Colorectal Cancer Screening: The Latest Guidelines

David A. Johnson, MD


January 05, 2011


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Screening for Colon Cancer

Hello. I'm Dr. David Johnson, Professor of Medicine and Chief of Gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia. Welcome back to another session of Computer Consult.

Today I thought I could chat with you briefly about colon cancer screening.

A lot is new in this area, and I am sure that questions come up in your primary practice, for example:

  • When do you send a patient to a gastroenterologist or colorectal surgeon for appropriate screening?; and

  • When do you do colon cancer screening and what method do you use?

Let's start with a patient question.

A patient comes in, and during your physical exam, the patient says, "My father had colon cancer," or "My brother had colon polyps."

What are the questions you need to ask before you make the appropriate recommendations for screening this patient?

Screening Recommendations: First-Degree Relatives With Colon Cancer

In the new recommendations,[1] the age cut-off for cancer or advanced adenoma in first-degree relatives is 60 years. I wouldn't call that old anymore, but just recognize that 60 is the age at which we really draw a hard line, where incremental risks begin to justify earlier screening.

If your patient has a first-degree relative with colon cancer at age 60 or older, this represents an average risk, and average risk screening is recommended. If the first-degree relative with colon cancer is under age 60, earlier screening is recommended for the patient.

Now, this is something that is important to understand. Colon cancers begin and then take a couple of years to progress. If somebody comes in, and they have a relative who had colon cancer at age 60.5 years, and it is a more widespread disease, it is more advanced, then I'll fudge it a little bit and make sure that this patient falls in under the earlier screen. But we certainly recognize that patients who have these first-degree relatives who are 60 years or older should be recommended for average risk screening.

Colon Polyps

The same plays out for colon polyps.

If the patient's first-degree relative has had colon polyps diagnosed under the age of 60, then the patient is viewed as high risk. If their first degree relative was older than 60, we say that the patient is of average risk. It is important that these are high-risk adenomas. So now we are asking them to "show me the money, give me the histology." We are asking for documentation that the patient's first-degree relative was diagnosed under the age of 60 with a high-risk polyp. A high-risk adenoma would be 1 cm or greater in size; a large polyp. The polyp must have advanced histology, be it high-grade dysplasia or a villous component.

So, we are asking the patient to go back and, from whoever had the polyp, find out the histology, and confirm that these were, in fact, high-risk adenomas, because there are a lot of people out there with polyps. And, there are a lot of people who are going to continue to come in as family members of people with polyps. Until we really put our arms around the science and say that small, low-grade polyps do not have much incremental risk, we are never going to be able to get the right people in for screening colonoscopy.

So, we put the burden of proof back on the patient. I tell them this is a very important aspect of your healthcare, you have got to help us out. If you cannot get the information, then the recommendation from the national society is that we put you in the average risk category for colon cancer screening.

In the patient population that has a high-risk adenoma in a first-degree relative under the age of 60, we would begin to screen them at an earlier age (40 years) and we would follow them at 5-year intervals. The same is true if they have a relative with colon cancer. We bring them in at 40 years (or 10 years before the age at diagnosis in the youngest affected relative), and we would follow them at 5-year intervals.

Screening Recommendations: Two or More First-Degree Relatives With Colon Cancer

What about patients who have 2 or more first-degree affected relatives over the age of 60?

That recommendation has also changed a little bit in that we would begin screening them at 40 years and we would follow those patients at 5-year intervals.

So, age of onset of adenomas, proof of adenomas, high-risk lesions, and age of onset for polyps or colon cancer are the new, viable thresholds for the questions you need to ask when talking to your patients.

Screening Recommendations: African Americans

Another change since you may have last looked at the guidelines, is that the age of initial screening for African American patients has been moved down to 45 years.

Why is that?

When we looked at the data, and I am a co-author for the national guidelines, it was clear that African American patients present with more advanced cancers or higher-risk adenomas at earlier ages, so the recommendation was just to shift the screening down by 5 years. Begin at 45 years, and then offer the same recommendations for average-risk screening (every 10 years).

Incremental Risk Factors for Colon Cancer

Two situations that were also important to recognize, as far as increased incremental risks (and these are also mentioned in the American College of Gastroenterology Guidelines), are smoking and obesity, something we see all the time.


Smoking adds an incremental risk of nearly 2-3 times for polyps, advanced polyps, and for colon cancer.

We know that the threshold for detrimental effect for association of risks of smoking is 20-pack-years. We know that if you stop smoking, the data extend incremental risks for at least 20 years. So, even the former smoker needs to be considered to be at an increased risk. We know that smokers also have a higher predilection for right-sided cancers and right-sided advanced polyps.

So if you were ever going to beat somebody over the head and say, "You need a colonoscopy", a smoker would certainly be the patient whom I would really push the data on and say this is a significant risk, independent of your age and your average risks, smoking is a significant incremental risk.

We actually considered, in the national guidelines, lowering the screening cut-off age for smokers as well, but it was suggested that it was still somewhat premature to change the screening age for colonoscopy in smokers.


Obesity increases the risk from 1.5 to 3 times, both for polyps and for colon cancer.

We know that fat is metabolically active. We know that it is the pattern of obesity that makes a difference; in colon cancer, it seems to be the abdominal obesity, not the truncal obesity.

The relative risk here is enough to justify pushing the screening recommendation but not enough yet to justify that we should screen these people more definitively, or at an earlier age or more regularly, but just average screening.

Again, just recognize that these 2 patient populations -- smokers and obese patients -- really need to get the message that colon cancer screening is very important.

Screening Strategy Summary

So, hopefully this gives you some strategies, at least, for your next discussions with patients. It is going to take a little time to convince healthcare providers and patients as well, that we really need to better prioritize who we are recommending for these screening strategies. Looking at colonoscopy and the cost implications, we need to stratify the patients who are at highest risk.

So, age over 60, a new threshold in first-degree relatives. Recognize polyps, advanced polyps, the need to have advanced histology or a large size. If you have a family member with advanced polyps, "show me the money, show me the histology," -- it is really important to try to put the onus back on the patient and to make sure that we are not just chasing family history of polyps. Think about African American patients, obese patients, smoking patients; the bottom line here is that we really need to do the right thing.

Fecal Immunochemical Testing

One final comment is the whole issue about fecal immunochemical tests (FIT) replacing fecal occult blood testing.

This is the new standard, and it should be. We know we have doubled the incremental find from using these new improved tests -- the FIT tests -- over the fecal occult guaiac-based tests. These are much more sensitive, and much more specific,[4] and should be the new standard in your practice. You should not be using the old guaiac-based test anymore. The standard is FIT; FIT is the way to go.

We know that we can do better as an overall colon cancer screening coalition, we need to do better as far as selection of patients and in particular in dealing with some of the nuances of patients' concerns about family history and relative risks that need to be put in the appropriate perspective.

So, I'll leave this to your clinical judgment and look forward to discussing another topic with you in the near future.

Thanks for listening, I'm Dr. David Johnson; and I'll see you next time.


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