how to choose a screening test for colorectal cancer

Colorectal cancer is a leading cause of cancer death in the United States. There are many tests available to screen for colorectal cancer. How do you choose the right screening test for colorectal cancer? Some tests can detect both colorectal cancer and colorectal polyps. Others detect only colorectal cancer. Some tests are invasive while others are non-invasive. Some tests can be used by everyone while others are only available for average-risk persons.

Colonoscopy

Advantages:

  • The only test that can see the entire colon.
  • It can be used to remove polyps.
  • It can be used to remove early stage cancer.

Disadvantages:

  • Requires bowel preparation.
  • Often requires sedation (anesthesia).
  • Invasive.
  • It can lead to certain complications such as bleeding or perforation (tear in the colon).

How often: 

  • Colonoscopy is recommended every 10 years for people at average risk as long as their test results are negative.

Choose screening test:

  • If you have high risk for colorectal polyps or cancer. These include people with family history of colorectal cancer, personal history of colon polyps or cancer, Lynch syndrome or polyposis syndrome. Also, choose if you have inflammatory bowel disease (ulcerative colitis or Crohn’s disease).
  • If you want only one test done since all other tests lead to colonoscopy if they are positive.

Flexible Sigmoidoscopy

Advantages:

  • It can be used to find and remove polyps in the lower part of the colon (the rectum and sigmoid colon).
  • Often does not require sedation (anesthesia).
  • Unlike colonoscopy, it does not require intense bowel cleansing prior to the test. In most cases, all you need is an enema before the procedure.

Disadvantages:

  • It does not look at the entire colon therefore can miss polyp or cancer in the upper part of the colon.
  • Invasive.
  • It can lead to certain complications such as bleeding or perforation (tear in the colon).
  • You still need a colonoscopy if positive.

How often:

  • Every 5 years.

Choose screening test: 

  • If you don’t have access to a colonoscopy.
  • If you have average risk for colorectal polyp or cancer.

Double-contrast Barium Enema (DCBE)

Advantages:

  • Non-invasive.
  • No need for sedation (anesthesia).

Disadvantages:

  • Requires bowel preparation.
  • Exposure to radiation.
  • May miss small or flat colon polyps.
  • The barium used for the test may change your stool color and cause constipation.
  • You still need a colonoscopy if positive.
  • This test is rarely used now in the U.S.

How often:

  • Every 5 years.

Choose screening test: 

  • If a colonoscopy could not be completed in you.
  • If you are mainly interested in knowing if you have a big mass or cancer in the colon.

Computed tomography colonography (CT colonography)

Advantages:

  • Non-invasive.
  • No need for sedation (anesthesia).

Disadvantages:

  • Requires bowel preparation.
  • Exposure to radiation.
  • Looks like the entire abdomen and pelvis thereby picking other findings unrelated to colon polyps or cancer. These findings may lead to unnecessary tests and procedures.
  • May miss small or flat colon polyps.
  • You still need a colonoscopy if positive.

How often:

  • Every 5 years.

Choose screening test: 

  • If a colonoscopy could not be completed in you.
  • If you are mainly interested in knowing if you have a big mass or cancer in the colon.

FOBT (fecal occult blood test)

Advantages:

  • Non-invasive.
  • No need for sedation (anesthesia).
  • No need for bowel preparation.
  • Done at home.

Disadvantages:

  • It cannot differentiate between blood coming from the colon or other parts of the GI tract. It can be positive due to stomach ulcer, colitis, diverticulosis, hemorrhoids.
  • Some foods and medications can affect the result. You need to stop non-steroidal anti-inflammatory agents like ibuprofen 7 days before the test, Vitamin c 3 days before the test and red meat 3 days before the test.
  • You still need a colonoscopy if positive.

How often: 

  • Every year.

Choose screening test: 

  • If you don’t have access to colonoscopy.
  • If you are not a high risk person for colorectal cancer.

FIT (fecal immunochemical test)

Advantages:

  • Non-invasive.
  • No need for sedation (anesthesia).
  • No need for bowel preparation.
  • Done at home.
  • Unlike the FOBT, you do not need to stop certain foods or medications before the test.

Disadvantages:

  • It can be falsely positive.
  • It cannot detect certain polyps (sessile serrated polyps).
  • You still need a colonoscopy if positive.

How often:

  • Every year.

Choose screening test: 

  • If you don’t have access to colonoscopy.
  • If you are not a high risk person for colorectal cancer.

Stool DNA test (Cologuard)

Advantages:

  • Non-invasive.
  • Does not require bowel preparation prior to the test.
  • No need for sedation (anesthesia).
  • Done at home.

Disadvantages:

  • It has a lot of false positives (positive even though there is no polyp or cancer).
  • It is not meant for patients with high risk for colorectal cancer.
  • You still need a colonoscopy if positive.

How often: 

  • Every 3 years.

Choose screening test:

  • If you don’t have access to colonoscopy.
  • If you are not a high risk person for colorectal cancer.