New research suggests patients with an average risk of colon cancer may only need to undergo a colonoscopy screening every 15 years instead of the recommended 10.
Swedish researchers found that waiting an extra five years after a first negative colonoscopy carried about the same risk of later having a colorectal diagnosis or dying from the disease as getting screened every 10 years. Extending screening time could reduce “unnecessary invasive examinations,” according to the study published Thursday in JAMA Oncology.
Colorectal cancer is the fourth most common cancer diagnosed in the U.S. and the second most deadly behind lung cancer. The American Cancer Society recommends that screening begin at age 45 for people who don’t have a family history of colorectal cancer or other risk factors, such as inflammatory bowel disease.
In an editorial accompanying the new study, gastroenterologists suggested that future screening guidelines may safely be prolonged for some people, noting that “15 has the potential to be the new 10.”
While rates are going down among people over 50, colorectal cancer diagnoses are on the rise among younger people, opening up a potentially large new group of people who may require colonoscopies.
Doctors are grappling with how to best allocate appointments.
“We do not have enough gastroenterology doctors to do a colonoscopy every 10 years in everyone over 50,” said Dr. Otis Brawley, the Bloomberg distinguished professor of oncology and epidemiology at Johns Hopkins University, who was not associated with the new research.
For the new study, researchers looked at national registry data of more than 110,000 people whose first colonoscopy had a negative result for colorectal cancer. They compared these people with more than 1 million in a control group.
The average age in both groups was 59 years, and about 60% of the patients were female. Taking family history into account, they found that after having a first negative colonoscopy, the risk of later having a colorectal cancer diagnosis or dying from the disease was about the same among people who had a colonoscopy every 10 years and those who stretched it to 15.
They estimated waiting an extra five years between colonoscopies would miss two colorectal cancer cases, and cause one colorectal cancer-related death, for every 1,000 people, while potentially saving 1,000 colonoscopies for other patients.
Employing cheaper, less invasive screening methods 10 to 15 years after a negative colonoscopy could greatly reduce the number of missed screenings, said the study’s lead author, Dr. Mahdi Fallah, head of the Risk Adapted Cancer Prevention Group at the German Cancer Research Center in Heidelberg.
“The best screening test is the one that is actually done. So, if a test like colonoscopy is unaffordable for a person, an alternative cheaper valid test is much better than no test at all,” said Fallah, who is also a visiting professor in the department of clinical sciences at Lund University in Sweden.
More diverse population
The research was conducted in Sweden, which has a mostly white population and a health care system that looks very different from that of the U.S. The national health care system also collects information on the family health history of its citizens, meaning the researchers could be sure those who reported no colorectal cancer in their family were correct.
“It would be really hard to apply these findings to the U.S.,” said Dr. Cassandra Fritz, a gastroenterologist at Washington University in St. Louis. “When we ask patients about colorectal cancer in first-degree relatives, most people don’t know.” Fritz was not involved with the new study.
The U.S. is also much more racially and ethnically diverse, but the research does provide important context that will help doctors understand how they can best delegate their limited resources, Fritz added.
“We need to think about how we can potentially save resources and impact more people with the resources we have,” said Dr. Andrew Chan, a gastroenterologist and director of epidemiology at Massachusetts General Cancer Center in Boston and a co-author of the JAMA editorial.
The proportion of colorectal cancer that occurred in people under age 55 doubled from 1995 to 2019, from 11% to 20%. But the total number of cases in this population is still relatively low.
“Once you get younger than 50, the incidents of colorectal cancer are probably not going to require screening everyone. The risk benefit doesn’t outweigh the cost,” Dr. Robert Bresalier, professor of medicine in the department of gastroenterology hepatology and nutrition at the University of Texas MD Anderson Cancer Center in Houston. Bresalier was not involved with the new research.
That only goes for people without a family history, he added. People who have a parent or sibling who has had colorectal cancer should begin screening 10 years before that parent or sibling was diagnosed, Brawley said.
Other means of screening, mainly stool tests, have been honed to be more precise in recent years. Fecal occult blood tests detect blood in the stool, which can be a warning sign of colon polyps or cancer. FIT-DNA tests, such as Cologuard, detect altered DNA in the stool, which could indicate cancer, and are about 90% effective at detecting cancer, but are less effective at detecting precancerous polyps.
These tests are noninvasive and relatively cheap compared to colonoscopy screening. The catch is, they need to be done more often — every one to three years — than colonoscopy. If the test is positive, the person should get a colonoscopy, which could trigger getting one sooner than every 10 years.
Still, the tests could be a good option for cutting down on the number of colonoscopies given after a negative first screening, Chan said.
“It is important to get screened, but there is a finite number of resources to screen people,” he said. “To screen as many people as we can, we need to make choices about what type of screening we’re doing and how often we’re doing it.”
Better screening in the U.S. will likely be more tailored to risk factors other than age, which experts don’t yet know much about, Bresalier said.
“One size may not fit all. We know a lot about the genetics of colorectal cancer, but most of that research was done in white people. There are potential differences among men and women and among different ethnicities,” he said. “We may get to a point where we get to risk-based intervals even in normal risk people, based on these other factors.”
Warning signs of colon cancer
Symptoms of colorectal cancer often don’t show up until later stages and can be difficult to differentiate from other, less serious conditions.
“You can’t rely on the symptoms,” Chan said. “Many people don’t have symptoms at all and that highlights how important screenings are.”
Having blood in bowel movements, which can appear as red or black, a change in how often you go, abdominal pain and weight loss can all be warning signs of colorectal cancer — and they can also be signs of irritable bowel syndrome, inflammatory bowel disease and a host of other less-serious issues.
Nonetheless, people with new symptoms should make an appointment to see a doctor, Fritz said.
Anyone over age 45 should start getting screened. What that looks like may be determined by where you live.
“In some areas, it’s more feasible to get a colonoscopy than in others. In some areas, it might be more realistic to get a stool-based test,” said Chan.
This includes people living in rural areas or areas without access to a gastroenterologist. For those who are underinsured or uninsured, Fritz said it is possible to pay cash for a stool-based test, though a positive stool test will require a colonoscopy later on.
Something everyone should do is understand their risk, Fritz said.
“A lot of people avoid having conversations about bowel movements, but it’s really important to talk to your family so you know if you are at high risk,” she said.