Which Colorectal Cancer Screening Method Is Right for You?

Colorectal cancer can be deadly, but data show that early screenings are saving lives by detecting it earlier than ever before. And although a colonoscopy is the first-choice method of screening, it’s not the only method that can detect this disease.

Gastroenterologist Brenda Jimenez Cantisano, MD, discusses options for colorectal cancer screenings and how to know which is best for you.

What are the colorectal cancer screening options?

Colon cancer tends to grow slowly, so many people don’t experience any symptoms of the disease in its early stages. But regular screenings can catch problems before they arise.

“The most common screening evaluation is a colonoscopy, which is a short procedure to examine your large bowel,” Dr. Jimenez Cantisano explains. “But there are other ways, too.”

Each has its pros and cons, including overall effectiveness, amount of prep work and time required. Let’s take a look.

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1. Colonoscopy

Of the colorectal cancer screening options, colonoscopy has the highest ability to detect colon cancer and polyps — up to 70%.

This test allows your doctor to see inside your large intestine using a flexible camera called a scope. A colonoscopy checks for symptoms like bleeding, as well as polyps and other possible signs of cancer. And importantly, if your doctor spots a polyp, they can remove it right then and there — during the colonoscopy.

“One of the major benefits of colonoscopy is that we can both detect and remove a polyp,” Dr. Jimenez Cantisano says. “If we see a polyp, we’re able to eliminate it as a potential source of future cancer.”

Also important: A colonoscopy is a one-step test, whereas other tests, like stool-based testing, may require two steps. If, for example, you do a stool-based test and it flags a possible concern, then you’ll need a colonoscopy for further evaluation. (More on this in a moment.)

Before a colonoscopy, your bowels must be completely empty, so there’s some pre-procedure prep work involved. It can be a little unpleasant (translation: lots of pooping), but it’s the key to the procedure being successful.

“If stool is covering or coating the colon, the endoscopist can’t fully visualize the colon,” Dr. Jimenez Cantisano explains. “Some polyps may be missed.”

Most people are sedated during this procedure using conscious (“twilight”) or deep sedation.

2. Virtual colonoscopy (CT colonography)

A virtual colonoscopy is a type of CT scan that allows your provider to look at the inside of the colon. As with a regular colonoscopy, you’ll have to empty your bowels ahead of time, but you don’t have to be sedated during the procedure itself. 

“The downside to virtual colonoscopy is that if your provider finds a polyp, they can’t remove it,” Dr. Jimenez Cantisano points out. “In general, if they spot any abnormalities, you’ll need to have a follow-up colonoscopy.”

Why? Because a virtual colonoscopy itself can’t tell the difference between non-precancerous and precancerous polyps. For this, you’ll need a biopsy (tissue sample), which can’t be done during a virtual colonoscopy. But it can be done during a regular colonoscopy.

3. Flexible sigmoidoscopy

Similar to a colonoscopy, a flexible sigmoidoscopy is an outpatient procedure performed in a medical setting. It also requires prep work to empty your bowels.

Your provider might recommend this procedure if you’re having unexplained symptoms related to your lower colon, rectum and anus. But it isn’t often performed as a screening for colorectal cancer.

That’s because a flexible sigmoidoscopy only evaluates the left side of your colon. It can evaluate conditions like ulcerative colitis, and it can detect polyps — but only on your left side.

“If we find a precancerous growth on your left side, your provider will recommend a second test, like a colonoscopy,” Dr. Jimenez Cantisano says.

Most providers don’t offer flexible sigmoidoscopies as a standard screening for colorectal cancer. But if colonoscopy isn’t an option for some reason, a flexible sigmoidoscopy may be an appropriate stand-in as an initial screening method — especially when combined with a stool test.

4. Stool-based tests

Stool tests for colorectal cancer screenings examine a sample of your poop to identify possible concerns. There are two common types:

• Fecal immunochemical test (FIT) looks for hidden blood in your stool. It can detect early cancer, as well as large, advanced polyps.
• Stool DNA test looks for abnormal DNA associated with polyps and colorectal cancer.

“The benefit of these tests is that you can do them at home,” Dr. Jimenez Cantisano notes. “You don’t need to do any special preparation beforehand, and you don’t have to take time off work or go into an office to have them done.”

Again, though, if these tests come back positive, a colonoscopy will be recommended.

5. Blood tests

In 2024, the U.S. Food and Drug Administration (FDA) approved Shield™, the first blood test to screen for colorectal cancer. It’s for people who are:

• 45 or older
• At average risk
• Not experiencing symptoms

“It’s looking for changes in the bloodstream that might suggest cancer or polyps,” Dr. Jimenez Cantisano explains. “But again, a positive result will require a follow-up colonoscopy. This option is best for patients who do not want to perform any other option, understanding that it’s less effective at detecting precancerous polyps than colonoscopy or stool-based tests.”

Which screening is right for you?

Speak with your healthcare provider to figure out which option is best for you.

To learn about your specific risk factors, they’ll ask about your medical history, family health history, lifestyle habits and more. This information will help determine which test is right for you.

“We do consider colonoscopy to be the gold standard of colorectal cancer screening,” Dr. Jimenez Cantisano reiterates. “But if for some reason you’re not able to undergo a colonoscopy, we have these less invasive screening tests we can turn to.”

When to get a colorectal cancer screening

Here’s a look at general screening guidelines:

• If you’re at average risk: Your risk of colorectal cancer increases as you age, so current guidelines say most people should start being screened at age 45.
• If you’re at high risk: If you have a family history of colon and rectal cancers, talk to your doctor about whether you should be screened earlier than age 45.

The other time you might need earlier screening is if you’re experiencing unexplained symptoms. Talk to your healthcare provider if you have:

• Bloody stool
• Black stool
• Changes in the shape of your stool
• Frequent cramping in your lower belly
• Painful bowel movements
• Rectal bleeding

“In recent years, cases of colorectal cancer have increased significantly in younger adults ages 20 to 49,” Dr. Jimenez Cantisano cautions. “So, it’s vital that you see your doctor if you start experiencing any warning signs of this cancer before you’ve ever been screened.”