Colorectal cancer, cancer of the colon and rectum, is the second leading cause of cancer mortality in America. Colon cancer occurs in the large intestine.
If the cancer is in the last 6 inches of the colon (the rectum), it is considered rectal cancer. The colon is the lower part of the digestive system, which processes food for energy and rids the body of solid waste. Together, these cancers are referred to as colorectal cancers. Most of these cancers begin as benign adenomas, or polyps that grow on the inner lining of the colon or rectum. These growths spread very slowly, taking from 10 to 20 years to become cancerous. Regular screening tests can identify and remove polyps before they become cancerous. Once it is diagnosed, the prognosis depends on how much the cancer has spread.
Most cases of colorectal cancer occur in people over 50. Although it is responsible for thousands of deaths every year, it is highly treatable if caught early.
What are the Symptoms of Colorectal Cancer?
Unfortunately, most people with this cancer do not have any symptoms in the early stage of the disease. That is why screening tests, such as a colonoscopy, are so important.
In general, signs and symptoms can include the following:
- Changes in bowel habits
- Blood in the stool
- Problems related to blood loss (anemia, weakness, fatigue, shortness of breath, pounding or racing heart, chest pain, and intolerance to exercise)
- Abdominal discomfort (frequent gas, bloating, fullness, cramps, and pain)
- Unexplained weight loss
- Pain with bowel movement
- Feeling that your bowel does not empty completely
These symptoms may be caused by cancer or by other conditions such as infections, hemorrhoids, and inflammatory bowel disease. It is important to tell your doctor about any of these symptoms.
More than half of all colorectal cancers occur without any known cause. Studies also suggest that genetics may play a role. Some people who are diagnosed carry specific genetic mutations or have relatives with the condition. Those with a family history of specific genetic syndromes, such as familial adenomatous polyposis, Lynch syndrome, juvenile polyposis, and Peutz-Jeghers syndrome, are also at an increased risk of developing colorectal cancer. About 25% of people have a familial component. Smoking and eating a high-fat diet also raise the risk of developing cancer.
Risk factors include:
- Age (being over 50)
- Having colorectal cancer previously
- Having a history of adenomatous polyps
- Family history of colorectal cancer
- Eating a high-fat diet
- Prolonged consumption of red and processed meat
- Being overweight
- Heavy use of alcohol
- Having inflammatory bowel disease (such as Crohn disease and ulcerative colitis)
- Having diabetes
- Previous endometrial or ovarian cancer
- Women undergoing radiation for gynecologic cancer
You doctor will take a complete medical history, perform a physical exam, and may order one or more tests to diagnose colorectal cancer including sigmoidoscopy, colonoscopy, and barium enema. During a sigmoidoscopy or a colonoscopy, your doctor removes a sample of tissue (called a biopsy) from the colon or rectum and examines it under a microscope to detect abnormal growths. If cancer is evident, your doctor will perform a series of tests (chest x-ray, abdominal CT scan, and blood tests to check liver function) to see if the cancer has spread and to help determine the stage (or extent) of the disease.
Stages of Colorectal Cancer
- Stage 0: The earliest stage; cancer is found only in the innermost lining of the colon and/or rectum.
- Stage i: Cancer has grown through the innermost lining but hasn't spread beyond the colon wall or rectum.
- Stage ii: Cancer has spread to deeper layers of the wall of the colon or rectum, but not the lymph nodes.
- Stage iii: Cancer has spread to nearby lymph nodes but not to other parts of the body.
- Stage iv colorectal cancer: Cancer has spread to other parts of the body, such as the liver and lungs.