Causes and Treatment
Colorectal cancer is the third-most common cancer in men and women in this country, and the second leading cause of cancer death after lung cancer. It kills more people (56,000 annually) than either breast or prostate cancer. The latter two diseases, however, appear to instill more fear in people, which has translated into greater awareness and higher rates of screening for early detection. Ironically, says Mayer, the screening tests for colon cancer are significantly more accurate than those for breast or prostate cancer.
Robert Mayer, MD
Only about 10 percent of colorectal cancers are due to inherited genes that create a marked susceptibility to the disease. Another 20 percent occur in people who have a strong family history of the illness, which increases their risk — but not to the level of inheriting a susceptibility gene. The remaining 70 percent of colon cancers are found in people with no known risk factors — which is most of the population.
Colon cancer, diagnosed mainly in people over age 50, develops over many years as a succession of colon cell genes becomes damaged (mutated) and allows for abnormal cell growth. The first, precancerous stage that can be easily identified is "adenomatous polyps" — fleshy growths — on the inside lining of colon or rectum. Over four more years, can turn into actual cancers that invade wall. If untreated, disease eventually spreads to surrounding tissue or, in worst case, other organs.
"This is a disease where you can really make a difference. You find the precancerous polyps, remove them, and reduce the risk dramatically of developing this cancer.
— Robert Mayer, MD, director of Dana-Farber's Center for Gastrointestinal Oncology
When colon cancer is this far advanced, the five-year survival rate is less than 10 percent. But if detected and removed when still confined to the colon, the rate jumps to 94 percent. Currently, however, only 35 percent of colon cancer patients are diagnosed this early. "If you wait for symptoms," Syngal says, "it's too late."
The mainstay of treatment is surgery to remove the tumor and part of the bowel, if necessary. In a small number of cases, the surgeon may have to create an opening in the abdomen through which the intestinal wastes empty into a bag outside the body (a procedure known as a colostomy). When the tumor is advanced, radiation and chemotherapy are often added to help combat cancer that has spread beyond the original tumor site.
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