Colorectal cancer refers to the uncontrolled growth of abnormal cells in the colon or rectum, which are part of the digestive system. This cancer usually begins as polyps, which are abnormal growths in the inner lining of the colon or rectum. Polyps are not cancer but can become cancerous over the years. More than 95 percent of colorectal cancer is adenocarcinoma, which is cancer of the gland cells that line the inside wall of the large intestine.

Some risk factors for colorectal cancer cannot be controlled, such as having a family history of this cancer, age and ethnicity. A person with a history of chronic inflammatory bowel disease also has a higher risk for developing colorectal cancer.

However, some lifestyle habits can increase the risk of this cancer. A diet high in animal fat and low in fiber, physical inactivity and smoking are some of the lifestyle habits that increase the risk for colorectal cancer.

Screening for colorectal cancer is important because symptoms of the disease may be absent or may be related to other conditions. Possible indicators include changes in bowel habits, abdominal pain and bleeding from the rectum.

Diagnostic tests for colorectal cancer include tests for blood in the stool, a special type of enema x-ray, flexible sigmoidoscopy and colonoscopy. Ultrasound, blood tests, x-rays and magnetic resonance imaging (MRI) also may be used to help diagnose the condition. 

The most common treatment for colorectal cancer is surgery. Patients may also receive radiation therapy or chemotherapy before or after surgery, or instead of surgery if surgery is not feasible. In many cases, patients may receive a combination of these therapies. A patient’s cancer care team, which is typically headed by a medical oncologist, is responsible for the planning and implementation of the treatment plan.

The American Cancer Society (ACS) estimates that in 2007 there will be more than 112,000 new cases of colon cancer and nearly 42,000 of rectal cancer in the United States. Together, these cancers will cause about 53,000 deaths in 2007.

Colorectal cancer is the number two cause of cancer-related deaths in the United States, surpassed only by lung cancer. However, the mortality rate from this disease has declined over the past 15 years. This decrease may be attributed to a higher number of polyps being found by screenings when they are precancerous. Also, colorectal cancer is being detected and treated in earlier stages when the disease is more likely to be cured. The ACS estimates that there are more than 1 million colorectal cancer survivors in the United States today.