younger patients," said Dr. William Dahut, chief scientific officer with the American Cancer Society. Rates have been increasing by 1% to 2% a year since the mid-1990s in Americans younger than 50, the cancer society says.
The U.S. Preventive Services Task Force recommends that everyone age 45 to 75 undergo colon cancer screening. This can be a stool test, flexible sigmoidoscopy, colonoscopy or CT colonography.
People with higher risk factors, such as inflammatory bowel disease, family history of colon cancer or polyps, or certain genetic syndromes may need to be screened earlier, according to the U.S. Centers for Disease Control and Prevention.
Noninvasive stool-based screening, which is usually done at home, tests your feces for signs of cancer. You can receive either a negative or positive result. A positive finding doesn't guarantee cancer. It might also be that someone has a precancerous colon polyp that should be removed or maybe ate something that triggered the test. False positives are also possible, Mohl said.
"They're not diagnostic. They can't diagnose the condition you have. They just tell you that maybe you're at particularly high risk," Mohl said. In that case, patients should schedule a colonoscopy.
Reasons people might opt for stool screening as a first step over colonoscopy are that a colonoscopy involves sedation and is more time consuming.
Generally, someone getting a colonoscopy needs to take the day off work and arrange transportation home after the procedure.
Sometimes it's hard to get an appointment because there may not be enough providers.
"One of the big factors is just patients being uncomfortable with colonoscopy," Mohl said. "The reasons about why people might do a stool-based test are also reasons why they might not follow up. It's inconvenient. They are weirded out by it or they don't have transportation."
It's also possible some individuals don't understand the significance of a positive stool-based test result.
"If you have a positive stool-based test, you're at roughly 10 times higher risk of having colon cancer, so that it makes it very urgent that you would go in," Mohl said.
At-home tests like this are very important to democratize health care, said Dahut.
"I think it's concerning," Dahut said of the study's results. "Not shocking, sadly, but concerning."
The importance of follow-up colon cancer screening may not be resonating with people in the same way other screenings do, Dahut said, using an abnormal mammogram as an example of screening that might have higher response.
Someone who gets an abnormal mammogram may also have more persistent follow-up from their doctor's office, Dahut said.
"There needs to be an immediate link between a positive test and your colonoscopy," Dahut said. "If you get a positive test, in a perfect world you would then be put into a system where you would be given options for colonoscopy, as opposed to having to just take care of it yourself."
A patient navigator or nurse practitioner might fill that role, Dahut said. "It needs to be done in a way to close that loop up," he added.
One solution may be more provider education, the researchers suggested.
Researchers were also from the cancer detection business Exact Sciences Corporation in Madison, Wis., and the Allegheny Health Network in Pennsylvania.
The U.S. Centers for Disease Control and Prevention has more on colon cancer.
SOURCES: Jeff Mohl, PhD, director, research and analytics, American Medical Group Association, Alexandria, Va.; William Dahut, MD, chief scientific officer, American Cancer Society, Bethesda, Md.; JAMA Network Open, Jan. 18, 2023