Ask a Health Care Professional – Colorectal Cancer

By Diana Weber, M.D., Medical Director, Blue Cross and Blue Shield of New Mexico

March is national Colorectal Cancer Awareness Month, which draws attention to one of our country’s most deadly but often preventable diseases. Colon cancer, which starts in the large intestine or rectum, is the third leading cause of cancer deaths in both men and women in the U.S. However, when abnormalities that may be precursors to cancer are detected early, they can often be removed before they become a problem.

Colon cancer is an abnormal growth of cells that can occur in the entire length of the colon and rectum. Most colon and rectal cancers start as polyps, which are small growths that are usually benign, meaning not cancerous. There are many types of polyps, some more dangerous than others. Polyps are almost always removed so that they can be examined microscopically by a pathologist to determine whether they are concerning.

People without any known risk factors should begin screening for colon cancer at age 45. The recommendation has in recent years been lowered from age 50 as the incidence of colorectal cancer has increased among younger individuals. Those who remain in good health, without significant life-threatening medical problems, should continue to be screened regularly until age 75. Individuals ages 76 and older should speak with their physicians about how long to continue screening.

Risk factors include a personal history of colon cancer, family history of colon cancer, history of either detection or removal of polyps, diagnosis of inflammatory bowel disease, such as ulcerative colitis or Crohn’s Disease, family history of a hereditary colorectal cancer syndrome, or a history of radiation to the pelvis for other types of cancer.

There are two tests commonly used to screen for colon cancer – stool-based tests, which look for signs of cancer in an individual’s feces, and physical exams, which look at the inner lining of the colon and rectum.

  1. Stool based tests include:
    • Fecal Immunochemical Tests (FIT), which detect abnormalities in the stool. Performed annually.
    • Fecal Occult Blood Tests, which can detect tiny amounts of blood in the stool that cannot be readily seen. Performed annually.
    • Multi-targeted stool DNA test, which looks for abnormal DNA that can be produced by cancers or polyps. Performed every three years.

If any of these tests are abnormal, a colonoscopy will be necessary to complete the evaluation.

  1. Physical examinations include:
    • Colonoscopy, which is the most common physical test to look for polyps and abnormal growths. It consists of inserting a lighted scope with a tiny camera through the anus to see the entire colon and rectum. If the findings are normal, the test should be repeated every 10 years, assuming no symptoms develop.
    • Flexible sigmoidoscopy is similar to a colonoscopy but only examines the rectum and the last few feet of the colon. It may miss abnormalities that are in the first part of the colon. It should be repeated at least every five years.
    • CT colonography, or virtual colonoscopy, is a non-invasive specialized X-ray exam. If an abnormality is found via this test, a colonoscopy will be needed for further evaluation. If this test is normal, it should be repeated every five years.

All of these tests have advantages and disadvantages, so be sure to discuss them with your physician.

Cancer in its early stages often does not cause any symptoms. Late in its development, colon cancer can cause pain, blood in the stool, weight loss, and changes in bowel habits.  However, it is important to detect colon abnormalities long before these symptoms occur.

As with almost any other disease, the risk can be lowered by eating healthful foods that are not overly processed; exercising regularly; maintaining a healthy body weight; avoiding smoking of any kind; and moderating alcohol consumption.

For more information about colorectal cancer, visit the American Cancer Society’s website,

If you have a health question that you would like to be considered in Ask a Health Care Professional, please email [email protected]. BCBSNM will select questions that may appear. Questions will not be personally answered. The opinions expressed in this column are solely those of the author and not necessarily those of BCBSNM. This column is not intended to be a substitute for professional medical care.


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