When should screening for colorectal cancer begin?

In general, screening for colorectal cancer should begin at the age of 50, when the risk for developing colorectal polyps and cancer starts to increase. However, if you have a personal or a family history of colorectal polyps or cancer, screening may need to begin before age 50. Men and women should undergo screening since colorectal polyps and cancer affect both genders. Ask your healthcare provider what age is best to start your screening based on your personal risk factors.

What if I have a family history of colorectal cancer?

Your doctor may recommend earlier screening for colorectal cancer if you have a family history of the condition. To determine the appropriate age to start screening, your doctor will discuss all of your risk factors with you. These risk factors can include a family or personal history of polyps, a history of cancer in the abdomen, and a history of inflammatory bowel disease.

What is involved in screening for colorectal cancer?

Several tests are used to screen for colorectal cancer. The following is a list of the most common screening tests. Although colonoscopy is recommended, other options are available.

  • Guaiac-based fecal occult blood test (gFOBT): Similar to the FIT test, the guaiac-based fecal occult blood test also looks for hidden blood in the stool. The specimen (stool) for this test is also collected at home and sent to a lab. In this test, a chemical reaction is used to screen for any hidden blood. However, the gFOBT is unable to determine where in the digestive tract the blood is coming from. Additional testing will be needed to determine the exact location of the blood.
  • Stool tests: This is the least accurate colorectal cancer screening test and it must be done more frequently than other tests. The examination can be done at home and it checks for blood in the stool, which may be caused by large polyps or cancer. If blood is detected on any specimen, a colonoscopy is typically needed.
  • Fecal immunochemical test (FIT): This test looks for blood in the stool that is not easily seen during a stool test. Like the stool test, this can be done at home by collecting stool in tubes. The collected stool will be tested at a lab for any blood.
  • Flexible sigmoidoscopy: A flexible sigmoidoscopy uses a device called a sigmoidoscope to see inside the rectum and lower colon. Unlike the tool used during a colonoscopy, this device is not as long, limiting how much of the colon can be seen. During this procedure, the sigmoidoscope is inserted into the anus and up through the rectum and sigmoid colon (s-shaped part). Air is pumped in during the procedure to allow the caregiver the best possible view. This is a brief outpatient procedure, usually performed without sedation. The bowel must be empty for this procedure—typically done with the help of a laxative the night before the test. Small polyps found during the procedure can be removed and tested for cancer. If these tests come back positive, a colonoscopy will be done.
  • Double contrast barium enema: This is an X-ray examination of the colon and rectum in which barium is given as an enema (through the rectum). Air is then blown into the rectum to expand the colon, producing an outline of the colon on an X-ray. Barium enema is not the most accurate method and should not be the procedure of choice for colorectal cancer screening. It does require a bowel preparation.
  • CT colonography (virtual colonoscopy): In this procedure, also known as CT colonoscopy or virtual colonoscopy, a CT scan (imaging created with the use of X-rays) of the abdomen and pelvis is performed after drinking a contrast dye and inflating air into the rectum. No sedation is needed for this test. Like colonoscopy and barium enema, the colon must be cleaned out before the examination. In the case that a polyp is found, then a colonoscopy must be performed.
  • Colonoscopy: Colonoscopy is the best procedure to check for colorectal polyps and cancer. Colonoscopy is an outpatient procedure in which a physician uses a long, flexible scope (called a colonoscope) to view the rectum and entire colon. During the procedure, small polyps can be removed and tested for signs of cancer. Larger polyps may have a section removed for a biopsy (test of the tissue) to check for cancer. The bowel must be cleaned-out—often done with the help of a laxative—before the procedure begins. The patient is given a sedative for this procedure and will need help getting home afterwards as the sedative wears off. A colonoscopy is considered a safe procedure with few risks.
  • Fecal DNA test: The fecal DNA test works by detecting genetic mutations in the stool. Genetic material, called DNA, is present in every cell of the body, including the cells lining the colon. Normal colon cells and their genetic material are passed with the stool every day. When a colorectal cancer or a large polyp develops, abnormalities (or mutations) occur in the genetic material of the cells. Some mutations present in the polyp or cancer can be detected by laboratory analysis of the stool.

How is colorectal cancer diagnosed?

Colorectal cancer can be diagnosed by a variety of tests. This condition can be diagnosed after you show symptoms or if your caregiver finds something during a screening test that is not normal.

During the diagnosis process, your doctor may do the following tests:

Routine screening tests are done before you show any symptoms. These tests are detailed above.

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