Colorectal cancer is the second-leading cause of cancer death in the US. The primary goal of colorectal cancer screening is to prevent deaths from colon cancer. But the traditional method of screening by the dreaded colonoscopy puts many people off. All that horrid prep the day before…then the actual procedure. Ugh! But now we have options! Let’s take a look at what they are.

Screening overview

Screening for colorectal cancer (CRC, also known as colon cancer or bowel cancer) can help identify cancers at an early and potentially curable stage. It can also prevent the development of cancer by identifying and treating (removing) precancerous growths before they become malignant.  

Until recently, the colonoscopy was the recommended screening test, but now several alternatives are available.

Approximately one third of eligible adults in the US have never undergone screening for CRC. By offering more choice of tests, more people might benefit from regular screening, and more lives saved. The goal is to maximize the total number of people who are screened as that will have the largest effect on reducing CRC death. 

Why colorectal cancer screening works

Most CRCs develop from precancerous polyps. Polyps are growths of the lining of the colon. There are two types of polyps: adenomatous and hyperplastic. The adenomatous polyps can become cancerous; most often their progression to cancer takes 10 years.

CRC screening works by detecting these polyps or early stage cancers and removing them. Regular screening for and removal of polyps can reduce risk of CRC by up to 90%. 

If screening shows that you have an early stage cancer, removal of the cancer by surgery alone (or as part of colonoscopy) typically cures up to 80% of stage 2 colorectal cancers – with no need for chemo and its accompanying side effects. So early detection can lead to cures as well as prevention. 

Who is at higher risk of CRC?

Factors that increase risk include:

  • family history of CRC
  • prior CRC or polyps
  • increasing age (90% of CRC occur in people over 50 years of age with the majority diagnosed between ages 65-74)
  • lifestyle factors 
    • diets high in fat and red or processed meat 
    • diets low in fiber
    • sedentary lifestyle
    • alchohol use
    • cigarette smoking
    • obesity
  • *Very high risk – familial adenomatous polyposis (FAP) – an uncommon inherited condition where CRC occurs before the age of 50, beginning in adolescence
  • *Very high risk – hereditary nonpolyposis colon cancer – also called Lynch syndrome. This is another inherited condition, slightly more common than FAP, but still uncommon.
  • inflammatory bowel disease. People with Crohn disease or ulcerative colitis have an increased risk of CRC.

CRC screening tests available

The US Preventive Services Task Force have recently updated their guidelines stating that screening for CRC should start at the age of 50 and continue until 75. There are now 8 types of screening tests available. The frequency of testing varies according to the test. The tests fall into three main categories: those that are visual, looking at the colon; those that use stool samples; and those that use blood samples. Here is some information on the different types available.

Pros and cons of stool-based and blood-based screening tests

Table of pros and cons of stool and blood based CRC screening from CALMERme.com

Pros and cons of visualization-based screening tests

Table of pros and cons of visualization CRC screening from CALMERme.com

The importance of frequency

One of the key parts of these tests is sticking to the recommended frequency of testing. For example, the colonoscopy test is still the best test in terms of finding polyps and not showing false positive results (that is, the test says there’s something there when there isn’t). This is why the recommendation for testing is only every 10 years (or more frequently if something is found). In comparison, the other tests are less sensitive but by doing them annually or more frequently than a colonoscopy, over ten years you have the same sensitivity.  

Does this make sense? 

For example, if one of the annual stool tests didn’t show a positive result one year when it should have, there is a good likelihood that the positive result will show up the next year and still be appropriate for removal. These cancers are slow growing, so this makes sense.

Remember that the goal is to increase the number of people being screened. The hope is that less invasive colorectal cancer screening tests will increase the likelihood of more people being tested, which in turn will result in fewer deaths from CRC.

Here is a flow diagram that illustrates risk relating to testing and frequency.  

(DCBE mentioned below is a form of X-ray of the colon (like virtual colonoscopy) with a barium enema.)

cog445108-fig1

For more information on these tests and the validation studies performed, check out the information provided by the US Preventive Services Task Force. 

Take home points

With all these options, there’s no excuse for talking ourselves out of getting screened for CRC! You can choose something other than the dreaded colonoscopy and all that colon cleansing. It can be as simple as a blood test.  

Colorectal cancer screening is one type of cancer screening that has shown real benefits. And it can save lives (not to mention avoiding chemotherapy, and all that comes with it).

If you are over 50 and ready for your first screening or due for a follow-up screening, discuss all these options with your doctor, then choose the most appropriate and acceptable test – and just do it!

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