Colon Cancer Screening And Surveillance

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 undigested food from the small intestine. It removes water from the undigested food, stores it and then finally eliminates it from the body through bowel movements. The rectum is the last part of the colon adjacent to the anus.

Cancer of the colon and rectum (colorectal cancer) is a malignant tumor arising from the inner wall of the large intestine. These malignant tumors invade nearby tissue and spread to other parts of the body. Benign tumors of the colon are 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 (cancerous) 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.

Cancer of the colon and rectum invades and damages 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 sprocess whereby colon cancer preads to distant organs is called metastasis, and the new tumors are called metastases. Once metastasis has occurred in colorectal cancer, a complete cure of the cancer is unlikely.

Colorectal cancer is both preventable and curable. Colorectal cancer is prevented by removing precancerous colon polyps . It is cured if it is found early and is surgically removed before it spreads 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.