When should screening for colorectal cancer begin?
The American Cancer Society recommends that people at average risk of colorectal cancer start regular screening at age 45. Other experts recommend regular screening in average risk individuals to start no later than at age 50. However, if you have a personal or a family history of colorectal polyps or cancer, or inflammatory bowel disease, screening may need to begin before age 45. 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.
Some studies have found that having a first-degree relative with colorectal cancer puts you at a risk that is 2-3 times higher than someone without a first-degree relative with colorectal cancer. A first-degree relative is defined as your mother, your father, your brother or sister, and your child. Your risk can also be higher if you have other people in your family with colorectal cancer, even if they are not first-degree relatives. They could be grandparents, aunts, uncles, cousins, nieces and nephews, even grandchildren.
The age at which any relative is diagnosed is also important. The risk to you is more significant when the relative is diagnosed before age 45.
About 75% of people who do get colorectal cancer do not get it because of genetics. About 10% to 30% do have a family history of the disease.
If you do have relatives that have been diagnosed with colorectal cancer, your healthcare provider may also recommend genetic testing and/or genetic counseling. Certain DNA mutations are inherited and are linked to colorectal cancers. Genetic testing may provide the information needed to know if you are at a higher risk, so that you can have the correct screening at the right time and possibly stop cancer before it develops or at a very early stage.
What is involved in screening for colorectal cancer?
Several tests are used to screen for colorectal cancer. Although colonoscopy is most recommended, other options are available. These are the most common screening tests:
- Fecal immunochemical test (FIT): This test looks for blood in the stool that is not easily seen visually. This test can be done at home by collecting stool in tubes. The collected stool will be tested at a lab for any blood.
- 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.
- Fecal DNA test: The fecal DNA test works by detecting genetic mutations and blood products 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.
- 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). Gas is pumped in during the procedure to allow the caregiver the best possible view. This is a brief outpatient procedure, often performed without sedation. The bowel must be empty for this procedure—typically done with the help of a laxative and or enema beforethe 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.
- 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, polyps can be removed and tested for signs of cancer. The bowel must be cleaned-out—done with the help of a laxative (“bowel preparation”)—before the procedure begins. The patient is usually 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.
- 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 also requires 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 contrast and 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.
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:
- Blood tests (Complete blood count, tumor markers and liver enzymes)
- Imaging tests (X-rays, CT scan, MRI scan, PET scan, ultrasound, angiography)
- Diagnostic colonoscopy (done after you show symptoms, not as a routine screening test)
Routine screening tests are done before you show any symptoms. These tests are detailed above.