by Dr. Johanna Chan, Mayo Clinic News Network, Mayo Clinic News Network

colon cancer

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DEAR MAYO CLINIC: A friend of mine passed away recently after receiving a colon cancer diagnosis. Who is at risk for this cancer, and should I be screened?

ANSWER: Colorectal cancer includes colon and rectal cancers, both originating in the lower portion of the large intestine and into the rectum. Estimates are that about 1 in 20 individuals in the U.S. will be diagnosed with colorectal cancer in their life. Men are slightly more likely than women to be diagnosed with colorectal cancer, and African Americans have a higher risk than people of other races.

In the fall of 2020, the U.S. Preventive Services Task Force updated its recommendations for screening for certain populations to start at age 45—five years earlier than the previous recommendation. Colon cancer is one of the only cancers that can be prevented with effective screening.

Previously, colorectal cancer was seen as a disease of aging, particularly since the risk of developing this cancer increases after 50. However, anyone is at risk.

In the past few decades, there has been a growing trend of more young people developing colorectal cancer. Recently, statistics showed an increase in colorectal cancer diagnoses in people 40 to 49, but half of young-onset colorectal cancer patients are under 40. Research is ongoing to determine what factors may be influencing the increased rate of occurrence in a younger population.

There are several additional factors that contribute to the development of colorectal cancer. Risk factors include:

  • Family history

  • Inflammatory bowel disease

  • Diabetes

  • Low-fiber and high-fat diet

  • Radiation therapy for cancer

  • Hereditary colon cancer syndrome

The most common screening is a colonoscopy. The goal of screening is to identify and remove precancerous polyps that may develop into cancer. If polyps are found early and removed, the risk for cancer is reduced. Polyp development can be hereditary.

Recent technological advancements have elevated screening methods. For instance, artificial intelligence (AI) colonoscopy is being used to augment the traditional colonoscopy examination. Specifically, artificial intelligence assists in the identification of potentially dangerous colon polyps. AI colonoscopy has been shown to increase the yield of detecting colon polyps—making colonoscopy even more effective as a cancer prevention tool.

Many people put off colonoscopies for a variety of reasons. In recent years, there have been advancements in screening tests, including some non-invasive options. Certain patients, specifically those considered to be at average risk for cancer, may be candidates for at-home, non-invasive, stool-based testing. Virtual colonoscopy is another non-invasive option that uses CT scanning, but it does still require completion of a bowel preparation. It is important to note that any abnormal finding on a noninvasive screening test warrants further investigation with a diagnostic colonoscopy.

Not knowing your personal risk or family history, I would recommend speaking to your primary health specialist about what screening method may be right for you. Learning whether any family members have a family history of polyps or colon cancer can help identify the best type of screening and how often it should be repeated. Patients found to have a hereditary condition may need to be screened more often. The most common is known as Lynch syndrome, which is an inherited mutation in a gene that increases a person's risk of many kinds of cancer, including colon, ovarian and endometrial.

Be aware of the symptoms of colorectal cancer. These can include abdominal pain; change in normal bowel pattern; unexplained or unintended weight loss; blood in the stool; or dark, tarry stools. Fatigue can result from blood leaking from a tumor and lead to anemia, a decrease in oxygen-carrying hemoglobin that is measured by a blood test.

Though COVID-19 resulted in a decrease in the number of colonoscopies performed, these screenings are the most effective for identifying cancer early. Colon cancer is the only cancer that is preventable.

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