Colon Cancer

Description

Colon cancer is the second leading cause of cancer death in both sexes, accounting for about 10% of all cancer deaths. Colon cancer is the third most common cancer in both men and women, and is also the most hereditary of all cancers: about 10% of adults with colon cancer have a family history of the disease.

Colon cancer usually strikes after age 40.

Causes

According to the American Cancer Society, most colon cancers begin as a polyp (adenoma) or growth on the inside of the rectum and colon. Removing these adenomas early may prevent them from becoming cancerous.

Other key risk factors for colon cancer include having an inflammatory bowel disease (CrohnÕs disease or ulcerative colitis) or diabetes, or having a family member with colon cancer.

Unhealthy lifestyle factors, such as lack of exercise and obesity, also raise oneÕs risk for colon cancer, as does the typically Western diet rich in red and processed meats, sweets, and refined carbohydrates.

The main factors that can initiate colorectal cancer development are meat intake, altered vitamin and mineral intake, bile acids, fecal mutagens, fecal pH, and a predisposition to the effects of mutagen (such as heterocyclic amines, which are formed in cooked meats).

There is a link between hormones (estrogen and progesterone) and colon cancer risk. Women who take birth control pills for at least 5 years have a lower risk of colon cancer. The longer a woman takes the pill, the more she lowers her risk. Women who take post-menopausal hormones for at least 5 years have a lower risk of colon cancer.

Conventional Labs

Anemia, caused by GI bleeding, is often seen on routine blood tests.

Fecal occult blood test is a routine test conducted in a physicianÕs office that looks for blood in the stool. This test can be negative in those with colon cancer, as not all polyps bleed all the time.

Flexible-tube colonoscopy is the most invasive and accurate of colon cancer screening tests. It requires laxative-induced preparation of the colon the day before the procedure and may require sedation during it. The American College of Gastroenterology now considers this form of colonoscopy to be the ÒpreferredÓ screening test.

Sigmoidoscopy requires no sedation, but examines only the lower third of the colon, where most cancers occur. Polyps are biopsied, and adenomatous or cancerous polyps are removed by sigmoidoscopy or flexible-tube colonoscopy.The risk of missing cancer in the upper two thirds of the colon makes sigmoidoscopy only partially effective and therefore not highly recommended.



Barium enema requires no sedation, but if polyps are found, a flexible-tube colonoscopy is necessary for treatment. The test should be repeated every five years. This procedure exposes the lower abdominal cavity to radiation that may be associated with increased risk of cancers, and thus is not recommended.



Virtual colonoscopy is a 15-minute, computer-enhanced screening test (also called CT colonography) that does not require sedation and uses a computerized technology scanner to provide three-dimensional images of the entire colon. A flexible-tube colonoscopy is required to remove any polyps found. High-dose radiation exposure, the inability to remove polyps found, and a lower detection rate of polyps and cancerous lesions makes virtual colonoscopy less desirable than flexible-tube colonoscopy.



CEA is usually elevated with bulky tumors or metastases.

Urinary 5-HIAA Is elevated in carcinoid.



Elevated C-reactive protein (CRP), a marker for inflammation and cardiovascular disease, may also be a risk factor for colon cancer, according to a study published in the February 4 2004 issue of The Journal of the American Medical Association (JAMA).

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