Don't Put it Off! - The Importance of Colorectal Cancer Screening

Colorectal cancer, or cancer of the large intestine, is a common and deadly cancer. It is the third most common cancer in both men and women. In the United States, there are around 140,000 new cases of colorectal cancer per year, and more than a third of these people will die from the illness within five years.¹ So, it is prevalent, and deadly.

Fortunately, the number of new cases and death rates for colorectal cancer have been steadily decreasing over the past twenty years.² Part of this is due to increasingly effective treatment options for colorectal cancer, and part is thanks to increased awareness and increased screening. In fact, one study showed that 53% of the reduction in deaths from colorectal cancer could be directly attributed to screening.³ Additionally, the CISNET models estimate that over the course of a lifetime, with screening between ages of 50 to 75, approximately 20 to 24 lives per 1000 could be saved just by screening.⁴ The USPSTF gives their recommendation in favor of colon cancer screening a level “A” recommendation (age 50 and over), which is the highest available, and a level "B" recommendation for the age of 45 through 49. Practically speaking, there is no difference between a level A & B recommendation; this simply means that there is stronger evidence backing an "A" level recommendation.

The new recommended age to begin screening is 45, as of May 18th, 2021. Previously, the usual age to begin screening was age 50 for individuals of average risk. 

There also are some risk factors that can be modified. These include smoking, obesity, inactivity, and heavy alcohol use.⁵ Some risk factors are things you can’t change, however. These include inflammatory bowel disease such as Crohn’s or ulcerative colitis, having a family history for colon cancer, or hereditary polyposis syndromes.⁶ So as always, quitting smoking, avoiding excessive alcohol use, and taking care of your body would be a great idea. Who knew?

Colorectal cancer tends to grow slowly, developing from small protrusions into the inside of the large intestine called polyps. Some polyps are completely benign, and don’t mean much of anything. Other polyps, called adenomas, contain glandular tissue and have the potential to turn into a cancer. These polyps can be removed before they can turn malignant. When they are removed, the tissue is examined under a microscope to look at the characteristics of the cells. Some adenomas contain abnormal cells that are closer to being cancer than others, and these adenomas are called “advanced adenomas”. When you have advanced adenomas, you will need closer surveillance.⁷

Now you have the background. Let’s dive into the main purpose of this article: explaining your screening options.

First of all, you have to know if you are at increased risk. So step one is to answer the following questions:

1. Have you ever personally had colorectal cancer or an “advanced” adenomatous polyp?
2. Have you had one first-degree* family member who had colorectal cancer or an “advanced” adenomatous polyp diagnosed under the age of 60?
3. Have you had two first-degree family member who had colorectal cancer or an “advanced” adenomatous polyp diagnosed at any age?
4. Do you have a history of inflammatory bowel disease (ulcerative colitis or Crohn’s disease)? 
5. Do you have a genetic syndrome that predisposes you to colorectal cancer? (examples include Familial Adenomatous Polyposis, Lynch syndrome, and hereditary nonpolyposis colorectal cancer [HNPCC])
6. Have you received abdominal radiation in the past for previous cancer treatment?

                                               ^{* First degree family members are parents, siblings, and children.}

If you answered no to all of these, you will be considered average risk, and you should begin screening at age 45. 

If you have inflammatory bowel disease, a history of radiation treatments to the abdomen, or a genetic syndrome (a couple of examples are Familial Adenomatous Polyposis and Lynch syndrome), you will need to talk with your doctor to develop a specific screening plan for high-risk individuals.⁸ 

If you have a 1st degree relative who has had colorectal cancer or been diagnosed with an “advanced” adenoma, then it depends on how old they were when they were diagnosed. If they were older than 55, then you should begin screening at the same time as average-risk people (age 45). If you have two first-degree relatives who were previously diagnosed, or one first-degree relative diagnosed before the age of 55 you should begin screening at age 40, or 10 years prior to the age that your relative was when they were diagnosed, whichever is earlier.⁸

So, now that you know when to begin screening, here are your options for screening:⁹

Stool-based tests

• Guaiac-based fecal occult blood test – The gFOBT is a take-home test, where you will need to collect a stool specimen from three different samples, and mail them in for analysis. This is the least expensive option for colon cancer screening, but it’s important to remember that if the test is positive,  then the next step is to undergo a colonoscopy. 
• Fecal immunochemical test – Also known as the FIT test. This is similar to the gFOBT, but is more sensitive at detecting occult blood in the stool. It is more expensive than the gFOBT, but requires specimens from only one stool sample. As with the gFOBT, if the FIT is positive, the follow-up test would be a colonoscopy. 
• FIT-DNA – The FIT-DNA test combines the FIT with targeted analysis of fecal DNA. For this test, the lab will need an entire bowel movement as a sample.

