CancerSmart Web Cast Our experts -- Drs. Winawer, Saltz, and Weiser -- discuss the latest advances in the screening, diagnosis, and treatment of colorectal cancer 
|
|
|
Colorectal cancer is cancer that occurs in the large intestine and rectum. The colon is a muscular tube that is about five feet long. It absorbs water and nutrients from food. The rectum, the lower six inches of the digestive tract, serves as a holding place for stool, which then passes out of the body through the anus.
This year, about 148,000 people in the United States will be diagnosed with colorectal cancer. Although many people think of colorectal cancer as a disease that primarily affects men, it is slightly more common in women. Today, the average person has about a 1 in 20 chance of developing colorectal cancer during his or her life.
How Colorectal Cancer Develops
The colon is divided into four sections: the ascending colon, transverse colon, descending colon, and sigmoid colon. Most colorectal cancers arise in the sigmoid colon -- the portion just above the rectum. They usually start in the innermost layer and can grow through some or all of the several tissue layers that make up the colon and rectum. The extent to which a cancer penetrates the various tissue layers determines the stage of the disease. Most colorectal cancers grow slowly over a period of several years, often beginning as small benign growths called polyps. Removing these polyps early, before they become malignant, is an effective means of preventing colorectal cancer.
Types of Colorectal Cancer
More than 95 percent of colorectal cancers are adenocarcinomas -- cancers of the cells that line the interior of the colon and rectum. Rarer types of tumors include carcinoid tumors, gastrointestinal stromal tumors, and lymphomas. These latter types are reviewed elsewhere.
