What screening tests are used to detect colorectal cancer?
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American Cancer Society answered:If symptoms or the results of the physical exam or blood tests suggest that colorectal cancer might be present, your doctor may recommend more tests. This might include endoscopic tests such as sigmoidoscopy or colonoscopy, or imaging tests such as a barium enema (lower GI series).
Biopsy: Usually if a suspected colorectal cancer is found by any diagnostic test, it is biopsied during a colonoscopy. In a biopsy, the doctor removes a small piece of tissue with a special instrument passed through the scope. There may be some bleeding afterward, but this usually stops after a short time. Less often, part of the colon may need to be surgically removed to make the diagnosis.
Lab tests of samples: Biopsy samples (from colonoscopy or surgery) are sent to the lab where a pathologist, a doctor trained to diagnose cancer and other diseases in tissue samples, looks at them under a microscope. Other tests may suggest that colorectal cancer is present, but the only way to determine this for certain is to look at the samples under a microscope.
Other lab tests may also be done on biopsy specimens to help better classify the cancer. Doctors may look for specific gene changes in the cancer cells that might affect how the cancer is best treated. For example, doctors now typically test the cells for changes in the K-ras gene. This gene is mutated in about 4 out of 10 colorectal cancers. Some doctors may also test for changes in the BRAF gene. Cancers with mutations in either of these genes do not benefit from treatment with certain anti-cancer drugs such as cetuximab (Erbitux) and panitumumab (Vectibix).
If symptoms or the results of the physical exam or blood tests suggest that colorectal cancer might be present, your doctor may recommend more tests. This might include endoscopic tests such as sigmoidoscopy or colonoscopy, or imaging tests such as... More -
Dr. Mehmet Oz answered:There are alternatives to colonoscopy but they are less likely to prevent cancer compared with the invasive tests: guaiac-based fecal occult blood testing (gFOBT), fecal immunochemical testing (FIT) and stool DNA testing (sDNA), barium enema and computed tomography (CT) colonography. Still, most doctors will recommend colonoscopy to screen for colorectal cancer. [A sigmoidoscopy is a similar tool but only visualizes the first third of the colon.]There are alternatives to colonoscopy but they are less likely to prevent cancer compared with the invasive tests: guaiac-based fecal occult blood testing (gFOBT), fecal immunochemical testing (FIT) and stool DNA testing (sDNA), barium enema and... More -
Dr. Darren Pollock of Swedish answered:There are several screening tests for colorectal cancer. One option is for your doctor to examine your bowel movement for minute traces of blood. However, this test is largely inaccurate, missing 50 percent of cancers and 90 percent of polyps.
Another option is flexible sigmoidoscopy, which uses a flexible instrument to look at the colon. This test is also unreliable because it looks only at the lower third of the colon and therefore will miss polyps in other areas. The "gold standard" test is called a colonoscopy. This procedure entails inserting a flexible, camera-like instrument into the body to look at the inside of the colon and large intestine. This instrument also has the potential to remove any polyps to prevent colorectal cancer from forming.
There are several screening tests for colorectal cancer. One option is for your doctor to examine your bowel movement for minute traces of blood. However, this test is largely inaccurate, missing 50 percent of cancers and 90 percent of polyps.... More -
Several tests are available to screen for colorectal cancer. Some are used alone; others are used in combination with each other. Talk with your doctor about which test or tests are best for you. The U.S. Preventive Services Task Force recommends these tests:
- Colonoscopy (every 10 years).
- High-sensitivity fecal occult blood test (FOBT), also known as a stool test (every year).
- Flexible sigmoidoscopy (every 5 years) with high-sensitivity FOBT (every 3 years).
Several tests are available to screen for colorectal cancer. Some are used alone; others are used in combination with each other. Talk with your doctor about which test or tests are best for you. The U.S. Preventive Services Task Force... More -
UCLA Health answered:The following screening tests can be used to detect polyps, cancer, or other abnormal areas. Your doctor can explain more about each test:
Fecal occult blood test (FOBT): Sometimes cancers or polyps bleed, and the FOBT can detect tiny amounts of blood in your stool. If this test detects blood, other tests are needed to find the source of the blood. Benign conditions (such as hemorrhoids) also can cause blood in your stool. Sigmoidoscopy: Your doctor checks inside your rectum and the lower part of the colon with a lighted tube called a sigmoidoscope. If polyps are found, your doctor removes them. The procedure to remove polyps is called a polypectomy. Colonoscopy: Your doctor examines inside the rectum and entire colon using a long, lighted tube called a colonoscope. Your doctor removes polyps that may be found. Double-contrast barium enema: You are given an enema with a barium solution, and air is pumped into your rectum. Several x-ray pictures are taken of your colon and rectum. The barium and air help your colon and rectum show up on the pictures. Polyps or tumors may show up. Digital rectal exam: A rectal exam is often part of a routine physical examination. Your doctor inserts a lubricated, gloved finger into your rectum to feel for abnormal areas. Virtual colonoscopy: This method is under study.
This answer is based on source information from National Cancer Institute.The following screening tests can be used to detect polyps, cancer, or other abnormal areas. Your doctor can explain more about each test: Fecal occult blood test (FOBT): Sometimes cancers or polyps bleed, and the FOBT can detect tiny amounts of... More -
Dr. Daniel Labow of The Mount Sinai Medical Center answered:The most important screening test for colon cancer is a colonoscopy. Other tests can be done that could indicate colon or rectal cancer, but a full colonoscopy is the gold standard. If you cannot tolerate a colonoscopy, Barium enema or “Virtual” colonoscopy can be done, but these tests are less specific and if a biopsy is needed, then the colonoscopy needs to be performed anyway. In an average risk patient, first colonoscopy should be done at age 50, if the patient doesn’t have any symptoms. Any symptoms such as bleeding, change in bowel habits, unexplained weight loss, etc., should prompt a visit to your doctor for evaluation.
The most important screening test for colon cancer is a colonoscopy. Other tests can be done that could indicate colon or rectal cancer, but a full colonoscopy is the gold standard. If you cannot tolerate a colonoscopy, Barium enema or... More -
Tests for screening for colorectal cancer are the following: fecal occult blood, flexible sigmoidoscopy, colonoscopy, barium enema, virtual barium enema colonoscopy. Each of these will need to be followed by a biopsy to definitively diagnose the lesion as cancer.Tests for screening for colorectal cancer are the following: fecal occult blood, flexible sigmoidoscopy, colonoscopy, barium enema, virtual barium enema colonoscopy. Each of these will need to be followed by a biopsy to definitively diagnose the... More
