Colorectal Cancer Detection and Diagnosis
We may detect colorectal cancer by one of the following tests, as recommended by the American Cancer Society for men and women age 50 and over:
Tests that detect adenomatous polyps and cancer:
- Colonoscopy every 10 years (this is the preferred test and it views the entire colon). This is the only test that examines the entire colon and allows removal of precancerous polyps. It is the screening method of choice and the gold standard of colorectal cancer screening.
- Flexible sigmoidoscopy every five years (this test views the lower one-third of the colon, if abnormal results are found a colonoscopy may be recommended)
- Double-contrast barium enema every five years (if one or more larger polyps are observed colonoscopy will be recommended)
- Virtual colonoscopy (CT colonography) every five years (if one or more larger polyps are observed colonoscopy will be recommended)
Tests that primarily detect cancer:
Fecal occult blood test (FOBT) yearly
- Guaiac fecal occult blood test
- Fecal immunochemical test (FIT)\
- Stool DNA test, frequency uncertain (this test detects abnormal DNA from cells passed in the stool)
If either of these tests is positive, a colonoscopy may be recommended.
If you’re at an increased risk of colorectal cancer because of family history or certain medical conditions, you should begin screening before age 50 and/or have more frequent screenings. You should discuss this with your physician.
Colorectal Cancer Diagnosis
Most colon cancers arise from polyps that are growths on the lining of your colon. These polyps are benign when they first appear. Some polyps can grow and turn into cancer over a period of time. The type of polyp most likely to become cancer is called an adenoma. These polyps arise from glandular cells that line the colon. It can take years before a polyp changes from an adenoma to cancer.
Cancer can occur in any part of the colon, but most often it occurs in the lower part of the colon known as the descending colon. Cancer that arises in the rectum is called rectal cancer. Colon cancer and rectal cancer are often referred to as colorectal cancer.
If there is reason to suspect that you have colon or rectal cancer, your doctor will take a complete medical history and do a physical exam. One or more of the following tests will be done to determine if colorectal cancer is really present.
Diagnostic Tests for Colorectal Cancer
Colonoscopy: a colonoscopy is a procedure where your doctor can closely check the lining of the entire colon (large bowel). A flexible tube (about the thickness of your finger) is passed into the anus and advanced slowly into the rectum and colon. Polyps can be removed and biopsies taken to rule out cancer.
Flexible Sigmoidoscopy: Flexible Sigmoidoscopy is a test that allows your doctor to closely check the lining of the rectum and a part of the colon. It checks the lower one-third of the colon. (large bowel). A flexible tube (sigmoidoscope) is put into the rectum and slowly moved to the sigmoid colon. Polyps can be removed and biopsies taken to rule out cancer.
Double Contrast Barium Enema: a series of X-rays of the colon and rectum. Large polyps and cancers may be detected.
CT Colongraphy virtual colonoscopy): a procedure that uses CT images to produce pictures of the colon. A physician's computer with specialized software then assembles these pictures into a detailed three-dimensional movie that can show polyps and other abnormalities. Virtual colonoscopy may cause less discomfort and take less time than a traditional colonoscopy. If a polyp is found, it may be removed or a biopsy may be performed using traditional colonoscopy.
Fecal Occult Blood Test: a simple screening test to find unseen blood in the stool, which can be a sign of cancer in the colon or rectal area.
Biopsy: if a mass or any other abnormal areas are seen through the colonoscope or flexible sigmoidoscope, a sample will be taken. A pathologist examines the sample under the microscope to determine if cancer cells are present.
CT-Guided Needle Biopsy: a test performed if metastasis is suspected. For this test you lie on the CT scanning table while a radiologist places a biopsy needle in the suspected tumor. A fine needle biopsy sample (tiny fragment of tissue) is removed and examined under the microscope.