Should You Start Colorectal Cancer Screening Before Age 50?

Colorectal cancer screening, like most cancer screenings, poses potential downsides along with its benefits. 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, MD, 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."

For those reasons, starting colorectal cancer screening at 50 was the norm for a long time. But in recent years, with rising rates of this cancer in younger adults, the norm has shifted. Today, the major professional medical groups that make recommendations on cancer screenings all generally agree that—unlike a decade ago—the benefits of screening now outweigh the risks for adults starting at age 45. 

There are some slight variations on the advice. The American Cancer Society recommends that all average-risk adults begin colorectal cancer screening at 45. The U.S. Preventive Services Task Force gives screening starting at age 45 a “B” grade recommendation, its second strongest, while screening at age 50 earns an “A” grade. The U.S. Multi-Society Task Force on Colorectal Cancer (MSTF), which represents the American Gastroenterological Association and other professionals, says it “suggests” screening for people ages 45 to 49, while it “strongly recommends” screening starting at age 50. 

In spite of those minor differences, most experts agree that more people should be routinely screened for colorectal cancer, which is the second-leading cause of cancer death in the U.S. In 2021, only about 60 percent of adults older than 45 were up to date with screening.

"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.

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 a 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.