Colon Cancer Screening

Cardiology is my specialty, but I love anything related to disease prevention. As an adult cardiologist in the United States, most of the disease that I see is preventable. We have a lot of sayings like “a stitch in time saves nine” or “an ounce of prevention is worth a pound of cure”, but we don’t always live according to these principles. In a country with rising healthcare costs and physician shortages, prevention of disease is going to be a key part of a solution to these problems.

For a number of reasons, I was excited to find out that the American Cancer Society had recently updated their guidelines for screening of colorectal cancer (CRC). I actually see colon cancer quite frequently. We often put patients on blood thinners for various reasons, and sometimes they have an undiagnosed colon cancer that starts bleeding. Additionally, colon cancer and heart disease are not entirely unrelated. Many lifestyle factors that afflict Americans today contribute to the development of both conditions.

Colon cancer is a great target for screening efforts because it is common, deadly, AND very preventable. It is the fourth most common cancer diagnosis in the United States and the second most common cause of cancer death. Additionally, it is usually very slow to develop, so it can be found early on and prevented.

On a personal note, my grandmother died of colon cancer. She lived in India, and didn’t have access to screening tests like most Americans. We are lucky to have the ability to prevent a deadly disease, and I think everyone who has the opportunity to do so should take it. Read the screening recommendations below, and talk to your doctor today!

Colorectal Cancer

The colon and rectum are the last part of the digestive system, where water and some remaining nutrients are absorbed from food that has been digested. Cancer of the colon and rectum increases with age and is associated with genetic predisposition and lifestyle factors. Other risk factors include ulcerative colitis and Crohn’s disease, prior radiation to the abdomen, and cystic fibrosis.

Specific dietary and lifestyle factors can influence the development of colorectal cancer. Obesity and type 2 diabetes are significant risk factors for the development of CRC. As with many other cancers, tobacco and alcohol use also increase the risk of CRC. Most data suggests a small increase in risk associated with processed meat consumption, and less convincing data for red meat consumption.

On the other hand, increased physical activity decreases the risk of CRC. Diets high in fruits and vegetables also appear to decrease the risk. Calcium appears to be beneficial as well, whether due to supplementation or through diet. Overall fiber intake has appeared to be beneficial in some studies, but not in others.

We have a lot of data that aspirin appears to decrease the risk of CRC. This benefit, in addition to cardiovascular benefits, should be weighed against bleeding risk with aspirin therapy. The US Preventative Services Task Force recommends aspirin for those with a 10-year cardiovascular risk over 10%. You can calculate your 10-year risk here and discuss with your physician.

Colon Cancer Screening

The premise behind colon cancer screening is that it generally takes a long time for pre-cancerous cells in the colon to grow into a cancer and eventually spread throughout the body. Cancers start off as small growths called adenomas, which usually take the form of polyps that grow inward from the wall of the colon. These polyps grow over time, and eventually, the cells in them can transform into carcinomas, or cancer. This process takes around 10 years, which gives us a lot of time to detect and treat these growths. Studies have shown that removing these polyps via a procedure called a colonoscopy can prevent cancer.

Guidelines

If you will recall from my discussion of the new cholesterol guidelines: Guidelines are consensus documents put together by really smart, really experienced people who go through a lot of data to provide recommendations on what would be best for most people. They are just that however, guidelines, not rules. Every patient is different, and you and your doctor can figure out what is best for you.

I was struck by how easy the new guidelines were to read and understand. Cardiology guidelines seem much more complicated. Kudos to the authors! The new guidelines were published by the American Cancer Society in 2018. The previous version had been published in 2008.

Ages at which to screen

Interestingly, while the overall rates of colon cancer have decreased over the last ten years (largely due to improved screening), the rates in people under the age of 55 have increased. This is attributed to lifestyle factors such as excess body weight, inactivity, and poor diet (the same factors that have contributed to a rise in obesity, diabetes, and cardiovascular disease in some groups). Based on this finding, one of the big changes in the new guidelines is a recommendation to begin colon cancer screening at the age of 45.

As mentioned above, the increased rates of CRC in younger patients contributed to this recommendation. Additionally, you have to take into account that a cancer diagnosis or death in someone this age, who is in their prime earning years, possibly with young children, can be devastating. The guidelines note that the number of life years saved per colonoscopy in patients aged 40-45 is similar to the number for patients aged 65-69, amongst whom screening is not at all controversial.

The guidelines recommend screening until the age of 75, and then discussing with a physician whether screening should be continued between the ages of 76 and 85.

These recommendations are for patients at average risk. Patients at higher risk should discuss screening with their primary care doctor or a specialist. This includes people with:

• Inflammatory bowel disease (UC or Crohn’s disease)
• A personal history of polyps of CRC
• A family history of CRC
• History of radiation to the abdomen

Types of screening

The guidelines mention different types of screening, but do not specifically recommend one or the other.

The major options in the United States are:

Colonoscopy every 10 years

You may be familiar with a colonoscopy. It requires a bowel prep the night before to clean out your colon – most people say this is the worst part. The procedure itself requires anesthesia and the colon is examined with a long flexible tube. If any polyps are discovered during the procedure, they can often be snared and removed. Larger masses can be biopsied. Because this procedure requires sedation, you will need a ride home after the exam. If any of the other screening tests below is abnormal, it is usually followed up with a colonoscopy.

If you don’t have any polyps, no further testing is recommended for 10 years. If something is found, the gastroenterologist will recommend the timing of a repeat colonoscopy.

Virtual colonoscopy (CT scan) every 5 years

This test also requires a bowel prep to clean out the colon. The colon is filled with air through a short tube inserted into the rectum, and then a CT scan is performed to assess for any polyps or cancers. No sedation is required, and you can drive or return to work afterwards. This test is less likely to pick up some types of polyps than a colonoscopy, so it is recommended to be performed more frequently, once every five years.

Stool based test for blood (fecal immunochemical test – FIT) every year

FIT tests look for hemoglobin in stool. Hemoglobin is the protein in red blood cells that carries oxygen. If it is present in stool, it is suggestive of bleeding from the lower GI tract, as happens with colon polyps and cancer. You apply stool to a card which you will receive and mail it in. Because this test is less likely to detect abnormalities, it is recommended to be performed annually.

Stool based test for cancer DNA every 3 years

A relatively new test uses a stool sample to test for cancer DNA. It also tests for hemoglobin like the FIT test above. You collect a full stool sample at home and mail it in. It is more likely to detect abnormalities than the FIT test alone so the recommended screening interval is less frequent – once every three years.

Summary

Colon cancer is common, deadly, and preventable. It has been increasing in frequency in younger people. The new guidelines recommend screening for colon cancer starting at age 45 in average-risk individuals. Multiple screening options exist. All of these screening tests have different pros and cons, and no one choice is right for everyone. The important thing is to protect yourself and get screened. Talk to your physician today!

Interested in more preventative health topics? Browse the rest of the site, or read about blood pressure, cholesterol, or prediabetes.

Reference: Wolf, A. M., Fontham, E. T., Church, T. R., Flowers, C. R., Guerra, C. E., LaMonte, S. J., Etzioni, R. , McKenna, M. T., Oeffinger, K. C., Shih, Y. T., Walter, L. C., Andrews, K. S., Brawley, O. W., Brooks, D. , Fedewa, S. A., Manassaram‐Baptiste, D. , Siegel, R. L., Wender, R. C. and Smith, R. A. (2018), Colorectal cancer screening for average‐risk adults: 2018 guideline update from the American Cancer Society. CA: A Cancer Journal for Clinicians, 68: 250-281. doi:10.3322/caac.21457