A doctor speaking with someone in his office.

People should begin screening for colorectal cancer at age 45, according to guidelines released last year by the American Cancer Society.

Previous guidance from the ACS, as well as guidelines released by other expert groups in 2016 and 2017, recommended that most people begin screening at age 50. (Most guidelines suggest continuing through age 75, consulting with a doctor about whether to continue to age 85, and stopping colorectal cancer screening after that.)

Why consider getting screened sooner? Research published in 2017 showed that rates of colon and rectal cancer (together called colorectal cancer) were rising among those between 40 and 54 years old. Another study published in 2019 in the journal Cancer confirmed that this trend is continuing.

And in 2020, a large analysis published in JAMA Network Open found a sharp increase in colorectal cancers diagnosed at age 50 versus age 49, suggesting that many people may have had pre-existing cancers that were detected when they began screening at age 50. (A senior author of the analysis received money from companies involved in screening.)

More on Screening

Still, the vast majority of cases are found in people older than 50. 

In 1990, 6 percent of cases of colorectal cancer were diagnosed in people younger than 50; by 2013, that number had risen to 13 percent.

Younger people getting these cancers was part of what fueled a re-examination of the best age to begin screening, says Andrew Wolf, M.D., an associate professor of medicine at the University of Virginia Health System, who chaired the ACS subcommittee that developed the guidelines.

“A 45-year-old today has the same risk of developing colorectal cancer as a 50-year-old did in the 1990s, when we first started recommending that screening begin at age 50,” says Wolf. “A 45-year-old should consider themselves 50 when it comes to colon cancer.” 

When to Screen Is Still Controversial

Not all doctors agree that the age to start these screenings should be lower. Colonoscopy—the most common screening method—is often an uncomfortable process. And it comes with some limited risks, including small but potentially serious punctures in the colon or rectum called perforations. Other screening tests, such as the FIT test (more on this below), can produce false positives that may lead to unnecessary colonoscopies.

“Screening is always a trade-off with benefit and harm,” says Douglas J. Robertson, M.D., M.P.H., chief of gastroenterology at the Veterans Affairs Medical Center in White River Junction, Vt., and a professor at the Geisel School of Medicine at Dartmouth College in Hanover, N.H. “The trade-off is that as you go to younger and younger age groups, the absolute risk for getting or dying from cancer is lower, so more and more people would need to be screened to find the one case of colorectal cancer hiding in these younger age groups.”

Robertson was a part of the U.S. Multi-Society Task Force on Colorectal Cancer (MSTF), representing the American Gastroenterological Association and other professionals, which in 2017 reaffirmed that most people should begin screening at age 50. That mirrors 2016 recommendations from the U.S. Preventive Services Task Force. The group did advise, however, that African Americans—who are at higher risk for colorectal cancer—should begin screening at 45.

There’s not necessarily a simple answer to exactly when to start. Most experts agree, though, that more people should be routinely screened for colorectal cancer, which is the third-leading cause of cancer death in the U.S. In 2015, only about 60 percent of adults older than 50 were up to date with screening.

The ACS guidelines “will encourage physicians and patients to discuss screening potentially at a younger age and then arrive at a decision together,” says David Lieberman, M.D., a professor of medicine in the division of gastroenterology and hepatology at Oregon Health & Science University in Portland, who worked on the MSTF guidelines.

Some people at higher risk—those who smoke, are obese, or have a close family member with colon cancer, for example—may decide to start screening earlier, Lieberman says, and others may choose to wait until age 50.

“We certainly feel that if the conversation starts at 45 and people get screened by 50, that would be a huge step forward,” says Wolf, chair of the ACS subcommittee.

Ultimately, most experts say, it should be a conversation between doctor and patient that takes an individual’s values and priorities into account.

Options for Colorectal Cancer Screening

The ACS guidelines don’t favor any particular screening technique for colorectal cancer, listing several options. (You can read about all of them on the ACS site.)

But the MSTF guidelines take a tiered approach for simplicity, suggesting that patients be presented with two options first—in part to avoid confusion.

Colonoscopy, in which a doctor uses a tube with small camera attached to examine the inside of your colon, remains the gold standard for colorectal cancer screening in the U.S. During a colonoscopy, a doctor can not only detect cancers of the colon and rectum but also remove precancerous polyps that might develop into cancer. Patients generally must drink a liquid laxative to clean out the colon in advance and undergo sedation for the procedure itself. Those who choose this screening method must be screened every 10 years.

The second tier-one option, the fecal immunochemical test (FIT), must be done annually—and a colonoscopy is required as a follow-up if there’s a positive result. FIT is much simpler and less invasive. Using an at-home kit, patients spread a small sample of stool onto a card and mail it in for testing, which looks for signs of hidden bleeding.

Ultimately, “people should be encouraged to choose the test that they are most likely to do,” Robertson says. “The most effective test is the one that gets done.” 

People can also take steps to reduce the risk of colon cancer, including quitting smoking, reducing alcohol consumption, cutting back on processed meat, and getting plenty of fiber and whole grains. Screening alone, experts say, is not enough.