Colon Cancer Screening Tests

Last week we talked about the proposed new guidelines for colorectal cancer screening from the U.S. Preventive Services Task Force (USPSTF), which recommend that screening start at age 45 rather than 50.  We talked about some of the reasons why the recommendation is changing, including the fact that about 12% of colorectal cancers are now diagnosed in people under 50.  Today we’ll talk about some of the ways to screen for colorectal cancer.

What screening tests are done for colorectal cancer?

There are two types of screening tests for colorectal cancer that are recommended by the USPSTF.  Direct visualization tests involve looking directly at the colon and rectum to look for abnormal findings.  Stool-based tests check the stool for signs of cancer.

Stool-based tests include:

• Fecal immunochemical test (FIT) – This test looks for tiny amounts of blood in the stool.
• Guaiac-based fecal occult blood test – This test also looks for hidden blood in the stool through a chemical reaction.
• Stool DNA test – This test looks for hidden blood and abnormal sections of DNA that could be from cancer.

Direct visualization tests include:

• Colonoscopy – A doctor uses a colonoscope (a flexible tube with a light and video camera on the end) to look at the entire length of the rectum and colon.  If the doctor sees anything abnormal or concerning, instruments can go through the tube to take a biopsy of the abnormal area.
• Flexible sigmoidoscopy – This is similar to a colonoscopy, but only examines the rectum, the portion of the colon called the sigmoid colon, and most of the colon on the left side of the abdomen.  This is a little over 1/3 of the amount examined with a colonoscopy.
• CT colonography – This is a special type of CT (Cat) scan, which is used to look for abnormal areas within the colon and rectum.
• How are these tests used?

There are specific screening recommendations regarding which tests to do and how often these tests should be done, depending on your own risk for developing colorectal cancer, as well as your own health and other factors.  Your risk for colorectal cancer depends on things such as your family history, and other factors.  A flexible sigmoidoscopy needs to be done more often than a colonoscopy because it sees less of the colon.  However, it requires less preparation to clean out the bowel, has less risk of complications, and can often be done without anesthetic.  These factors may make it preferred in certain individuals.  

Sometimes a combination of tests is recommended.  For instance, a person at average risk for colorectal cancer may do a flexible sigmoidoscopy every 10 years and have the FIT every 2 years in between.  Some people will have the FIT or guaiac fecal occult blood test done every two years, without having a colonoscopy or sigmoidoscopy.  If there are abnormal findings, then a colonoscopy would be done to investigate the abnormal findings.

Which test is right for you and how often it should be done is something that you should discuss with your family doctor (or GI doctor if you have one).  Your doctor will discuss your family history, and any risk factors that you may have, along with your own medical history and make a recommendation.  You can then discuss with your doctor the risks and benefits regarding the recommendations and make an informed decision about which test (or tests) is best for you.  

As I mentioned last week, we should keep in mind that screening recommendations do not apply to patients who have symptoms that might be caused by colorectal cancer.  In a patient with symptoms, your doctor will recommend tests for the purposes of investigating your symptoms.  These recommendations may be different than those used for screening.  

Any person with persistent symptoms that might be caused by colorectal cancer (which can include rectal bleeding, change in bowel habits, persistent abdominal pain, or pelvic pain), should have these symptoms investigated with appropriate diagnostic tests, even if they are young and have no family history of colorectal cancer.

If you have any questions about colorectal screening tests, please log into your account and send us your question. We are here to help.

Dr. Anita Bennett MD - Health Tip Content Editor

New Colorectal Cancer Screening Recommendations

The U.S. Preventive Services Task Force (USPSTF) recently recommended new guidelines regarding screening for colon cancer.  The new draft guidelines, which were released in late October, recommend that colorectal cancer screening should start at 45.  Let's talk about why the USPSTF wants to change the guidelines.

     

What is the USPSTF?

The USPSTF is an independent, volunteer panel of national experts in disease prevention and evidence-based medicine.  The Task Force works to improve the health of all Americans by making recommendations about preventive medical services based on the latest evidence available.  Before any guidelines are changed, the Task Force issues "draft" guidelines and asks for comments from doctors and the general public regarding the recommendations.  Once the comment time period is over, they consider all of the comments, in addition to the latest evidence, and the final guidelines are published.

What are the current guidelines?

Current recommendations are that people should start screening for colorectal cancer at age 50 and continue screening until they are 75.

The recommended new guideline states that people ages 45 to 75 should be screened for colorectal cancer to reduce their risk of dying from this disease.

What is considered a "screening" test as opposed to a diagnostic test related to colorectal cancer?

A screening test is done on people who do not have any symptoms, specifically targeting people who have a higher likelihood of having cancer, often based on age.  Screening recommendations can vary based on family history or other health conditions. 

If a person comes in complaining of symptoms that could be caused by colorectal cancer, any test to look for this cancer is considered a diagnostic test, rather than a screening test.

The USPSTF has stressed that the draft recommendations "apply to adults without symptoms and who do not have a personal history of colorectal polyps, or a personal or family history of genetic disorders that increase the risk of colorectal cancer."  

Why does the USPSTF want to change the guidelines?

• Colorectal cancer is the third leading cause of cancer deaths in the United States.  The American Cancer Society estimates that there will be 104,610 new cases of colon cancer and 43,340 cases of rectal cancer diagnosed this year.
• Colorectal cancer rates in adults under age 50 have been steadily rising for the last 30 years.  An estimated 12% of colorectal cancer cases this year will be diagnosed in people under age 50.
• Colorectal cancer doesn't always cause symptoms right away.
• Finding the cancer before it causes symptoms, usually means the cancer will be smaller and easier to treat, thus making a cure more likely.  This is important in younger patients who are more likely to be diagnosed at later stages of disease, partially due to no routine screening.
• The USPSTF believes that another reason for later diagnosis in younger patients may be largely due to delayed evaluation of symptoms because colorectal cancer is not typically on the radar of these younger patients or even their doctors.  New guidelines will help emphasize to patients and doctors that colon cancer should be considered in younger patients.
• New guidelines will also help doctors get approval from insurance companies to make screening more affordable for younger patients.

What if a patient younger than 45 has symptoms that might be due to colorectal cancer?

The proposed screening recommendation change to age 45 applies to screening tests only.  This does not apply to patients who have symptoms.  If a person younger than 45, even a person in their 20s, has persistent rectal bleeding, change in bowel habits, or persistent abdominal or pelvic pain, they should discuss these symptoms with their doctor, specifically discussing further diagnostic work up to determine the cause of their symptoms. 

Next week, we will talk more about the symptoms of colorectal cancer that everyone should know, as well as exactly what screening for colorectal cancer involves. 

If you have any questions about colorectal screening, please log into your account and send us your question. We are here to help.

Dr. Anita Bennett MD - Health Tip Content Editor