Colon cancer occurs when the cells in the colon or rectum grow and multiply uncontrollably, damaging surrounding tissue and interfering with the normal function of the colon or rectum. Colon cancer is the third most common cancer diagnosed in the United States. Most colon cancers (about 70 percent) are found in the first six feet of the large intestine. The other 30 percent occur in the last 10 inches of the large intestine (rectum). Collectively they are referred to as colorectal cancers.
One in 19 Americans will be diagnosed with colon cancer in their lifetime, for an overall risk of 5.4 percent. Although colon cancer affects men and women equally, rectal cancer is more common in men. When colon and rectal cancers are found early, there is nearly a 90 percent chance for cure. About 80 percent of colon cancer cases are sporadic, meaning that cause is nonspecific or undetermined. The other 20 percent of colon cancers are hereditary. People who have a first-degree family member with colon cancer are more likely to be affected themselves. About 5 percent of this group has a predisposition to hereditary non-polyposis colorectal cancer (Lynch syndrome), a rare disease that generally strikes people aged 30 to 50.
There often are no symptoms of colon cancer in its early stages. Most colon cancers begin as a polyp, a small non-cancerous growth on the colon wall that can grow larger and become cancerous. As polyps grow, they can bleed or obstruct the intestine.
- Rectal bleeding
- Blood in the stool or toilet after a bowel movement
- Prolonged diarrhea
- A change in size or shape of your stool
- Abdominal pain or a cramping pain in your lower stomach
- A feeling of discomfort or urge to have a bowel movement when there is no need
Many colon symptoms are not cancer, but if you notice one or more of these symptoms for more than two weeks, see your doctor.