, by NCI Staff
From the untimely death of “Black Panther” star Chadwick Boseman, to a recent photo essay in GQ magazine, the rapid rise in the rate of colorectal cancer among younger adults has been in the news lately. This increase played a key role in the new recommendation by an independent US advisory panel to start screening for colorectal cancer at age 45 instead of 50.
Screening for colorectal cancer, which can detect cancer and precancerous lesions before symptoms develop, has been shown to reduce deaths from the disease. But while the US Preventive Services Task Force (USPSTF) just updated its guidance to recommend screening for all adults aged 45 to 75, the panel concluded that the “net benefit” of screening after age 75 is small, and did not change its guidance for this age group.
Now, a new study provides some evidence that screening for colorectal cancer appears to be beneficial for people beyond age 75 as well. Although the study’s findings don’t contradict the advisory panel’s screening recommendations for older Americans—that is, that the decision should be made on a case-by-case basis—the researchers believe their results provide helpful information for physicians to use in discussing whether their older patients should get screened for colorectal cancer.
Because the task force suggests that decisions about screening people 76 to 85 years old be made selectively, “it’s been a bit of a gray area for physicians, and for [older] patients, to know what to do,” said Andrew Chan, M.D., M.P.H., a professor of medicine at Massachusetts General Hospital.
Dr. Chan co-led the new study assessing the impact of colorectal cancer screening in more than 56,000 people aged 75 or older. His team found that the risk of dying from colorectal cancer was reduced by more than a third in people over age 75 who had been screened by colonoscopy or sigmoidoscopy, compared with people in the same age group who did not undergo either of these screening tests. The findings were published May 20 in JAMA Oncology.
The study’s results are noteworthy because they provide some of the first real-world evidence suggesting that people might benefit from screening beyond age 75, said Shivan Mehta, M.D., a gastroenterologist and health policy researcher at the University of Pennsylvania, who was not involved with the new study.
Nevertheless, the decision to screen people aged 76 to 85 should still be made on a case-by-case basis by considering the potential benefits and harms for each patient, said Asad Umar, D.V.M., Ph.D., of NCI’s Division of Cancer Prevention, who also was not involved with the new study.
The new findings, which came out after the latest USPSTF guidance was developed, might make physicians a bit more likely to recommend screening for their older patients, “but these recommendations should still be personalized to the patient,” Dr. Mehta said.
Concrete Data from Two Long-Term Studies
In its latest recommendations on colorectal cancer screening, USPSTF concluded that, for people 76 to 85 years old, “patients and clinicians should consider the patient’s overall health, prior screening history, and preferences” in deciding whether screening is appropriate.
The panel’s guidance for people over age 75 is based mainly on studies that use computer modeling to calculate the benefits and harms of screening for people in this age group, Dr. Umar explained.
“There are risks involved with colonoscopy, such as bleeding and perforation of the colon, and also risks involved with the preparation, especially in older people,” Dr. Umar said.
Preparing for a colonoscopy requires a thorough cleansing of the entire colon before the test, which can lead to dehydration and other problems. And the risk of these possible harms tends to be greater in older people, Dr. Umar added.
To get more concrete information on the impact of colorectal cancer screening with colonoscopy or sigmoidoscopy beyond age 75, Dr. Chan’s team used data from two large, long-term studies of US health care professionals, the Nurses’ Health Study and the Health Professionals Follow-up Study. Study participants receive questionnaires every 2 years about their health and health-related behaviors, such as diet and exercise.
From 1988 through 2014, participants were asked whether they had undergone either colonoscopy or sigmoidoscopy in the past 2 years and, if so, why the tests were done.
Colonoscopy examines the inside of the colon using a thin, tube-like instrument with a light and a lens for viewing. Sigmoidoscopy is a similar procedure that examines only the lower part of the colon and involves a less extensive preparation. However, this procedure is not widely available in the United States. Both procedures can be used to remove precancerous lesions, or polyps, if they are detected.
Evidence Suggests Benefits of Screening Beyond Age 75
Among more than 56,000 participants who reached age 75 during the study, the team identified 661 new cases of colorectal cancer and 323 deaths from the disease. They then compared the rates of new colorectal cancer diagnoses and deaths from the disease among participants who reported having a screening colonoscopy or sigmoidoscopy after age 75 and those who did not undergo either test.
There are other, less invasive screening tests for colorectal cancer, but this study “focused on colonoscopy because that has been and continues to be the primary mode of screening” in the United States, Dr. Chan said. And most study participants reported undergoing screening colonoscopies rather than sigmoidoscopies.
Screening after age 75 was linked with a 39% reduction in the incidence of colorectal cancer and a 40% decrease in the risk of death from the disease. The researchers found similar reductions in the risk of death from colorectal cancer, whether or not participants had ever undergone screening before age 75.
Among participants who had a history of cardiovascular disease or multiple underlying health conditions, no clear reduction in colorectal cancer–related deaths was seen with screening. However, these findings were less definitive than the overall results, Dr. Umar said.
“Our data provide additional support for the USPSTF recommendations. And they give people more confidence that if they decide to continue screening beyond age 75, or even to start screening for the first time after age 75, there are data to support that decision,” Dr. Chan said.
More Research Questions to Address
The study’s results are far from the last word on this subject, researchers said. Because this was an observational study, “it is not completely clear if the improved outcomes are from the screening [test] or from the selection of patients to get screened,” Dr. Mehta said.
The researchers could not account for factors that may have influenced doctors’ decisions on whether to suggest screening to certain patients and people’s decisions to undergo screening, he explained.
For example, because colonoscopy is invasive and the preparation can be difficult, it’s possible that only the older participants who were fit and healthy underwent this screening test. And that could explain the lower death rate seen in the group that was screened.
Additional studies will be needed to guide future recommendations on colorectal cancer screening in older adults, Dr. Umar said.
“I hope we will reach a point where we can start to think about more sophisticated ways [than a person’s age] to help guide” decisions about colorectal cancer screening—for example, by looking at certain lifestyle factors or genetic risk factors that predispose some people to the disease, Dr. Chan said.
Although this study focused on colonoscopy, “there is increasing evidence of the value of noninvasive screening tests for colorectal cancer, such as stool-based testing,” which people can do at home and don’t require cleansing the colon, Dr. Chan said. “And how those tests fit into screening recommendations for people over age 75 remains an area for future research.”
Studying the role that stool tests may play in screening people of all screening-eligible ages will also be important because the number of specialists (gastroenterologists) in the United States available to do colonoscopies for people aged 45 to 75 is already limited, Dr. Umar said.
Finally, because most participants in the new study were White, the investigators note the need for studies in older people of other racial and ethnic groups to see if disparities in the benefits of screening exist between groups.
“To date, we’ve seen that the impact of screening on colorectal cancer rates and mortality appear to be consistent across different racial and ethnic groups,” Dr. Chan said. But “additional real-world data will always be welcome.”