Colon Cancer - Spotlight on Colon Cancer
Colorectal cancer refers to any of several cancers that develop in a person’s colon or rectum. The colon and rectum are parts of the human digestive, or gastrointestinal, system.
The digestive system is responsible for removing important nutrients from the food we eat and then removing waste from the body. Swallowed food is broken down in the stomach and then moves on to the small intestine. The small intestine continues breaking down the food and absorbs most of the nutrients we ingest. The remainder passes on to the large intestine, or colon. The colon absorbs water and nutrients from the partially digested food and stores waste. This waste, known as feces or stool, then moves to the rectum, which is the last section of the digestive system, where the feces is eliminated from the body through the anus.
Both men and women can develop colorectal cancer. The American Cancer Society estimates that about 106,680 new cases of colon cancer (49,220 in men and 57,460 women) and 41,930 new cases of rectal cancer (23,580 men and 18,350 women) will be diagnosed in 2006.
The exact cause of most colorectal cancers is not yet known. However, research has shown the majority of colorectal cancers occur in people with no known risk factors. However, a person’s diet may contribute to colorectal cancer risk. People who eat foods high in fat, protein, and calories may increase their risk of developing colorectal cancer. There is also some evidence that smoking and drinking alcohol may increase the risk for developing colorectal cancer.
In most people, colorectal cancer develops slowly over a period of several years. Colorectal cancer generally develops from abnormal growths, called polyps, on the lining of the colon or rectum. Polyps and colorectal cancer do not always cause symptoms, especially at first. But sometimes there are symptoms, such as:
Unexplained and frequent pain, aches or cramps in your stomach
A change in bowel habits, such as having stools that are narrower than usual
Unexplained weight loss
Chronic fatigue
If you have any of these symptoms, discuss them with your doctor. Only your doctor can determine why you’re having these symptoms.
Screening
Certain medical tests can find polyps so they can be removed before they grow into cancer. Screening tests can also identify colorectal cancer early, when it is most treatable. When colorectal cancer is found early and treated, the 5-year relative survival rate is 90%. (The 5-year relative survival rate is the percentage of people alive at least five years after diagnosis of cancer.)
Several tests can be used alone or in combination to screen for colorectal cancer:
Flexible Sigmoidoscopy - In this exam, a flexible, lighted tube is used to examine the inside of the rectum and the lower colon. During the exam, the doctor may remove polyps and collect samples of tissue or cells for further examination.
Colonoscopy - This exam is similar to sigmoidoscopy except that a colonscopy examines the entire colon. This is the best and most thorough examination for polyps and cancer.
Double-Contrast Barium Enema - In this exam, a liquid called barium is inserted into the rectum and colon through the anus, followed by an injection of air. An X-ray of the rectum and colon is then taken. The barium coats the lining of the intestines so that polyps and other problem areas are visible on the X-ray.
Digital rectal exam - In this exam, the doctor inserts a lubricated, gloved finger into the rectum to feel for abnormal areas.
Colonoscopy is the most specific examination to diagnose polyps or cancer, but requires thorough cleansing of the colon and rectum and mild sedation during the exam. You should begin screening for colorectal cancer when you turn 50, then continue getting screened at regular periods. However, you may need to be tested earlier or more often than other people if you have:
Inflammatory bowel disease (ulcerative colitis or Crohn’s disease)
Genetic disorders such as familial adenomatous polyposis (FAP) or hereditary nonpolyposis colon cancer (HNPCC)
The death rate from colorectal cancer has been dropping for the past 20 years. One reason may be because polyps are being found by screening before they can develop into cancers. Also, colorectal cancer is being found earlier when it is easier to cure, and treatments have improved. Because of this, there are around 1 million survivors of colorectal cancer in the United States.
Treatment
The choice of treatment depends on the size, location, and stage of the cancer and on the patient’s general health. The three standard treatments for colon cancer are surgery, chemotherapy, and radiation. Surgery, however, is the most common treatment for all stages of colon cancer. Surgery is an operation to remove a segment of the intestine containing the cancer. A doctor may remove the cancer using several types of surgery.
Chemotherapy is the use of anti-cancer drugs to kill cancer cells. Chemotherapy may be taken by mouth, or it may be put into the body by inserting a needle into a vein or muscle. Chemotherapy is called systemic treatment because the drugs enter the bloodstream, travel through the body, and can kill cancer cells throughout the body.
Edited by John M. Daly, MD, Fellow of The College of Physicians of Philadelphia, and Professor of Surgery and Dean, Temple University School of Medicine