Colon Cancer Screening: The Test That Can Prevent Cancer Before It Starts

Some immediately start negotiating their way out of it.

During annual physicals, there’s always a moment when I bring up colon cancer screening and my patients give me that look.

But the truth is, colon cancer screening saves lives, and in many cases, it can actually prevent cancer from developing at all.

According to the American Cancer Society, colorectal cancer is the second leading cause of cancer-related death in the United States when men and women are combined. About 1 in 23 men and 1 in 25 women will be diagnosed with colorectal cancer during their lifetime. 

Read that sentence again.

Yes, you read that correctly.

Most people diagnosed with colon cancer are older than 50, but we are seeing more cases in younger adults. Because of this trend, both the American Cancer Society and the U.S. Preventive Services Task Force now recommend starting screening at age 45 for people at average risk. 

This does not include those with a family history, as screening recommendations may depend on the age your family member was diagnosed and their relationship to you.

I strongly encourage all of my patients to stay up to date on their screenings because the stage at diagnosis dramatically changes survival odds.

When colon cancer is detected early — before it spreads beyond the colon — outcomes are dramatically better. Once it has spread to other organs such as the liver or lungs, prognosis becomes much worse.

One of the biggest challenges with colon cancer is that early disease usually causes no symptoms at all.

Symptoms such as unexplained weight loss, rectal bleeding, anemia, or changes in bowel habits often appear later in the disease course, when the tumor has grown larger or spread elsewhere.

This is exactly why screening is so important.

We are looking for cancer before symptoms begin, when it is most treatable.

Fortunately, there are several ways to complete your colon cancer screening.

1. Colonoscopy

This is the gold standard test that all other colon cancer screenings are compared against.

If any of the other screening tests are positive, they ultimately lead to a diagnostic colonoscopy.

For that reason, I often suggest having your first screening done with a colonoscopy if possible.

This is the most invasive screening option.

It involves the dreaded bowel prep the day before, which requires drinking a strong laxative solution to completely clean out the colon.

During the procedure, you are placed under sedation while a gastroenterologist uses a flexible camera to examine the entire colon.

The good news is that when you wake up, the procedure is finished, and you typically go home the same day.

If no abnormalities are found, you generally will not need another screening for 10 years. 

If a polyp is found, it is removed during the procedure and sent to pathology.

Depending on the type of polyp, repeat screening may be recommended in 1, 3, 5, 7, or 10 years.

Some polyps are precancerous and require closer monitoring.

People with a family history of colon cancer may also need screening more frequently.

2. Cologuard

This has become a very popular option in recent years.

My patients lovingly call it the “poop in a box” test — and honestly, that’s exactly what it is.

A kit is mailed to your home.

You collect a stool sample and send it back to the lab for analysis.

The test looks for abnormal DNA markers and microscopic blood that can be associated with colon cancer.

If the test is negative, it should be repeated every three years. 

If the test is positive, the next step is a colonoscopy.

In the large clinical trial that led to FDA approval, Cologuard detected about 92% of colorectal cancers.

However, approximately 13% of people without cancer will still have a positive result, meaning a colonoscopy will be required to confirm the findings.

This test is generally not recommended for people with a history of precancerous polyps, because its ability to detect advanced polyps drops significantly in that population.

3. FIT Test

The fecal immunochemical test, or FIT test, is another stool-based screening option.

This test checks for microscopic blood in the stool, which can sometimes indicate colon cancer or large polyps.

It is simple to complete at home and does not require bowel prep.

The downside is that it is less sensitive than colonoscopy or Cologuard and must be repeated every year to remain effective. 

4. CT Colonography

This test is sometimes called a virtual colonoscopy.

It uses a CT scan to create three-dimensional images of the colon.

A small tube is placed in the rectum to gently inflate the colon with air so that imaging can be performed.

This test still requires bowel prep but does not require sedation.

If a suspicious polyp is found, you will still need a traditional colonoscopy to remove it.

This screening test is typically performed every five years. 

5. Flexible Sigmoidoscopy

Think of this as a mini colonoscopy.

A flexible camera examines the rectum and lower third of the colon.

It is sometimes done in an office setting and usually requires little or no sedation.

The preparation is also lighter — often just an enema the morning of the procedure.

The limitation is that it does not visualize the entire colon, so cancers in the upper colon could be missed.

Flexible sigmoidoscopy is typically recommended every five years, or every ten years when combined with annual FIT testing. 

Final Thoughts

Colon cancer screening might not be the most exciting topic, but it is one of the most powerful tools we have to prevent cancer and save lives.

Many colon cancers start as small polyps that grow slowly over several years.

Screening allows us to find and remove these polyps before they ever become cancer.

If you are 45 or older, talk to your doctor about which screening option is right for you — and most importantly, get screened.