Colon cancer is cancer of the large intestine (colon), which is the lower part of the digestive system. Rectal cancer occurs on the last eight to 10 inches of the colon. They are often referred to together as colorectal cancers, and are the second leading cause of cancer-related deaths in the United States.
The rectum is part of the body's digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the esophagus, stomach, and the small and large intestines. The first six feet of the large intestine are called the large bowel or colon. The last six inches are the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).
The incidence of colorectal cancer is slightly higher in men than women, and is highest in African American men. The incidence of colorectal cancer is highest in developed countries such as the United States and Japan, and lowest in developing countries such as Africa and Asia. This is in part due to dietary differences, such as consumption of more red meats in developed countries.
The estimated number of new cases and deaths from colon and rectal cancer in the United States in 2007 are as follows: new cases: 112,340 (colon); 41,420 (rectal); deaths: 52,180 (colon and rectal combined).
Ashkenazi Jewish individuals have a higher incidence of a specific genetic mutation (called I1307K) that increases the risk for colorectal cancer.
Of the 150,000 cases of colorectal cancer diagnosed each year in the United States, more than 40,000 people are diagnosed with rectal cancer.
The American Cancer Society (ACS) states that most (over 95%) colorectal cancers are adenocarcinomas (cancer in the glands or secretory cells) that develop when a change occurs in cells that line the wall of the colon or rectum. The disease often begins as an intestinal polyp, also called an adenoma, which is an abnormal growth of tissue. Polyps can gradually become precancerous and then cancerous.
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