Colorectal Cancer Health Article

Definition

Colorectal cancer is a malignancy of the colon (bowel) and/or rectum. It is the second most common cause of cancer-related death in the United States, and is diagnosed in more than 130,000 new patients annually.

Description

Colorectal cancer occurs in either the last 6 ft (1.8 m) of intestine, known as the large bowel or colon, and/or in the rectum, where the colon terminates and waste (feces) leaves the body. The majority of malignancies that occur in colorectal cancers are called adenocarcinomas. When an individual develops colorectal adenocarcinomas, malignant cancer cells grow inside the colon and/or the rectum. Large clusters of these cells form structures known as tumors.

Causes & risk factors

The exact cause of colorectal cancer is unknown. However, there are a number of known risk factors that increase the odds for developing the disease. They include:

• Family history. Individuals who have one or more close relatives that were diagnosed with colorectal cancer may be at increased risk for the disease. In 2003, research showed that about 5% of colorectal cancer patients had inherited syndromes.
• History of bowel disease and/or colon polyps. Certain types of colon polyps, which are tumor-like, benign outgrowths of tissue within the colon, may act as an early warning sign of or a precursor to colorectal cancer. They may develop into malignancies later in life. Colon diseases that cause inflammation and irritation of the bowel, such as Crohn's disease and inflammatory bowel disease, also can increase an individual's risk of developing a colorectal malignancy.
• Obesity. Overweight individuals, especially those with an apple-shaped body type (where fat is concentrated around the waist) as opposed to a pear-shaped body (where fat is stored in the hips and thighs), are at an increased risk for colorectal cancer. A high fat diet also increases an individual's chance of developing colorectal cancer.
• Age. Individuals over age 50 are at an increased risk for colorectal cancer.
• Sedentary lifestyle. A moderate exercise program is thought to have a preventive effect against cancer.
• Night work. A 2003 study showed that working the night shift actually may increase risk of colorectal cancer in women. Exposure to light at night suppresses the body's natural production of melatonin, a hormone that helps keep certain intestinal cancers from proliferating.