Colon Cancer

Colon Cancer

Only lung cancer kills more Americans than colorectal cancer. Fear, denial and embarrassment keep many people from being screened for the disease. There is also a misperception that colon cancer mainly strikes men. Yet colorectal cancer is the third most common malignancy in women after breast and lung cancer. Men and women develop colorectal cancer with almost equal frequency. In fact, more women over 75 die of colorectal cancer than of breast cancer.

There are regional differences in the disease's incidence and mortality throughout the country with the highest rates occurring among those in the Northeast, and survival rates lowest among African Americans.

The good news is that the disease is not only highly beatable and treatable, but also highly preventable. Screening for colon cancer can reduce deaths from colon cancer by at least 60 percent by preventing its development in the first place.

About 90 percent of those diagnosed with colon cancer survive five years or longer if the disease is diagnosed at an early stage. Once the cancer has spread to the lymph nodes, however, the five-year survival rate drops to 67 percent. If the cancer has already spread to distant parts of the body such as the liver or lungs, the five-year survival rate goes down to 10 percent.

The large intestine is the last section of the digestive tract and consists of the colon and rectum. The colon is four to six feet long, the last 12 to 15 centimeters or seven to nine inches of which is called the rectum. After food is digested in the stomach and nutrients are absorbed in the small intestine, waste from this process move into the colon, where it solidifies and remains for one or two days until it passes out of the body.

Sometimes the body produces too much tissue, ultimately forming a tumor. These tumors can be benign (not cancerous) or malignant (cancerous). In the large intestine, these tumors are called polyps. Polyps are found in about 30-50 percent of adults.

There are several different types of polyps. Inflammatory polyps, hyperplastic polyps and lymphoid polyps don't typically develop into colorectal cancer. However, researchers find that polyps called "adenomas" may undergo cancerous changes, becoming adenocarcinomas. Overall, about one percent of adenomatous polyps less than one cm in size will undergo this change, 10 percent of adenomatous polyps greater than one cm will become malignant within 10 years and 25 percent of adenomas greater than one cm will become malignant within 20 years. Furthermore, people with polyps in their colon tend to continue to produce new polyps even after existing polyps are removed.

The important fact is that colon cancers develop from adenomatous polyps by growing larger and eventually transforming into cancer; it is believed to take about 5 to 10 years for an adenomatous polyp to grow into cancer. Therefore, if appropriate colorectal cancer screening is performed, most of these polyps can be removed before they turn into cancer, effectively preventing the development of colon cancer.

Besides adenocarcinomas, there are other rare types of cancers of the large intestine, including carcinoid tumors typically found in the appendix and rectum; gastrointestinal stromal tumors found in the connective tissue of the colonic or rectal wall; and lymphomas, which are malignancies of immune cells that can involve the colon, rectum and lymph nodes.