Endoscopic and radiologic examinations

• Colonoscopy - This is a procedure where a camera is navigated from the rectum all the way to the beginning of the large intestine. It has the benefits of direct visualization of the inside of the colon, and being able to remove polyps. This can remove them before they can turn into a cancer. It requires a bowel prep beforehand, where the goal is to “clean out” the bowel so it’s easier to see abnormalities. The negatives of this study include a risk or perforation of the colon with the scope and bleeding. Also, the bowel prep can be somewhat unpleasant. A bowel prep involves fasting for an extended period of time, and “cleaning out” the bowel with different types of laxatives.Most patients will tell me that the prep is far worse than the actual procedure!
• Computed tomography colonography, or "virtual colonoscopy" - This test uses a CT scanner to visualize the colon. With this study there isn’t the risk of perforation as there is with colonoscopy or flexible sigmoidoscopy, but it does involve radiation. Once again, this method does not allow for removal of pre-cancerous polyps. This test still requires a bowel prep.
• Flexible sigmoidoscopy - This is very similar to the colonoscopy, but doesn’t go as far into the colon. This test is sometimes combined with an annual FIT test. This test still requires a bowel prep.

Please refer to this table with a summary of the pros and cons for each screening type. 

And now that you know your options, talk with your doctor and decide which screening option is best for you. Then stay up on your screenings, make the necessary lifestyle changes to decrease your risk, and as always, forward/pass this on to someone that you know and love to help them decrease their risk as well. 

References

1. U.S. Cancer Statistics Working Group. United States Cancer Statistics: 1999–2014 Incidence and Mortality Web-based Report. Atlanta (GA): Department of Health and Human Services, Centers for Disease Control and Prevention, and National Cancer Institute; 2017.
2. Howlader N, Noone AM, Krapcho M, Miller D, Bishop K, Altekruse SF, Kosary CL, Yu M, Ruhl J, Tatalovich Z, Mariotto A, Lewis DR, Chen HS, Feuer EJ, Cronin KA (eds). SEER Cancer Statistics Review, 1975-2013, National Cancer Institute. Bethesda, MD
3. Edwards BK, Ward E, Kohler BA, et al. Annual report to the nation on the status of cancer, 1975-2006, featuring colorectal cancer trends and impact of interventions (risk factors, screening, and treatment) to reduce future rates. Cancer 2010; 116:544.
4. Zauber A, Knudsen A, Rutter CM, Lansdorp-Vogelaar I, Kuntz KM. Evaluating the Benefits and Harms of Colorectal Cancer Screening Strategies: A Collaborative Modeling Approach. AHRQ Publication No. 14-05203-EF-2. Rockville, MD: Agency for Healthcare Research and Quality; 2015.
5. Giovannucci E. Modifiable risk factors for colon cancer. Gastroenterol Clin North Am. 2002;31(4):925–943.
6. Siegel R, Ma J, Zou Z, Jemal A. Cancer statistics, 2014. CA Cancer J Clin. 2014;64(1):9–29
7. Bond JH. Polyp guideline: diagnosis, treatment, and surveillance for patients with colorectal polyps. Practice Parameters Committee of the American College of Gastroenterology. Am J Gastroenterol 2000; 95:3053.
8. Scott D Ramsey, MD, William M Grady, MD. Screening for colorectal cancer in patients with a family history of colorectal cancer. Retrieved from https://www.uptodate.com/contents/screening-for-colorectal-cancer-in-patients-with-a-family-history-of-colorectal-cancer/contributors
9. Chyke Doubeni, MD FRCS, MPH. Screening for colorectal cancer: Strategies in patients at average risk. November 28, 2017. Retrieved from https://www.uptodate.com/contents/screening-for-colorectal-cancer-strategies-in-patients-at-average-risk