Diagnosis and Screening:

Colon and rectal cancers can be detected early using the screening tests discussed below. These tests can find precancerous polyps and colorectal cancers at stages early enough for complete removal and cure.

Colorectal Cancer Screening Guidelines

American Cancer Society Recommendations. The American Cancer Society, the American College of Radiology, and the U.S. Multi-Society Task Force on Colorectal Cancer have released joint consensus guidelines for colorectal cancer screening.

These organizations recommend the following test options and schedules for adults age 50 years and older with no significant risk factors for colorectal cancer. Discuss with your doctor which test is most appropriate for you.

• Flexible sigmoidoscopy every 5 years, or
• Colonoscopy every 10 years, or
• Double-contrast barium enema (DCBE) every 5 years, or
• CT colongraphy (CTC), also called virtual colonoscopy, every 5 years

For stool tests, the American Cancer Society recommends the following options. Stool tests must be repeated at regular intervals and a colonoscopy must be performed if stool test results are abnormal.

Stool tests include:

• Guiaiac-based fecal occult blood test (FOBT) with high test sensitivity every year, or
• Fecal immunochemical test (FIT) with high sensitivity every year
• Stool DNA test (sDNA). The frequency of testing has not yet been determined.

U.S. Preventive Services Task Force Recommendations. The U.S. Preventive Services Task Force (USPSTF) has slightly different guidelines. The USPSTF recommends:

• Annual screening with high-sensitivity FOBT, or
• Sigmoidoscopy every 5 years, with high-sensitivity FOBT every 3 years, or
• Colonoscopy every 10 years

These recommendations apply to people ages 50 - 75 with average risk for colorectal cancer. The USPTF does not recommend routine screening for adults ages 76 - 85 years old who have had negative screenings since age 50. The USPTF does not recommend any screening in people over age 85.

According to the USPTF, there is not yet enough evidence to make recommendations for virtual colonoscopy or stool DNA testing.

Guidelines for Increased-Risk Groups. Screening, particularly with colonoscopy, in increased- and high-risk populations can save lives. The most important risk factors are familial adenomatous polyposis (FAP) or hereditary nonpolyposis colorectal cancer (HNPCC), a family history of colorectal cancer or personal history of colorectal cancer, polyps, or chronic inflammatory bowel disease. People with these risk factors should be screened before age 50 and may need more frequent screenings. [For specific screening recommendations for patients with Crohn� ' s disease or ulcerative colitis, see In-Depth Reports #103: Crohn� ' s disease and #69: Ulcerative colitis.]

Description of Screening Tests

Colonoscopy. Colonoscopy allows a doctor to view the entire length of the large intestine using a colonoscope, which is inserted into the rectum and snaked through the intestine. A colonoscope is a long, flexible tube that has a video camera one end. The doctor views images from the colonoscope on a display monitor. The test takes about 30 minutes to perform. If polyps are found, the doctor will remove them. The patient is given a sedative prior to the test, which produces a comfortable “twilight” sleep.

In order for the doctor to perform a successful colonoscopy, the colon and rectum must be completely empty. Your doctor will give you complete instructions for how to prepare during the days preceding the tests, and specific foods and liquids to avoid eating and drinking. The day before the test you will be given laxative solution to clean out the colon. Many people find this cleansing more unpleasant than the colonoscopy itself.

Colonoscopy is generally a safe procedure. In very rare cases, complications such as bowel perforation can occur.

Flexible Sigmoidoscopy. Sigmoidoscopy is similar to colonoscopy but only examines the rectum and the lower two feet of the colon. (In contrast, colonoscopy allows the doctor to view the entire colon.) The procedure takes about 10 - 20 minutes, and sedation is optional. Preparation procedures are less demanding than those for colonoscopy.

Double-Contrast Barium Enema (DCBE). The double-contrast barium enema test uses an x-ray to image the entire large intestine. The test takes about 30 - 45 minutes, and sedation is not required. Preparations are similar to those for colonoscopy and sigmoidoscopy. For the test, barium sulfate is inserted into the rectum using a small, flexible tube. The colon is then pumped with air to help the barium spread through the colon. If polyps are detected in the x-ray, your doctor may recommend you have a colonoscopy for further investigation and removal.

Virtual Colonoscopy. Virtual colonoscopy, also called CT colonoscopy, uses a computed tomography (CT) scan to take three-dimensional images of the colon. The test takes only 10 minutes to perform, and does not require sedation. (It does require the same preparations as other procedures to clean out the colon and bowel.) Air is pumped into the rectum through a small flexible tube. The patient is then slid into a CT scanner, which takes rapid images. Recent studies indicate that CT colonoscopy has a high accuracy rate in detecting adenomas and cancers.

Fecal Occult Blood Test (FOBT). A fecal occult blood test is a take-home test that uses stool samples to detect hidden (occult) blood in feces. It may detect small amounts of blood in your stool from polyps or a tumor, even when your stools appear normal. Your doctor will give you a kit with instructions on how to take stool samples and prepare them for the kit. Your doctor will also inform you about what medications and foods need to be avoided in the days prior to the test. The test kit and samples are sent to a laboratory and results usually come back in a few weeks. If blood is found in the stool samples, you will need to have a colonoscopy.

Fecal Immunochemical Test (FIT). The fecal immunochemical test is a newer type of take-home test for hidden (occult) blood. The test is similar to the fecal occult blood test, but patients do not need to follow medication or dietary restrictions. As with the FOBT, a colonoscopy is recommended if blood is found in the stool.

Stool DNA Test. Like the FIT and the FOBT, the stool DNA test is conducted at home and uses fecal samples. Instead of testing for the presence of blood, this test looks for abnormalities in genetic material that come from cancer or polyp cells. These genetic changes are found in genes such as APC, K-ras, and p53. If DNA mutations are found, a colonoscopy is needed. The stool DNA test is new, and is not yet widely available. Some insurance carriers may not cover its testing.

Diagnosis of Colorectal Cancer

A doctor makes a diagnosis of colorectal cancer based on results of several types of tests. These tests include:

Biopsy. During a colonoscopy, the doctor can remove a tissue sample, which is sent to a laboratory for testing. A biopsy is the only way to definitively diagnose colorectal cancer.

Blood Tests. Blood tests are used to evaluate the red blood cell count and check for anemia. The presence of anemia without any other obvious cause being present will usually require further evaluation of the gastrointestinal tract for a possible cancer. Blood tests are also used to check for specific tumor markers, substances that are released into the blood from cancer cells. Tumor markers include carcinoembryonic antigen (CEA) and CA 19-9. These tests may help your physician follow you for recurrences of colon cancer after treatment. By themselves, they cannot diagnose cancer and are not used as a screening test

Imaging Tests. Various types of imaging tests can help detect the presence of cancer or find out how far the cancer has spread. These tests include ultrasound, chest x-ray, magnetic resonance imaging (MRI) scan, positron emission tomography (PET) scan, and computed tomography (CT) scan.