GastroEast Physicians, Louisville, KY

Colorectal Cancer (CRC) Screening

Screening for colorectal cancer has prevented countless deaths from colon cancer in this country and abroad. About 30% of people doctor using scope who develop colon cancer die from this disease, so preventing colon cancer by removing the precursor to colorectal cancer, the precancerous polyp, is quite important. In fact, colorectal cancer screening via colonoscopy is the only screening test in this country widely used to prevent cancer before it develops. All other screening tests in this country detect cancer at its various stages; but unfortunately, they detect it after cancer has developed. Colorectal cancer screening via colonoscopy detects and removes the pre-cancerous lesion, the adenomatous colon polyp.

There is a general consensus that colorectal cancer screening should begin in normal risk patients at age 50, 45 for African-Americans. Colon cancer usually takes between 7-10 years to develop from a pre-cancerous or adenomatous polyp. The goal is to find these polyps and remove them before they progress to cancer and become incurable.
Screening for and removal of adenomatous polyps reduces a person's risk of developing colon cancer by up to 80-90 percent.

While average-risk screening should begin between 45 and 50, high-risk individuals need screening at an earlier age.

Increased risk individuals will need colonoscopy at more frequent intervals as follows:

1) A patient with a history of previous adenomatous polyps or colorectal cancer. These individuals will need colonoscopy within 1-5 years after their polyps/cancer was diagnosed. They will also need colonoscopy at regular (usually five year), intervals for the rest of their lives.

2) A patient who has an immediate family member (sibling, parent or child) with colon cancer will need more frequent colonoscopy and usually at an earlier age than a normal-risk individual. Screening with colonoscopy usually begins at age 40 or ten years younger than the earliest diagnosis in their family. In other words, if a patient has a parent who was diagnosed with colon cancer at age 45, screening for the immediate family members should begin at age 35.
People with a second-degree relative or third-degree relative with colon cancer should be screened as average-risk patients are screened, it has not been proven that anyone with a second or third degree relative with colon cancer has an increased risk of developing it themselves.

3) A patient with Crohn’s disease or Ulcerative Colitis will need more frequent colonoscopy then an average-risk individual.

4) Patients with certain inherited conditions which have a predilection to develop colon cancer will need screening with colonoscopy at an early age, usually puberty. These diseases, FAP or familial adenomatous polyposis, and HNPCC or hereditary nonpolyposis colon cancer, have nearly a 100% chance of developing colon cancer during a patient's lifetime; therefore surgical removal of the colon in these individuals is now universally accepted.

The following tests have been approved for screening for colorectal cancer but are used less frequently than colonoscopy. These tests are used less frequently because only colonoscopy can visualize the entire large intestine and remove polyps in the same session.

1) Fecal occult blood testing;
2) Flexible sigmoidoscopy
3) Barium enema

The fecal occult blood test, when performed once every year, may decrease the risk of dying from colorectal cancer by 30%. This test is the least sensitive screening test because polyps bleed only periodically, but it is least invasive, requiring sampling of stool and placing stool onspecial cards that detect blood. digestive tract

Sigmoidoscopy allows direct viewing of the lining of the bottom 1/3 of the colon. Because a patient with polyps in the upper 2/3 of the colon has an increased chance of having polyps in the lower 1/3, if polyps are seen on flexible sigmoidoscopy, a full colonoscopy is then performed to visualize the entire colon.

If sigmoidoscopy is normal, it is repeated every five years to rule out polyp formation. Complication rate is low, and discomfort is minimal. The major drawback is that a polyp may exist in the upper colon, whereas one does not exist in the lower colon. If this occurs, the polyp in the upper colon will never be found and will grow unchecked and rarely may develop into colon cancer.

A barium enema test provides a detailed x-ray picture of the rectum and the entire colon. Doctors usually recommend a specific type of test called a double-contrast barium enema, which not only instills barium but also air in the colon. The advantage of this test is that it examines the whole colon; the drawback is that stool within the colon may obscure views and polyps may be missed. Even when stool is not present, small polyps may be missed because this test is not directly visualizing the inside of the colon. Occasionally, a doctor will order a Barium enema and a flexible sigmoidoscopy together to screen for colon cancer.If a barium enema test reveals an abnormality, the doctor may recommend colonoscopy to examine the whole colon with direct visualization.

Colonoscopy
Colonoscopy is the only screening test we have that directly visualizes the lining of the entire colon. This test not only allows visualization of polyps, but also allows the doctor to remove polyps in their entirety, thus preventing their progression to colon cancer. Only a very small proportion of polyps go on to form colon cancer, but all polyps are removed and examined under the microscope in order to see if they are pre-cancerous. If they are pre-cancerous, more frequent colonoscopy will be necessary in the future usually between 3-5 years later. While colonoscopy is the best test to locate and remove polyps it carries more risk than any of the other screening tests. Complications such as a tear in the colonic lining (1/2000 procedures) or bleeding from polyp removal (1/1000) can occur and can cause hospitalization, surgical repair, or even death. Death is extremely rare and most always occurs in patients who are already gravely ill, wherein colonoscopy is performed to try to save their lives -- for example, a patient who is bleeding to death from diverticular hemorrhage.

Doctors recommend that individuals with an average risk of CRC begin screening at 50 years of age, 45 for AfricanAmericans. No screening test listed above has been proven to be the best as of yet. Therefore, all screening testsshould be discussed with your doctor to choose the right test for you. Keep in mind, though, colonoscopy is the screening method used by over 90% of all physicians in this country and is endorsed by the American College of Gastroenterology as the most accurate and complete screening test for colon cancer available. Also keep in mind that if fecal occult blood testing, flexible sigmoidoscopy, or barium enema yield a significant result or positive finding, a colonoscopy will be needed in order to visualize the entire lining of the colon and remove polyps if found.

CT colonography or virtual colonoscopy
CT(CAT scan) colonography or virtual colonoscopy is not endorsed by the American College of Gastroenterology as appropriate for widespread screening for colon cancer. CT colonography requires full bowel preparation with laxatives similar to regular colonoscopy; but unlike regular colonoscopy, virtual colonoscopy occurs while the patient is awake; and CT colonography can be painful. This x-ray test has been shown to miss polyps and does not allow for removal of the pre-cancerous polyp. If a polyp is seen on the CAT scan, however, a regular colonoscopy will still need to be performed to remove the polyp. This would require another full bowel preparation on another day.

By contrast, regular colonoscopy is done with the patient under sedation. Greater than 95% of all patients who undergo regular colonoscopy have no pain or discomfort, and 80% have no recollection of even having had the procedure.