Ten things you need to know about Colon Cancer Screening

Ten things you need to know about Colorectal Cancer (CRC) screening

Colorectal cancer, or colon cancer, occurs in the colon or rectum. Colon cancer, when discovered early, is highly treatable. However, many people are simply afraid of the screening procedures, the prep work and are not well informed. Only 60% of the American adults 50 and older and currently getting screened. Following are ten commonly asked questions on screening procedures for CRC.

  1. Do I really need a colonoscopy? Is it beneficial?  No one in my family has had colon cancer before.

Colonoscopy is an effective procedure and everyone needs to be screened. Colorectal Cancer (CRC) is the third leading cause of non-skin cancers in the US. It is the second leading cause of cancer related deaths in the US. Every one irrespective of race and ethnicity is at risk.

The good news is that when caught on time, it may be completely curable. However if it is let to progress, it is a very difficult cancer to treat.

  1. When should I start screening for colon cancer?

Screening for CRC usually starts at age 50. However, the American College of Physicians and American College of Gastroenterology recommend starting at age 40 to 45 in high risk African Americans. Other guidelines do not have this recommendation

  1. How often should I be screened, or have the test? Is it every 5 years or 7 years or 10 years?

One time testing is insufficient. The incidence of CRC keeps increasing with age up to the age of 90s. If the initial colonoscopy is negative for any abnormalities then the next one is usually recommended in 10 years. However if polyps or other changes are seen then a repeat study can be recommended anywhere from 1 to 5 years.

  1. What if I had a Sigmoidoscopy instead of a Colonoscopy and the study was normal?

In such cases, the study should be repeated in in 5 years. Any time an abnormality is found on sigmoidoscopy, a follow up Colonoscopy should be performed.

If Fecal Occult Blood Testing is used for screening instead of colonoscopy or sigmoidoscopy, then this test needs to be repeated yearly. If any one of the annual test is positive, further testing with Colonoscopy may be necessary.

  1. When do I stop screening?

Screening should continue for most, up to age 75 to 85. When to stop is a decision best made in partnership with your physician. Usually if the life expectancy is less than 10 years, it is recommended to stop.

  1. I have never had a colonoscopy, and I am 80 years old. Should I still get one?

It is important to note that if someone has never had a screening test for colorectal cancer, a one time screening with colonoscopy or sigmoidoscopy is recommended up to ages 83-84. However this is a decision best made after a discussion with your physician.

  1. If the recommended screening is at age 50, there is no need to worry before that age, right?

Risk assessment (history taking by your Primary Care provider) should start at around age 20 and this should be updated periodically, about every 3-5 years.

This is because the individuals at higher risk need to be identified. They may need screening sooner. These are usually individuals with one or more first-degree relatives (parents and or siblings) with CRC that was diagnosed before the age of 60.

Those who have such a family history should be screened at age 40 or 10 years before the diagnosis was made in the first degree relative.

For example, if John’s father or mother was diagnosed with CRC at age 55, then John and his siblings will need screening at age 40, but if his father was diagnosed earlier at age 45, then John will need screening at 35.

There is also a similar increase in risk if there are two second degree relatives with h/o CRC.

  1. Are there any other conditions associated with an increased risk?

Yes. Other high risk groups include those with a personal history of Inflammatory Bowel Disease (Crohn’s colitis, Ulercative Colitis). There is increase in the occurrence of colon cancer in this group of people and they may need earlier and/or more frequent screening.

Another group at higher risk are individuals with past history of childhood cancer and required abdominal radiation therapy.

Also certain genetic syndromes, can predispose to CRC. These include family history of Lynch Syndrome or Heriditary Non polyposis colon cancer, Familial Adenomatous Polyposis. (FAP) and MUTYH associated polyposis. However these account for only around 5% of the CRC cases.

  1. So family history is important, right?

As we have seen there are a few conditions that require an earlier intervention for screening. It is important to know your family history and also any significant past history. This will help you and your Primary Care Physician come up with the correct screening strategy for you.

  1. Is Colon Cancer less likely to affect women?

Colon Cancer is the second leading cause of cancer death in women worldwide. It affects a lot of women too. Overall life time risk of developing colon cancer is 1 in 20 (5%), risk is slightly lower in women, but it still remains one of the leading causes of cancer related death in women.

Following are the test available for CRC Screening

  1. Stool guaiac test, needs to be done yearly. However, this test can have false positives leading to more work up. This test is less expensive and non invasive.
  2. Fecal Immunochemical testing (FIT) is more expensive than guaiac but has fever false positives and therefore fewer follow up studies therefore ultimately may be less expensive.
  3. Stoll DNA test requires collection of entire Bowel movement.  This is a newer procedure and the significance of occurrences of false positive remains unknown at present. Not commonly used.
  4. Flexible Sigmoidoscopy is a test that only identifies disease in the distal 60 cm of the bowel. However, this test requires less patient preparation and does not require patient sedation. If any abnormality is found this should be followed by colonoscopy.
  5. Colonoscopy is good at identifying disease as the whole colon is visualized, done by a GI specialist, who is trained in removing lesions (polyps). Sometimes this serves not only as diagnosis but also as cure if the polyp identified was precancerous or very early in the stage of the disease. However, as it is invasive there is risk of bleeding and perforation with this procedure
  6. CT Colonography gives almost same visual as a colonoscopy and requires prep work.   Newer studies that tag stools may do away with prep work. If any abnormality is found, a colonoscopy is needed.


Screening for Colorectal Cancer: A Guidance Statement From the American College of Physicians. Ann Intern Med. 2012;156:I-30. doi:10.7326/0003-4819-156-5-201203060-00003






Algorithm for Screening: