Understanding risk factors for colorectal cancer

Important risk factors for colorectal cancer include family and personal medical history, especially:

• Family history of colorectal cancer or hereditary colorectal cancer syndromes. Up to 10% of people with colorectal cancer have inherited a genetic abnormality tied to this illness.
• Personal history of adenomatous polyps or chronic inflammatory bowel disease. Adenomatous polyps of the colon or rectum are noncancerous growths that may develop into cancer if not treated. Chronic inflammatory bowel disease includes ulcerative colitis and Crohn's disease.

Other factors that increase the risk for colorectal cancer, according to the ACS:

• Being of African-American or Eastern European Jewish descent
• Advancing age. About 90% of people with colorectal cancer are 50 or older.
• Lifestyle choices, particularly, a diet high in red meat and processed meat, lack of exercise, and smoking
• Excess alcohol consumption (more than two drinks a day for men and one drink a day for women).
• Obesity
• Having type 2 diabetes

The Importance of screening

Screening is important for preventing colorectal cancer. Screening can find polyps (growths that can become cancer) and remove them before they turn into cancer, the ACS says. Screening can also find cancer early, when it is highly curable.

People who have no other risk factors except advancing age should begin regular screening for colorectal cancer at age 50, according to the ACS and the U.S. Preventive Services Task Force. If you have a family history or other risk factors for colorectal cancer, talk with your health care provider about the need for screening at an earlier age or for more frequent screening. Several screening tests are available, but medical experts differ on which test is better or how often to get screened.

For those who are at least 50 years old and of average risk for colorectal cancer, the ACS recommends:

• A fecal occult blood test (FOBT) or fecal immunochemical test (FIT) every year, or
• A flexible sigmoidoscopy every 5 years, or
• A double-contrast barium enema every 5 years, or
• A colonoscopy every 10 years, or
• A CT colonography (virtual colonoscopy) every 5 years, or
• A stool DNA test every 3 years

The ACS recommends that you begin testing at an earlier age or have more frequent screening if you have any of these risk factors:

• A family history of colorectal cancer. If your parent, sibling or child was diagnosed younger than 60, or you have two immediate family members diagnosed at any age.
• A family history of hereditary colorectal cancer syndromes, such as familial adenomatous polyposis (FAP) or hereditary nonpolyposis colon cancer (HNPCC).
• A personal history of colorectal cancer or adenomatous polyps.
• A personal history of chronic inflammatory bowel disease.

Description of screening tests

Fecal occult blood test (FOBT). This test can find hidden blood in the feces. Small samples of stool are smeared on a card, and a chemical is added to look for a color change that means blood is present. This can mean the presence of polyps or cancers.

Fecal immunochemical test (FIT). This test is similar to a fecal occult blood test, but it doesn't require any restrictions on diet or medications before the test.

Flexible sigmoidoscopy. A slender, flexible, hollow, lighted tube with a small video camera on the end is inserted through the rectum into the lower part of the colon to look for polyps and cancers. Any small polyp found may be removed; polyps, even those that aren't cancerous, eventually may turn into cancer.

Colonoscopy. Just as in the sigmoidoscopy, a slender, flexible, hollow, lighted tube is inserted through the rectum into the colon to look for polyps and cancers, but a colonoscope is longer and allows the healthcare provider to see the entire length of the colon. If a small polyp is found, your provider may remove it. Polyps, even those that are not cancerous, eventually may turn into cancer. This test typically requires deeper anesthesia than a sigmoidoscopy. You will need someone to drive you home afterward. Some people might prefer one of the other screening tests, but if you choose any of the other tests and an abnormality is found, you will likely still need a colonoscopy.

Double-contrast barium enema. Barium sulfate, a chalky substance, is used to partially fill and open up the colon. Air is then pumped in to expand the colon and rectum. An X-ray of the abdomen shows strictures (narrowed areas), obstructions (blockages), and other problems.

CT colonography (virtual colonoscopy). This test uses computerized tomography (CT) scans to examine the colon for polyps or masses. The images are processed by a computer to make a 3-D model of the colon. Virtual colonoscopy is noninvasive, although a small tube must be inserted into the rectum to pump air into the colon.

Stool DNA test. This test looks for specific DNA changes from cancer or polyp cells in the feces. For this test, an entire stool sample is collected and sent off to a lab for testing.

Treatment for colon polyps and colorectal cancer

If your health care provider finds a precancerous polyp, it can be removed during a colonoscopy. If your provider finds cancer, he or she will recommend one of several treatment options. The main types of treatment for colorectal cancer are surgery, radiation therapy, chemotherapy, and targeted therapy, the ACS says. Depending on how advanced the cancer is, treatments may be combined or used one after another.

Reducing your risk for colorectal cancer

You can reduce your risk for colorectal cancer by maintaining a healthy weight and eating a nutritious diet that includes plenty of fruits, vegetables, and whole grains. You should also limit how much red and processed meat you eat. You should quit smoking if you smoke and limit how much alcohol you drink. You should also get regular exercise. The ACS recommends at least 75 minutes of vigorous activity or 150 minutes of moderate physical activity a week.