Colon cancer can be either hereditary, or it can result from an accumulation of genetic defects that accumulate in an individual's lifetime. The epithelial cells that line the interior of the colon are very active, constantly dividing and renewing themselves. During the process, they create small buds called polyps that protrude into the colon. The vast majority of these polyps remain benign and never develop into cancer. A small number of these polyps could continue to grow, and through the accumulation of genetic changes develop into cancer. This type of cancer is known as adenomatous, since it originates from epithelial tissue and is glandular in appearance. Another type of tumor known as lateral spreading or flat and depressed occurs in a small number of cases. This non-polyp type of tumor is more easily missed in screening.
Traditional screening methods
1. Fecal Occult Blood Test - The appearance of blood in the stool is one of the warning signs of colon cancer. However, the amount of blood present may be too small to be visible, hence the name. This is the simplest test, and costs only around $20. In order to achieve a sensitivity of 24% or more, six stool samples taken at different times must be tested. One of the problems is that not all cancerous polyps secrete blood, or only do so sporadically.
2. Colonoscopy - This is considered the gold standard for colon cancer screening, since it can have a detection rate of 98%. However, the procedure is expensive (around $2000 a procedure), and is inconvenient for the patient. The patient must first undergo a "prep" to clean out the colon. This prep involves drinking a phospho-soda solution. The fecal contents are then liquefied and evacuated. At the time of the procedure, the patient is given a mild sedative, and his or her colon is inflated. The physician inserts a colonoscope in the rectum, which is a thin flexible tube with a fiber optic light at the end. The colonoscope must be threaded through all the twists and turns of the colon. The colon consists of ascending, transverse, and descending sections. If the physician discovers polyps, they can be removed during the time of the procedure.
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