Sylvester Comprehensive Cancer Center

Education: Colorectal Cancer

Internal Organs

Colorectal cancer is the third most common cancer (excluding skin cancer) among American men and women. According to the American Cancer Society, more than 100,000 new cases of colon cancer and 40,000 new cases of rectal cancer are diagnosed annually in the U.S. These cancers are highly curable when detected and treated early.

To understand colorectal cancer and how it spreads, it is helpful to understand a little about the anatomy of the colon and the rectum. The colon and the rectum are part of the large intestine, which is part of the digestive system. The digestive system removes nutrients from food and stores waste until it passes out of the body. Tumors—abnormal cells that divide uncontrollably and form a mass—can be found in either the colon or rectum. These tumors can be malignant (cancerous) or benign (non-cancerous).

More than 95 percent of colorectal cancers are adenocarcinomas (cancers of the glandular cells that line the inside of the colon and rectum). The treatment and prognosis for other rarer types of colorectal tumors is different from that for adenocarcinomas. The information contained in this site deals primarily with adenocarcinomas.

The colon, or large bowel, includes the first six feet of the large intestine, and the rectum includes the last six inches. Because colon cancer and rectal cancers have many features in common, they are sometimes referred to together as colorectal cancer. Cancerous tumors found in the colon or rectum may spread to other parts of the body.
Risk Factors

While the exact cause of colorectal cancer is unknown, certain risk factors for the disease have been identified. A risk factor is anything that may increase a person’s chance of developing a disease.

Although these factors can increase a person’s risk, they do not necessarily cause the disease. The risk factors for colorectal cancer include:

  • Age 50 or older
  • Polyps, which are non-cancerous growths on the wall of the colon or rectum
  • A personal history of colorectal, ovarian, uterine, or breast cancer
  • A family history of colorectal cancer or polyps
  • Diseases that cause inflammation in the lining of the intestine such
  • as ulcerative colitis or Crohn’s disease
  • Obesity
  • Physical inactivity
  • A high-fat and/or low-fiber diet
  • Alcohol abuse
  • Smoking

These factors do not necessarily cause colorectal cancer; however, they increase a person’s risk for developing the disease. Changing risk factors that can be controlled, such as smoking and physical inactivity, may decrease a person’s risk for colorectal cancer.