Colon Cancer Screening

A senior couple looks at each other and has coffee while sitting closely together on a couch.

Colon cancer is highly treatable if caught early. That’s why regular screening is important. Screening checks for disease when there are no signs or symptoms.

At the OHSU Knight Cancer Institute, we use a variety of screening tests to spot colon cancer or abnormal clumps of tissue called polyps. Polyps form on the colon's inside surface and can sometimes turn into cancer.

Who should get colon cancer screening?

Risk level

Recommendations are based on your risk level. 

Average risk: You are at average risk of colon cancer if you do not have:

  • A personal history of colon cancer, polyps or inflammatory bowel disease
  • A family history of colon cancer
  • A personal history of radiation to the belly or pelvis to treat cancer
  • Confirmed or suspected familial adenomatous polyposis (FAP) or Lynch syndrome (hereditary non-polyposis colon cancer or HNPCC)

Higher risk: 

  • You have a personal or family history of colon cancer or polyps.
  • You had radiation therapy to the belly or pelvis to treat cancer.

High risk: 

  • You have an inflammatory bowel disease such as Crohn’s disease or ulcerative colitis.
  • You have an inheritied cancer syndrome, such as familial adenomatous polyposis (FAP) or Lynch Syndrome.

Learn more about risk factors on our colon cancer screening page.

If you are at medium risk

American Cancer Society: The American Cancer Society recommends that adults at average risk of colon cancer start regular screening at age 45 and continue regular screening through age 75. If you’re 76 to 85, the organization recommends that you talk with your doctor. It says people over 85 no longer need screening.

OHSU Knight Cancer Institute:  The Knight has preferred and acceptable options to help doctors and patients choose the best option:

  • Preferred option: Colonoscopy every 10 years or a fecal immunochemical test (FIT) every year
  • Acceptable alternatives: 
    • CT colonography every five years
    • FIT and stool DNA test every three years, with an option to add sigmoidoscopy
    • Sigmoidoscopy at five- to 10-year intervals

If you are at higher or high risk

Talk with your doctor to decide what’s best for you.

Colon cancer screening tests


OHSU research shows that colonoscopy is the best way to find colon cancer early.

During a colonoscopy, we use a thin, flexible tube with a camera and light at the tip to examine the length of the colon. If we find polyps, we can often remove them in the same procedure.

An illustration shows how a doctor guides a thin tube through the anus to inspect the rectum and colon. The sedated patient lies on their side.  The colon makes an upside-down U shape. The tube travels vertically up the colon, horizontally as the colon travels across the upper belly, and back down to the lower belly.

Colon Polyps

This illustration shows a section of colon that stretches across the frame before turning down at a right angle. A cross-sectional view shows two polyps growing on the colon’s inside surface. The polyps are red, about the size of peas, and have stems that connect to the colon.
Abnormal growths called polyps can form on the colon’s inside surface. Left untreated, they can turn into cancer.

FIT (fecal immunochemical test)

FIT is a type of fecal occult blood test. It checks stool for “occult” blood, which can’t be seen with the naked eye. Blood in your stool can signal colon cancer or another problem with your digestion.

This is an at-home test. It can be used to diagnose colon cancer when combined with other tests. You can get one from your doctor or buy one at a pharmacy.

OHSU prefers the FIT over other types of fecal occult blood tests because it's sensitive. You can also eat and drink normally beforehand.

Stool DNA test

Like the FIT, this test checks for blood in the stool. It also checks for genetic material that can signal the presence of colon cancer or abnormal tissue called a polyp.

This is an at-home test. To get one, you need a prescription from your doctor.


This is a minimally invasive test. It’s like a colonoscopy. A doctor inserts a thin tube into the rectum to check the rectum and lower colon for tumors or polyps. A colonoscopy checks all of the colon.

Some sedation may be needed. To get a sigmoidoscopy, you need your doctor’s approval. A colonoscopy could be recommended as a next step.

CT colonography

This test is sometimes called a “virtual” colonoscopy. It uses CT (computed tomography) images to check the colon. A health care provider inserts a thin tube into the rectum, which blows air into the colon so the computer can create clearer images.

This test is done at the hospital. Sometimes, you get a drug to relax your bowel muscles.

Blood tests

Tests that detect signs of colon cancer in the blood, including DNA shed by tumors, are for people at average risk. They may be used for people who decline more precise types of screening.

Learn more

For patients

Call 503-494-7999 to:

  • Request an appointment
  • Seek a second opinion
  • Ask questions


Knight Cancer Institute, South Waterfront

Center for Health & Healing, Building 2
3485 S. Bond Ave.
Portland, OR 97239

Free parking for patients and visitors

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