Colonoscopy and Other Screening Methods for Colon and Rectal Cancer: What You Should Know

MSK gastroenterologists Emmy Ludwig, Robin Mendelsohn, and Hans Gerdes

From left: MSK gastroenterologists Emmy Ludwig, Robin Mendelsohn, and Hans Gerdes

Colorectal cancer is the third most common cancer in both men and women. Unlike many other cancers that do not yet have reliable screening methods, there are a number of ways to detect colon and rectal cancers early, before they cause any symptoms and when they are more likely to be curable.

Below are some frequently asked questions about colorectal cancer screening and advice for getting tested.

Why is it important to be screened for colorectal cancer?

About 140,000 people in the United States are diagnosed with either colon cancer or rectal cancer every year. This translates to a lifetime risk of about one in 22 for men and one in 24 for women. More than 50,000 people in the United States die from colorectal cancer every year.

Survival rates for colorectal cancer have greatly improved in recent years. That’s thanks in large part to tests that detect the disease much earlier than ever before. In addition, colonoscopy screening can actually prevent cancer from developing in the first place by removing growths called polyps before they have a chance to become cancer. MSK biostatistician Ann Zauber, who uses statistical modeling to inform health policy related to colorectal cancer screening, led a study in 2012 that confirmed removal of polyps with colonoscopy actually prevents colorectal cancer deaths.

What are my options for colorectal cancer screening?

There are two major methods of screening for colorectal cancer. The first is to examine the stool for evidence of cancer. The second involves looking inside the colon and rectum.

Of the stool-based tests, the fecal occult blood test (FOBT) and fecal immunochemical test (FIT) both can detect small traces of blood in the stool. Colon or rectal bleeding can be a sign of cancer. A newer test, called Cologuard, looks for both blood and small amounts of tumor DNA.

Imaging tests include colonoscopy, flexible sigmoidoscopy, and virtual colonoscopy (also known as CT colonography). With a colonoscopy, a thin, flexible tube with a light and a video camera on its tip is placed in the colon to search for polyps and cancer. Before the test, you need to prepare by consuming a clear liquid diet and taking a medication to clear out your bowels. Colonoscopy requires you to be sedated during the examination

A flexible sigmoidoscopy is similar to a colonoscopy, except that a doctor uses a shorter tube to examine only the lower part of your colon. It often does not require sedation. In virtual colonoscopy, you still have to undergo the preparation in advance, but the CT scans can be performed while you are awake. “CT colonography is effective for detecting cancer and large polyps, but it’s not as good as colonoscopy at detecting small or flat polyps,” says MSK gastroenterologist Robin Mendelsohn, who focuses on working with people who are at high risk of developing colorectal cancer.

Also, if something is found during a stool-based test or a CT colonography, you still will need to undergo a colonoscopy to diagnose or rule out cancer and remove any polyps that are found.

Who should be screened for colorectal cancer?

Pictured: Moshe Shike & Josephine Abat
Colon Cancer Screening Guidelines
Learn why screening for colon cancer is important. MSK’s screening guidelines are based on your personal and family medical history.
Learn more

MSK’s current guidelines say that if you don’t have a strong family history of colon and rectal cancers or a known genetic predisposition to colorectal cancer, screening should start at age 50. For those who have had regular screenings and never had any polyps found, the tests may not be needed after age 75.

But there are many exceptions to these rules. For example, people who have a strong family history should speak with their doctors about the best age to start screening. This age is largely dependent on when your family members first developed cancer or polyps.

If you have a personal history of colorectal cancer or polyps, you should talk with your doctor about whether you should continue screening past the age of 75.

Finally, for people who have an inherited condition called Lynch syndrome (also known as hereditary nonpolyposis colorectal cancer), experts usually recommend that frequent screenings start as early as while you’re still in your 20s. This condition can be detected through a genetic test.

How often should I get a colonoscopy or other screening test?

It depends on the type of test you get. To be most effective, FOBT and FIT need to be done every year. The current recommendation for the DNA stool test is every three years. But according to Dr. Mendelsohn, the test is still so new — it was approved by the FDA in 2014 — that experts aren’t yet sure about the optimal timing.

For imaging tests, it depends on whether anything is found during the exam. If you have one or two small polyps and they show no signs of being advanced, you should have colonoscopies every five years. If you have three or more polyps or polyps that appear to be more advanced, you should get tested every three years. Otherwise, you need to get screened only once every ten years.

What is the preferred method of screening at MSK?

“Many of us consider colonoscopy to be the gold standard, because there is a capability for both diagnosis and treatment,” Dr. Mendelsohn says. “But I always say the best test is the one that gets done, and gets done well. For people who are unable to undergo colonoscopy, any screening test is better than no test at all.

“Stool tests are much easier for people to take, and they can be done at home,” she adds. “They can improve the prognosis for people with colorectal cancer by detecting early-stage disease that is usually very treatable. But they’re not very good at detecting polyps.”

Many of us consider colonoscopy to be the gold standard, because there is a capability for both diagnosis and treatment.
Robin Mendelsohn gastroenterologist

What are my options if polyps or cancer are found?

If polyps are found during a colonoscopy, they can often be removed right away, while you’re still in the procedure room. Removing them prevents cancer from forming. The polyps will be sent to a pathologist for analysis. Based on the number of polyps and how the cells look under the microscope, your doctor will make recommendations for how often you should have follow-up screenings.

Colon and rectal cancers are much more curable when they’re detected early. For people who do have cancer, advances in drugs and other treatments have improved survival over the past few decades. Today, even some people whose disease has spread to other parts of the body, called metastatic or stage IV cancer, can be cured.

What is MSK doing to promote colorectal cancer screening?

Dr. Mendelsohn, Dr. Zauber, and other members of MSK’s colorectal cancer team have been advisors to the New York City Citywide Colon Cancer Control Coalition, also known as C5. The goal of C5 is to increase the rate of colorectal cancer screening among citizens of New York City, especially members of racial and ethnic minorities that are less likely to get screening.

Women who meet the eligibility requirements can also receive colorectal cancer screening at MSK’s Breast Examination Center of Harlem through the New York State Cancer Screening Program.