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Screening for Colorectal Cancer

This section covers the following topics:

Types of colorectal cancer screening

Most colorectal cancers start as an abnormal growth known as a polyp. Although most will never turn into a colorectal cancer, some do have the potential to grow into cancers. The goal of colorectal cancer screening is to find and growths and remove them before they have the chance to turn into cancer. If cancer has already formed, early detection can still help improve a person’s chance of detecting cancer at an earlier, more treatable .

The tests used to screen for colorectal cancer include:

  • colonoscopy
  • flexible sigmoidoscopy
  • colonography
  • stool tests


For this test, the doctor uses a long, flexible tube with a small video camera attached to look at the entire length of the colon and rectum. The patient is placed under sedation while the doctor inserts the tube through the anus into the rectum and colon. The scope has openings for instruments the doctor can use to remove any , which can be examined under a microscope to look for cancer. 

Colonoscopy requires preparation beginning 1-2 days before the exam to empty the colon of any stool.  This allows the doctor to get a good look at the lining of the entire colon during the exam. The doctor prescribes a combination of a liquid diet, laxatives (usually taken as pills or large amount of liquid) and in some cases, enemas. 

Importantly, of all the screenings available, colonoscopy can prevent many cases of colorectal cancer by finding and removing abnormalities before they can become cancer. Although sigmoidoscopy can also find and remove , this procedure uses a shorter scope thImage showing how much of the colon can be examined by colonoscopy compared with signmoidoscopyat doesn’t examine the entire colon. It misses the more aggressive cancers that may develop in the right colon (first part of the colon). Speak with your doctor to decide which screening test is best for you.

Flexible sigmoidoscopy

Flexible sigmoidoscopy is similar to colonoscopy using a flexible tube with a video camera to examine the colon and rectum. Similar to the colonoscopy, the scope has openings for instruments the doctor can use to remove any , which can be examined under a microscope to look for cancer. However, the scope used for sigmoidoscopy is shorter and can only examine the rectum and a small portion of the colon. Most patients don't require sedation for sigmoidoscopy.

As with colonoscopy, sigmoidoscopy requires preparation to empty the colon beginning 1 day before the exam. 


This test uses a type of xray scan known as a  to take detailed, 3-dimensional pictures of the colon and rectum. This test is not as invasive as a colonoscopy, however, it does involve filling the colon and rectum with air using a small, flexible tube. The goal of the scan is to find any . If or abnormalities are found during colonography, a  followup colonoscopy is needed to remove the

This test does not require any sedation. However, the same type of bowel preparation needed for a colonoscopy or sigmoidoscopy is needed 1-2 days before the exam. 

Stool tests

Stool tests look for possible signs of colorectal cancer—such as blood or abnormal —in stool samples. There are several different tests available. These tests require a doctor's prescription. The patient is mailed a test kit, which comes with simple instructions on how to collect the sample and mail it back to the lab. If abnormalities are found during stool tests, a  followup colonoscopy is needed to find and remove any

Colorectal cancer screening guidelines

Experts have different recommendations for screening for people of average risk and high risk for colorectal cancer. The National Comprehensive Cancer Network (NCCN), is an organization of cancer experts that creates guidelines on cancer care and updates them yearly. NCCN recommends that doctors collect personal and family history in order to assess risk for colorectal cancer and make screening recommendations. NCCN has separate guidelines for colorectal cancer screening in people with average risk for colorectal cancer, people with and other inherited mutations. 

Screening for people with inherited mutations

NCCN has separate guidelines for people at increased risk for colorectal cancer due to inherited mutations or other risk factors. Screening guidelines for high risk people involve colonoscopy. The recommended age for beginning screening depends on the gene mutation and, in some cases, personal or family history of cancer or . The NCCN guidelines include screening recommendations for people with inherited mutations in the following genes:

  • Genes associated with  
    • ()
    • ()
    • ()
    •  ()
    • (
  • Other genes associated with colorectal cancer
    • (Peutz-Jegher syndrome)
    • APC (mutations associated with Familial Adenomatous Polyposis or FAP)
    • APC I1307K (this specific variant of the APC gene is found frequently in people of descent. The variant increases the risk for colorectal cancer but not as high as for APC mutations associated with FAP).  
    • BMPR1A
    • SMAD4
    • GREM1
    • MUTYH (guidelines are different for people with a mutation in one vs. both copies of MUTYH)
    • POLD1
    • POLE
    • NTHL1 (guidelines are for people with a mutation in both copies of the gene)
    • MSH3 (guidelines are for people with a mutation in both copies of the gene)

Screening for average risk people

Several organizations publish colorectal cancer screening guidelines for average-risk people. The National Comprehensive Cancer Network (NCCN) and other guidelines recommend that average risk people begin colorectal cancer screening at age 45. According to the guidelines, screening can begin with any of the four types of tests listed above. Each test has benefits and limitations. The frequency of testing depends on the type of test used and whether any or other abnormalities were found on previous tests. 

Find Experts
Find Experts

The following resources can help you locate an expert near you.

Finding gastroenterologists

Other ways to find experts

  • The National Cancer Institute (NCI)-designated comprehensive cancer centers deliver cutting-edge cancer care to patients in communities across the United States. Most centers have specialized screening and prevention centers for high-risk people. Find a center near you and learn about its specific research capabilities, programs, and initiatives.
  • Register for the FORCE Message Boards to get referrals from other members. Once you register, you can post on the Find a Specialist board to connect with other people who share your situation.

Paying For Care
Paying For Care

Colorectal cancer screenings such as stool-based tests (see descriptions below) are considered grade “A” services by the U.S. Preventive Services Task Force (). This means that these services have shown substantial effectiveness in detecting or preventing the disease. 

  • The Patient Protection and Affordable Care Act (ACA) requires that most group health plans, as well as policies sold in the Health Insurance Marketplace and in small group and individual markets, cover 100 percent of one colorectal cancer screening at its recommended frequency (see Colorectal cancer screening tests table below) with no out-of-pocket costs to patients who are age 50 and older—no matter their risk. (The is currently updating its position. The new guidelines, which are under review, propose lowering the recommended starting age to 45.) 
  • Medicare beneficiaries—no matter their age—are allowed one colonoscopy covered at 100 percent every six years for those at average risk and one colonoscopy per 24 months for those at high risk.
  • Medicaid coverage of colorectal cancer screening varies by state. Individuals who qualify based on their state’s decision to expand Medicaid under the ACA are entitled to the same screening and preventive services as those who are covered by private insurance.

For individuals at increased risk, certain states require insurance coverage of colonoscopy beyond that required under the ACA. Check with your state insurance commission to determine if you live in one of these states.

Open Clinical Trials
Open Clinical Trials

The following are studies looking at colorectal cancer screening or prevention.  ​​​​​

Other colorectal cancer screening and prevention studies may be found here.

Last updated December 21, 2022