July 29, 2016
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Colon Cancer Screening and Surveillance

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Introduction to colon cancer screening and surveillance

The colon, also known as the large intestine or large bowel, constitutes the last part of the digestive tract. The colon is a long, muscular tube that receives still-undigested food from the small intestine. It removes water from the undigested food, stores it and then finally eliminates it from the body as stool or feces through bowel movements. The rectum is the last part of the colon adjacent to the anus through which stool passes to the outside.

Cancer of the colon and rectum (colorectal cancer) is a type of malignant tumor arising from the inner wall of the large intestine. These malignant tumors are called cancers and can invade nearby tissue and spread to other parts of the body. Benign tumors of the colon are usually called polyps. Benign polyps do not invade nearby tissue or spread to other parts of the body like malignant tumors do. Benign polyps can be removed easily during colonoscopy and are not life threatening. However, if benign polyps are not removed from the large intestine, they can become malignant over time. In fact, most of the cancers of the large intestine are believed to have evolved from benign polyps that are pre-cancerous, that is, they are benign at first but later become cancerous.

Colorectal cancer will be found in at nearly 135,00 patients this year and will result in about 50,000 deaths in the U.S. It is the second most common cause of cancer death in the USA behind lung cancer. It is the third most common cancer in both men and women.

Cancer of the colon and rectum can invade and damage adjacent tissues and organs. Cancer cells also can break away and spread to other parts of the body (such as the liver and lung) where new tumors grow. The process whereby colon cancer spreads to distant organs is called metastasis, and the new tumors are called metastases. Direct extention to or invasion of adjacent organs is a sign of a more advanced cancer, and the chance of cure in the treatment of a cancer which has directly extended into an adjacent tissue is less, even with surgery, as hidden cancer cells may also have spread elsewhere. If a colon or rectal cancer is found to have spread through the lymph channels to adjacent lymph nodes, it is increasingly likely that even the removal of the portion of the colon and lymph nodes will not cure the patient. Finding lymph node metastases can indicate that undetectable microscopic cancer cells may be more likely to still be present elsewhere in the body. If the cancer spreads through the blood stream to the liver, lungs, bones, or other organs, or through lymph channels to distant lymph nodes then it is unlikely that a permanent complete cure will be able to be obtained with treatment.

Colorectal cancer is both preventable and curable when found early. Colorectal cancer is prevented by removing precancerous colon polyps. It is cured if cancerous change is found early and is surgically removed before the cancer cells spread to other parts of the body. The National Polyp Study showed in its surveillance program that individuals who had their polyps removed experienced a 90% reduction in the incidence of colorectal cancer. The few patients in the study who did develop colorectal cancer had their cancer discovered at early, surgically or endoscopically curable stages. Since most colon polyps and early cancers are silent (produce no symptoms), it is important to do screening and surveillance for colon cancer in patients without symptoms or signs of the polyps or cancers. Recommendations for cost-effective public screening and surveillance have been promulgated and endorsed by numerous societies including the American Cancer Society, the National Cancer Institute, American College of Gastroenterology, American Medical Association, American College of Physicians, etc.

Medically Reviewed by a Doctor on 2/23/2016

Source: MedicineNet.com


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