Colon Cancer Screening: How to Prevent Colon Cancer

Posted on Categories Discover Magazine

In the early stages of colon cancer — the fourth most common cancer in the U.S. and the second-leading cause of cancer deaths — there are usually no obvious symptoms. And yet, if it is caught early, it’s highly treatable.

Thanks to screenings, colon cancer rates have declined steadily among people in their 50s and 60s, says Jeffrey Meyerhardt, a chief clinical research officer at the Dana-Farber Cancer Institute in Boston and professor at Harvard Medical School. At the same time, he says, the rates of colon cancer among people under 50 have steadily increased by nearly 2 percent per year.

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Who Should Get a Colonoscopy?

In response to that increase in younger people, the American Cancer Society and the U.S. Preventative Services Task Force recommend colon cancer screening for those without a family history beginning at age 45. That’s five years earlier than previous recommendations.

Yet only 11 percent of people aged 45 to 49 actually receive that first colonoscopy, considered the gold standard of colon cancer screening tests in the U.S. And about 39 percent of Americans ages 50 to 75 don’t receive colonoscopies as recommended by public health officials, the CDC found.

The American Cancer Society says people list several reasons for not getting a colonoscopy:

  • lack of health insurance or transportation

  • inability to take time off from work

  • belief they don’t need the test since they have no family history or symptoms

  • concern about the cost

  • embarrassment

But people may not realize just how many options are out there.

Tests For Colon Cancer

Colonoscopies are a one-step screening test because the doctor performing the procedure can immediately remove any detectable polyps.

The procedure is good for 10 years for those with average risk, says Hartford HealthCare gastroenterologist Cassidy Alexandre. But for people with a first-degree relative (such as a parent or sibling) who has had colon cancer, doctors recommend beginning screening at 40 and repeating the colonoscopy every five years.

Other screening options are considered two-step tests because if the stool sample comes back positive for potential signs of colon cancer, the patient is then sent for a colonoscopy, Alexandre says. While there are many colonoscopy alternatives available, doctors generally recommend two screening tools the most often: the fecal immunochemical test (FIT) and the stool DNA test.

What Is the FIT Test?

The FIT checks for microscopic blood in the stool, using an antibody that binds to a blood protein called hemoglobin, Alexandre explains. If you have hemoglobin in your stool, that means you also have blood in your stool, he says — which could be a sign of colorectal cancer.

Even if the test comes back negative, doctors recommend repeating it every year if they have not had a colonoscopy.

The FIT test has been shown to effectively detect colorectal cancers, and less so the polyps that are often precursors to colon cancer, says Meyerhardt. “It’s the least sensitive option,” he says, “but it still remains an option.”

What Is the Stool DNA Test?

This test looks for changes in the cells’ DNA, since some DNA changes could signal risk for cancer or the presence of cancer. This test also looks for microscopic blood in the stool.

Cologuard is the only stool DNA test approved for colon cancer screening, Alexandre says. Patients who test negative are advised to repeat every three years.

It’s a good screening technique and a very sensitive test, adds Meyerhardt.

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Less Common Screenings for Colon Cancer

Fecal occult blood test (FOBT) had been used as a screening test in the past but has fallen out of favor with gastroenterologists because of its high number of false positives, explains Alexandre.

Certain foods and medications must be avoided for several days before the test. Additionally, it also fails to detect some polyps and cancers — and if microscopic blood is detected, more tests will likely be needed.

Flex Sigmoidoscopy

With a flexible sigmoidoscopy, doctors look at half of the colon. Patients don’t have to go through the full bowel cleanse prep, as an enema the day of the test is typically sufficient.

The problem with this test, however, is that the majority of people who have polyps or cancer will have them on the right side — and this test examines only the right side, Alexandre says.

What About Virtual Colonoscopies?

For patients who can’t tolerate anesthesia or want to avoid it, such as President Barack Obama while he was in office, there’s also a virtual colonoscopy known as CT colonography.

During this procedure, the patient does the full bowel prep to clean out their colon then drinks a barium liquid to help the doctor see inside. Air is inserted to inflate the colon and expand it to make polyps more visible.

The CT scan allows the doctor to see inside the colon and rectum and look for polyps. This test was more popular 15 years ago than it is now, Meyerhardt says, because “a small polyp won’t be seen.”

Blood Tests for Colon Cancer Screening

There is a blood-based DNA test for an altered gene called SEPT9. This option is FDA-approved for adults 50 and older at average risk for colon cancer who have a history of not completing colon cancer screening tests.

However, according to the National Cancer Institute, there is no evidence that this test can reduce deaths from colorectal cancer.

“Blood-based testing of tumor DNA has emerged as a very powerful tool over the past several years,” says Meyerhardt. “However, there is a lot to still be learned on how to utilize the results both for screening for cancer as well as for treating patients with cancer.”

The FirstSight blood test is one of the multiple tests that are in development, he says, and the initial data from this test are promising for screening for colorectal cancer. “But the sensitivity for advanced adenomas, ones that can eventually become a cancer, is low,” he concludes.

How to Prevent Colon Cancer

One of the most effective ways to prevent colon cancer death is, of course, to get screened regularly, Meyerhardt says.

This is particularly important for Black patients, whose rates of colon cancer are the highest of any racial or ethnic group in the country. African Americans are roughly 20 percent more likely to get colorectal cancer — but they’re also more likely to get it at a younger age, receive late-stage diagnoses and die from it than the general population, Alexandre says.

But there are other ways to lower your risk of contracting the disease in the first place, Alexandre says. These include getting the recommended 150 minutes a week of moderate exercise, maintaining healthy body weight, not smoking, limiting red and processed meats, and limiting alcohol consumption.

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