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Colorectal cancer is caused by an uncontrolled division of abnormal cells in the colon or rectum. It is the third most common cancer in the United States, and it occurs most often in people over the age of 50. This fact sheet answers some commonly asked questions about colorectal cancer screening.

Why Is Screening for Colorectal Cancer So Important?

Many colorectal cancers can be prevented through regular screening. Screening can find precancerous polyps—abnormal growths in the colon or rectum—so that they can be removed before they turn into cancer. Screening is important because when found early, colorectal cancer is highly treatable. Early stages of colorectal cancer usually present no symptoms. Symptoms tend to appear as the cancer progresses.

What Is a Colonoscopy?

A colonoscopy is the best screening test available for colorectal cancer. It is the only screening test that can detect many colorectal cancers. Here are a few things you should know about this test:

  • During a colonoscopy, your doctor examines the lining of your entire colon to check for polyps or tumors. If any polyps are found, they can be removed immediately.

  • On the day of the colonoscopy, you will receive medication to help you relax. Most people fall asleep and do not remember much about the test when they wake up.

  • Your doctor performs a colonoscopy by inserting a long, thin, flexible tube called a colonoscope into your colon through the rectum. The tube has a tiny video camera and light at the end that sends images to a video monitor.

  • Before the procedure, you will receive instructions from your doctor on what to eat and how to empty your bowels.

  • It is generally recommended to start having colonoscopies at age 45, regardless of gender. People at increased risk of colorectal cancer may start earlier, depending on your doctor’s instructions. Your doctor will also tell you when you will need another colonoscopy.

Are Other Screening Tests Available?

If you are unable to have a colonoscopy, your doctor can give you information about alternate tests and how often they should be performed, including:

  • Sigmoidoscopy
  • Double contrast barium enema
  • Virtual colonoscopy (CT colonoscopy)
  • Fecal occult blood test
  • DNA stool tests

You should note that these tests are not as thorough as a colonoscopy. If polyps or tumors are suspected based on these tests, you will still need to have a colonoscopy.

What Are Some of the Risk Factors for Colorectal Cancer?

A risk factor is anything that raises your chances of developing cancer. The following are some of the known risk factors for colorectal cancer. Talk with your doctor about your personal risk and how often you should be screened.

Age. Colorectal cancer is more common in people over the age of 50.

Personal and family history. People who have a parent, sibling or child with colorectal cancer are at a higher risk of developing it themselves, especially if the family member was diagnosed before the age of 60. People who have had colorectal cancer are at higher risk of recurrence (the cancer returning). People with personal or family history of colorectal polyps are also at increased risk of colorectal cancer.

Race. Black and African American individuals are at higher risk. The reasons for this are not fully understood.

Jews of eastern European descent. About 6% of American Jews who are of eastern European descent have DNA changes that increase their risk of colorectal cancer. For more information, ask your doctor about comprehensive biomarker testing, which may include genetic testing for inherited cancer risk.

Inflammatory bowel disease (IBD). IBD, which includes ulcerative colitis and Crohn’s disease, puts you at a higher risk of developing colorectal cancer.

Lifestyle. Being overweight, having an inactive lifestyle, a diet high in red meat and processed meat, smoking and heavy alcohol use can increase your risk of colorectal cancer.

Edited by Marissa Fors, MSW, LCSW, OSW-C, C-ASWCM, CCM

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This fact sheet is supported by Takeda Oncology.

Last updated Monday, October 10, 2022

The information presented in this publication is provided for your general information only. It is not intended as medical advice and should not be relied upon as a substitute for consultations with qualified health professionals who are aware of your specific situation. We encourage you to take information and questions back to your individual health care provider as a way of creating a dialogue and partnership about your cancer and your treatment.

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