Colon cancer kills nearly 50,000 Americans every year, more than any other cancer except lung cancer. The death rate from cancers of the colon has not decreased over the past ten years. The disease equally affects men and women. Once the cancer is detected, the death rate from the disease is high. Fortunately, with the screening and early treatment methods now available, many of these deaths could be prevented.
Cancers of the colon usually begin as benign growths known as polyps deep within the bowels. Polyps develop slowly over a number of years into invasive tumors. With regular screening and removal of polyps when they are found, it’s estimated that the incidence of colon cancer could be reduced by at least 80 percent.
In the majority of cases, there are no noticeable signs until the cancer has advanced too far to be treated effectively. That’s why screening is so important. The American Cancer Society recommends screening of all Americans every year starting at age 50. If a person has a higher-than-average risk of colon cancer or if symptoms exist, screening should be done earlier than age 50. Three conditions place an individual at high risk for colon cancer. These include anyone with a first-degree relative diagnosed with colon cancer, persons who have been treated for cancer, and those who have bowel diseases such as ulcerative colitis. Warning symptoms that justify early screening include a change in bowel habits, blood in the stool, unexplained anemia, or weight loss.
Among the variety of screening options available, most medical groups recommend a combination of yearly fecal occult blood testing (FOBT) plus periodic examination of the colon through use of a scope. A scope is a thin, lighted tube that is inserted into the bowel through the anus. Examination can also be performed through a double contrast barium enema.
Fecal occult blood testing has the advantage of being inexpensive and non-invasive. It requires that the patient collect a series of stool samples. The samples are then examined in the laboratory for the existence of blood that can be seen only with a microscope.
Blood in the stool may indicate a bleeding polyp, but false positives can occur because the patient has hemorrhoids or has eaten red meat or other foods prior to testing. Unfortunately, bleeding is more likely to occur relatively late in cancer development, so some early cancers go undetected with FOBT alone.
Regular Screening Saves Lives
According to results of a 1993 study, yearly FOBT resulted in a 33.4 percent reduction in colon cancer deaths, although some of these were attributed to good fortune–the discovery of a non-bleeding cancer through colonoscopy as a consequence of a false positive result. Testing every other year also reduced mortality, but to a lesser degree.
Sigmoidoscopy, which allows examination of the lower third of the colon, costs about $150 and can be performed with only minor discomfort in the doctor’s office. According to one study, the combination of FOBT and sigmoidoscopy detected 76 percent of early cancers.
Colonoscopy is not only more sensitive but allows the doctor to visualize the entire colon and remove any polyps that might be found. It is considered the gold standard screening method but is more invasive, costs about $800 and requires anesthesia.
A typical recommendation is FOBT once a year plus sigmoidoscopy every five years or colonoscopy every 10 years.
Most patients describe these procedures as uncomfortable rather than painful; nevertheless, there is considerable reluctance to have them performed. A Centers for Disease Control telephone survey found that only 44 percent of Americans age 50 or over had been screened with FOBT within the past year or with flexible sigmoidoscopy or colonoscopy within the past five years.
Two promising new methods offer the hope that screening may soon become more widely accepted. These options, virtual colonoscopy and DNA testing are less invasive ways of detecting a problem.
Virtual colonoscopy uses a computerized tomography (CT) scan to examine the colon without the use of a scope–and the accompanying risk. However, like sigmoidoscopy and colonoscopy, this procedure requires that the patient empty the bowels through food restriction, laxatives and enemas. Many people do not like to undergo this preparation process. In addition, if polyps are found, this method does not allow removal during the same procedure.
An even less invasive method involves laboratory testing of a stool sample to detect changes in DNA. Early studies of the test found a 91 percent sensitivity for cancer.
If a polyp or early cancer is found, colonoscopy can be used to remove the lesion without cutting through the abdominal wall. The patient may then require more frequent screening and monitoring.
Studies have proven that maintaining a healthy weight and exercising regularly help prevent development of colon cancer. Still the most useful way of preventing the development of colon cancer is early detection and treatment before the condition progresses.
