Screening Tests

Screening Tests

If you are at average risk of colorectal cancer, the American Cancer Society recommends all women and men over the age of 50 to undergo one of the following:

• A fecal occult blood test (FOBT) once a year. This must be performed on three separate occasions and you should avoid eating red meat for three days before collecting the stool samples. Your health care professional provides the necessary materials to collect the stool specimens for simple testing at home or in the office. The stool should be collected before it is in the toilet water. This test is recommended annually after age 50 and detects microscopic amounts of blood in the stool. Your health care professional may recommend this test at an earlier age or more frequently if you are at high risk for colon cancer and/or polyps.
• A flexible sigmoidoscopy every five years. Preparing for this test requires administering two enemas two hours before you arrive for the exam. This examination allows the health care professional to inspect the rectum and lining of the left colon with a thin tube with a light and camera on the end. The sigmoidoscope is inserted into the rectum while you lie on your left side. This test is both diagnostic and therapeutic. However, it can detect polyps or cancer accurately in only the last two feet of the large intestine, reducing death rates from colon cancer in this portion of the colon by 60 percent. Unfortunately, the sigmoidoscopy visualizes less than half the colon and misses about half of cancers and polyps that are close to becoming cancer in the first two to three feet of the colon.
• An annual fecal occult blood test (FOBT) or fecal immunochemical test (FIT) and a flexible sigmoidoscopy every five years. FIT and FOBT are similar. FIT is a stool test that also detects hidden blood (occult) in the stool performed similarly to FOBT. However, it is more thorough than FOBT and has fewer false positive results. Some forms of FIT only require two stool specimens versus three for the FOBT, and neither vitamins nor foods will affect FIT results (these things can affect results of a FOBT); therefore, no dietary restrictions are necessary prior to collecting the stool samples. Similar to FOBT, the FIT test will not detect a tumor that is not bleeding, so a colonoscopy may be necessary for further screening or if cancer is suspected. (Of these first three options, the combination of FOBT or FIT every year plus flexible sigmoidoscopy every five years is preferable.)
• A double contrast barium enema every five years. This test involves injecting barium (a liquid imaging agent that shows up during an x-ray) through the rectum into the colon, then taking x-rays of the colon. A health care professional injects the thick, chalky liquid through a small tube inserted into your anus. You may feel an urge to move your bowels, but should hold on while the x-rays are taken. After the x-rays finish, you can expel the liquid. To avoid becoming constipated afterward, you should drink plenty of fluids to flush the barium from your system. While the procedure can be uncomfortable, it is not usually painful. This test is only a diagnostic test. If abnormalities show up on the x-ray, a colonoscopy must be performed. The barium enema is not a very sensitive test and misses half of polyps that are larger than 1 centimeter.
• A colonoscopy every 10 years. Similar to the flexible sigmoidoscope, the colonoscope is a longer thin black tube that allows the health care professional to examine the entire large intestine. Preparation for the procedure requires drinking a laxative recommended the day before the colonoscopy. Adequate preparation is critically important to enable the physician to visualize the entire lining of the colon. Leftover stool obscures the view of that portion of the colon and could lead to missing lesions. The ACS recommends getting a colonoscopy starting at age 50 for the average-risk person or if a FOBT or FIT shows blood in the stool. You typically receive a mild sedative before the procedure, so you should experience minimal discomfort. The procedure itself lasts 15 to 30 minutes.

This test is both diagnostic and therapeutic. It detects both polyps and cancers found anywhere in the colon. Any polyps or other growths found during this examination are usually removed and sent to a laboratory for examination. Medicare now covers this procedure for people over 50 who are considered to be at average risk for developing colon cancer. Women and men over 50 should have a colonoscopy at least every 10 years. The American College of Gastroenterology recommends that African Americans, who tend to develop the disease at a younger age than other races, begin screening by colonoscopy at age 45.

• Virtual colonography. This is a relatively new technique that uses a CT scan to create a three-dimensional image to evaluate the bowel. Not many medical centers have the technology to perform this exam, which is for diagnostic purposes only and the technology is still undergoing development. It does not allow for a biopsy or polyp removal if any abnormalities are found. Most insurance companies do not cover virtual colonography as screening for colorectal cancer.

Most women find sigmoidoscopies and colonoscopies much more tolerable than they expect. Worrying about the process and undergoing the necessary preparation beforehand are often more unpleasant than the exam itself.

Other tests that your health care provider might perform include:

• Digital rectal examination (DRE). Your health care professional inserts a gloved finger into the rectum to feel for any abnormalities. This simple test, which is not painful, can detect many rectal cancers. However, even the longest of fingers are far too short to examine the full length of the large intestine. For this reason, other tests and examinations, such as the FOBT, flexible sigmoidoscopy, and colonoscopy must be used. The rectal exam is not sufficient to screen for colon cancer.
• Genetic testing. The few hereditary cancer syndromes mentioned here are rare but are associated with mutations in specific genes. These mutations can be passed on to other family members. Thus, if your family is affected or may be affected by one of these syndromes, you may need to undergo genetic testing. If genetic testing and counseling are done properly, lives can be changed dramatically, both in terms of preventing colon cancer and lessening the psychological impact of knowing you are predisposed to the disease.

Genetic testing for colon cancer raises may scientific and ethical issues. Although tests are available to identify the mutations that may predispose you for colon cancer, they are not absolutely positive predictors. Additionally, many health care professionals are not yet fully educated about the tests, and may misinterpret the results.

Thus, if you have a strong family history for colon cancer, you should be seen at a genetic screening center. To locate a center, check out hereditary colorectal cancer Web sites such as www.jeffersonhospital.org.

If there is a reason to suspect that you have colorectal cancer, your health care professional will take a complete medical history and perform a physical examination as part of an initial evaluation or "work-up."

Symptoms

Symptoms of colorectal cancer include:

• Change in bowel habits (diarrhea, constipation or narrow stools for more than a few days)
• Urgency for a bowel movement or feeling like you need to move your bowels even if you just did.
• Blood in the stool
• Stomach pain
• Weakness and/or fatigue

Contact your health care professional if you experience one or more of these symptoms.