Colon Cancer

Can You Be Screened for Colon Cancer Without a Colonoscopy?

Originally published June 24, 2024

Last updated June 24, 2024

Reading Time: 4 minutes

While a colonoscopy is the preferred method, less invasive options can help determine whether there is cause for concern.

A colonoscopy is “clearly the gold standard” screening method for detecting colorectal cancers, advocates Sang Lee, MD, chief of the USC Colorectal Surgery Program, part of Keck Medicine of USC.
The procedure is more than 90% effective, minimally invasive, is usually painless and he says patients aren’t even aware of what’s happening because they are typically put under anesthesia. The American Cancer Society and the U.S. Preventive Services Task Force recommend adults at average risk for colorectal cancer begin routine screenings at age 45. 
However, some patients prefer not to undergo a colonoscopy and the bowel-preparation steps involved, such as restricting eating and consuming clear liquids for a short period of time. Dr. Lee points out that while bowel preparation usually isn’t as inconvenient as some patients think it will be, for those unwilling to undergo a colonoscopy, there are other options they can utilize to get a baseline idea of their colon health.

If you skip having a colonoscopy, what are your other options?

“If a patient is amenable to one of these other methods, that’s better than not screening at all,” acknowledges Dr. Lee, who is also a clinical professor at the Keck School of Medicine of USC.
Other options to screen for colorectal polyps and signs of cancer in either the colon or rectum include:

Finger exam
A digital rectal exam, when the doctor uses their finger to feel for a mass, is appropriate if the patient reports noticeable symptoms like rectal bleeding or a change in bowel function, explains Dr. Lee. “Oftentimes, this exam is enough to diagnose distal rectal cancer.”
Guaiac test
For a guaiac-based fecal occult blood test, the patient provides a stool sample during their in-office visit. The sample is placed on a card that has been coated with the chemical solution guaiac. If the stool contains blood — which can indicate issues including cancer, ulcers, polyps and hemorrhoids — it will quickly change color. 
Fecal immunochemical test
A fecal immunochemical test, or FIT, also analyzes a stool sample for traces of blood. The difference is the patient collects the stool sample at home and submits it for testing. Dr Lee says FIT is about 75% effective in diagnosing colon cancer but only detects about 50% of benign advanced polyps. 
“The whole purpose of screening is to detect polyps before they turn into cancer,” says Dr. Lee. “FIT may miss a lot, so a negative test doesn’t really rule out having advanced polyps that may develop into cancer.”
Cologuard is another test that utilizes stool samples that are collected at home and sent to a lab. This test looks for abnormal DNA in addition to blood in the stool.
“Cologuard will detect colon cancer about 90% of the time, but it can have false positives,” Dr. Lee explains. Like FIT, he warns, Cologuard “is not very good at recognizing those large, advanced polyps. It will detect them maybe 40% of the time.”

What are the signs you need a colonoscopy?

Dr. Lee cautions that these options are recommended only for patients at average risk for colorectal cancer — meaning those without a personal or family history of colorectal cancer and other conditions like inflammatory bowel disease. 
These tests are also not recommended for patients who have experienced symptoms such as blood in the stool, abdominal pain, unexplained weight loss or a noticeable change in their bowel movements. In addition, if any of these tests reveal abnormal findings, the next diagnostic step would be a colonoscopy anyway.
“The advantage of colonoscopies is they allow us to look at the entire colon,” Dr. Lee explains. “They are very sensitive in detecting colon cancer. Plus, we can see the small polyps and remove them before they turn into cancer.”

How often do you need to get a colonoscopy?

For maximum effectiveness, FIT should be repeated annually and Cologuard every three years, says Dr. Lee.
By comparison, most people will undergo a colonoscopy only once every 10 years. Dr. Lee says “colorectal cancer is slow growing,” so if colonoscopy results are normal, patients can usually wait another decade before having their next colonoscopy. 
More frequent follow-ups may be warranted when polyps are found, but Dr. Lee says the frequency varies from patient to patient depending on the diagnosis and risk factors.

At what age do you no longer need a colonoscopy? 

National guidelines recommend regular colorectal screenings through age 75, but Dr. Lee calls this “a bit controversial.” He says in his experience, the decision about whether to continue colonoscopies into your 80s and 90s depends entirely on the health of the individual patient.
“The numerical age doesn’t mean much nowadays because we have much older patients who are very healthy. The oldest patient I’ve ever operated on for colon cancer was 105, and she recovered very well,” says Dr. Lee. 
“If you’re healthy enough to undergo surgery for colorectal cancer, which is obviously a much bigger procedure, wouldn’t you rather have a colonoscopy every few years rather than waiting to see if you develop cancer?” he asks.
Ultimately, Dr. Lee says he reassures his patients that “the idea of a colonoscopy is often more anxiety-provoking than the procedure itself. I’ve had many colonoscopies myself because my father had colon cancer. The bowel prep can be cumbersome, but it’s only once every 10 years.”
He adds, “Colonoscopy is a very safe and effective method to screen for colorectal cancer. And we’ve shown that it is a very effective means to do that. I don’t think patients should be afraid of it. If you’re older than 45, without any risk for colorectal cancer, you should have your screening done.” 

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Erin Laviola
Erin Laviola is a freelance writer for Keck Medicine of USC.