Colorectal Cancer Screening

What is colorectal cancer screening?

Colorectal cancer screening (or just colon cancer screening) looks for signs of colon cancer before you have symptoms. These tests check your colon and rectum for early-stage cancers polyps. Polyps are abnormal growths that can become cancerous if not removed.

For most individuals, colon cancer screening starts at the age of 45 and continues until age 75. But some people should start screening earlier. If there’s a history of colorectal cancer or other cancers in your family, genetic conditions that increase your cancer risk or if you experience inflammatory bowel disease, ask your healthcare provider about earlier screening.

You may feel squeamish at the thought of getting your colon checked, but screening is well worth it. Colon cancer is the third leading cause of cancer-related deaths in the U.S. But screening can lead to early diagnosis and treatment that can often cure or prevent colon cancer. Colorectal cancer screenings save lives.

How does colorectal screening work?

What happens during a colorectal screening depends on the type of test you and your gastroenterologist decide is best.

Endoscopy tests

The most common colorectal screening test in the U.S. is a colonoscopy. It’s also the most accurate screening method available.

You’ll be sedated or asleep (rare) during the procedure. Your healthcare provider will use a flexible scope with a camera to look for polyps and cancers inside your rectum and colon. The scope also has tools to allow your provider to sample or remove abnormal growths. Afterward, they can test the tissue for cancer cells (biopsy).

If your results are normal, you’ll need a colonoscopy every 10 years. Occasionally, providers recommend shorter follow-ups.

A flexible sigmoidoscopy is another endoscopic test that screens for colon cancer. It’s rarely used in the U.S., as the scope can only access your rectum and the left side of your colon. If your results are normal, you’ll need this procedure every five years. You may need it every 10 years if you have this procedure alongside a stool sample test.

Stool sample tests

For stool sample tests, you use a kit to collect a sample of your stool at home and send it to a lab for testing. The lab will check for blood in your stool. This is because colon cancer and polyps often bleed. Many of these tests can even be sent by mail. Depending on the test, you’ll need to retake it every one to three years if your results are normal.

Types include:

• Fecal immunochemical test (FIT): You’ll collect a single stool sample and send it to a lab within 24 hours.
• Guaiac-based fecal occult blood test (gFOBT): You’ll collect samples from three bowel movements in a row and place them on chemically treated cards. The cards change color if blood is present. You return the cards to a lab.
• Multitarget stool DNA tests with fecal immunochemical testing: You’ll collect a full stool sample and return it within 24 hours. This test checks for traces of blood and genetic mutations that may be signs of colon cancer.

Although these tests aren’t as reliable as a colonoscopy, some people choose them because of the convenience of at-home testing.

Imaging tests

A computed tomography (CT) colonography uses CT scans to piece together detailed, 3D images of your colon. A healthcare provider will analyze the images to check for abnormal growths. If your results are normal, you’ll need this procedure every five years.

This test used to be called a virtual colonoscopy. But unlike an actual colonoscopy, a scope doesn’t go inside your colon. Instead, a machine outside of your body takes pictures of your colon.

How do I prepare for a colorectal screening?

Your healthcare provider will give you detailed instructions about how to prepare. Follow them closely to ensure your results are accurate. In general:

• Endoscopy and imaging tests require food and medication restrictions, as well as bowel preparation to empty your colon. With colonoscopy prep, dietary restrictions start three days before your procedure. You’ll drink a solution that helps you clean out your colon the afternoon or evening before.
• Stool tests require minimal or no preparation. Depending on the test, you may need to avoid certain foods or medications for a few days beforehand.

What are the risks?

The risks of colorectal cancer screening are extremely small, especially when compared to the benefits of detecting cancer early. But procedures that use a scope may cause:

• A perforation (tear) in your colon wall
• Bleeding

Your care team will monitor you after your procedure to ensure you’re OK before you go home.

What do my results mean?

Your results may be normal, which means there are no signs of cancer or precancerous polyps. Or they may be abnormal.

If you have an abnormal result from a stool test, the next step is to get a complete colonoscopy, usually within 60 days.

If your colonoscopy is abnormal, it means your provider found an issue, like signs of cancer or polyps. After removing the suspicious tissue, your provider will send it to the lab for further analysis. Final results usually take one week.

Based on the results, your provider may recommend more frequent colonoscopies to ensure the polyps don’t grow back. If they find cancer, they may also send you to see a surgeon and order more testing.

Sometimes, providers aren’t able to complete the colonoscopy, either because your colon was not well cleaned out or they decided it wasn’t safe to proceed. They may recommend repeating a colonoscopy with a better preparation or another type of screening test.

When should I know the results of my test?

Healthcare providers often go over results immediately after endoscopy and imaging tests. It may take a few days, up to over a week, to get your full results if your provider performed a biopsy during a colonoscopy. Ask your healthcare provider when the lab results should be ready.

For stool tests, the instructions on the kit usually explain how and when you’ll receive your results. If you have questions, reach out to the provider or lab that’s testing your sample.