The Importance of Colorectal Cancer Screening

Colorectal cancer is the third most common cancer diagnosed in both women and men in the United States, excluding skin cancer.  

In 2019, it is estimated that there will be 101,420 new cases of colon cancer and 44,180 new cases of rectal cancer. Colorectal cancer is expected to cause approximately 51,020 deaths in 2019.

Although these numbers may seem high, they are actually on the decline.  Why? There are several reasons. Colorectal polyps are being found during routine screenings; the polyps that would otherwise become cancerous are then removed.  In addition, treatment of colorectal cancer is improving.

Screening Guidelines

The American Cancer Society has created guidelines to ensure that adults are screened appropriately for colorectal cancer.  These guidelines are as follows:

  • Those with an average risk of colorectal cancer should begin regular screening at age 45.  
  • Those who are in good health and who have a life expectancy greater than 10 years should continue routine screening through age 75.
  • After age 76, the patient should weigh the pros and cons with their healthcare provider about colorectal screening.  For example, preferences, life expectancy, overall health, and prior screenings should all be considered when deciding whether screening should continue.
  • Those over 85 are not recommended to have routine colorectal cancer screening.

What is average risk?  For screening guidelines, a patient is said to be “average risk” if they do not have the following:

  • A family history of colorectal cancer.
  • A personal history of colorectal cancer or specific types of colon polyps.
  • A personal history of inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease.
  • A personal history of radiation to the abdomen or pelvis to treat prior cancer.
  • A confirmed or suspected colorectal cancer syndrome.  Examples include familial adenomatous polyposis (FAP) and Lynch syndrome (hereditary non-polyposis colon cancer or HNPCC).

What about those at high risk?

Those at high risk for colorectal cancer may need to begin screening prior to age 45.  They may need to be screened more frequently or have more advanced screening. However, the American Cancer Society does not have specific guidelines in place for those who are at increased risk for colorectal cancer.  The American Cancer Society states, “…other professional medical organizations, such as the US Multi-Society Task Force on Colorectal Cancer (USMSTF), do put out such guidelines. These guidelines are complex and are best looked at along with your health care provider.”

Screening Tools

There are a variety of diagnostic tools available to screen for colorectal cancer.  Your healthcare provider will select the right test for you based on a variety of factors.

High-sensitivity fecal occult blood tests (FOBT) screen for blood in the stool.  These tests are useful because polyps and colorectal cancers can bleed.  This screening tool can detect tiny amounts of blood that are not visible otherwise.  There are two types of FOBT available; both are given to the patient as a kit and the samples are returned to the lab.

  • Guaiac FOBT detects heme in the stool, which is a component of hemoglobin.  However, heme can be present in certain foods, like red meat, so there are certain foods that must be avoided for accurate results.
  • Fecal immunochemical test (FIT or iFOBT) uses antibodies to detect hemoglobin in the stool.  

Stool DNA test detects blood in the stool as well as “…nine DNA biomarkers in three genes that have been found in colorectal cancer and precancerous advanced adenomas. The DNA comes from cells in the lining of the colon and rectum that are shed and collect in stool as it passes through the large intestine and rectum.”  Similar to FOBT testing, the stool DNA tests are available as a kit that the patient collects at home. In studies, the stool DNA test detected more colorectal cancers, but also had more false-positive results.

Sigmoidoscopy uses a sigmoidoscope to visualize the rectum and sigmoid colon.  During a sigmoidoscopy, abnormalities can be removed and biopsied.  The colon must be cleared of stool, so a colon preparation is necessary for this test.  Studies indicate that those who have routine sigmoidoscopies after age 50 have a 60 to 70% less risk of death due to colorectal cancer than those who don’t.

Colonoscopy uses a colonoscopy to visualize the entire colon.  Similar to a sigmoidoscopy, abnormalities are removed and biopsied. The entire colon must be cleared of stool, so a colon preparation is necessary for this test; it is more extensive than the preparation for a sigmoidoscopy.  In addition, sedation is received because the testing is more extensive. Virtual colonoscopy is less invasive and uses computed tomography (CT scan) to take pictures of the colon so that abnormalities can be visualized.  However, if abnormalities are seen standard colonoscopy is required.

Symptoms of Colorectal Cancer

Colorectal cancer rarely exhibits symptoms during the early stages of cancer, which is why routine screening is so important.  If early symptoms do occur, they are likely to include:

  • Constipation
  • Diarrhea
  • Blood in the stool
  • Changes in bowel habits
  • Abdominal bloating
  • Stools that are thinner than normal
  • A feeling that the bowels are not emptied completely

These symptoms are often dismissed because they can easily be attributed to other conditions.

Symptoms present themselves during the later stages of cancer, typically in stage II and later.  These symptoms include:

  • Unexplained weight loss
  • Unexplained loss of appetite
  • Nausea and vomiting
  • Jaundice
  • Anemia
  • Weakness
  • Fatigue
  • Change in the frequency of bowel movements, as well as the consistency
  • Constipation
  • Blood in the stools
  • Rectal bleeding
  • A feeling that you are unable to empty the bowels
  • Abdominal pain

If you experience any symptoms that are troubling, you should discuss them with your physician immediately.

Resources

American Cancer Society guideline for colorectal cancer screening. (2018, May 30). Retrieved May 19, 2019, from https://www.cancer.org/cancer/colon-rectal-cancer/detection-diagnosis-staging/acs-recommendations.html

Colorectal cancer symptoms. (n.d.). Retrieved May 19, 2019, from https://www.cancercenter.com/cancer-types/colorectal-cancer/symptoms

Key statistics for colorectal cancer. (2019, January 24). Retrieved May 19, 2019, from https://www.cancer.org/cancer/colon-rectal-cancer/about/key-statistics.html

Tests to detect colorectal cancer and polyps. (2017, July 7). Retrieved May 19, 2019, from https://www.cancer.gov/types/colorectal/screening-fact-sheet

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