Almost all cases of colorectal cancer, also referred to as colon cancer, begin with the development of benign colonic polyps. Polyps form when cells lining the colon grow, divide and reproduce in an unhealthy, disorderly way, producing a growth. These polyps can be cancerous, invading the colon wall and surrounding blood vessels, and spreading to other parts of the body.
Colorectal cancer frequently begins without symptoms. The exact causes of colorectal cancer are unknown, but the disease appears to be caused by both inherited and lifestyle factors. Diets high in fat and low in fruits and vegetables – such as those that include red meat, fried foods and high-fat dairy products – may increase the risk of colorectal cancer. Lifestyle factors –such as cigarette smoking, a sedentary lifestyle, and obesity – also may increase the risk of developing the disease. Genetic factors may determine a person's susceptibility to the disease, whereas dietary and other lifestyle factors may determine which at-risk individuals actually go on to develop the disease.
Colorectal cancer is the second leading cancer killer in the United States, and the third most common cancer overall. This year, more than 50,000 Americans will die from colorectal cancer and approximately 131,600 new cases will be diagnosed. Eighty to 90 million Americans (approximately 25 percent of the US population) are considered at risk because of age or other factors. More women over the age of 75 die from colorectal cancer than from breast cancer.