New FOBT Colorectal Cancer Test Offers Hope for Early Detection
by CD Buckner M.D.
According to a report in the November issue of the journal Gastroenterology, early detection of colorectal cancer and precancerous tumors may be possible with a new screening test that involves looking for abnormal DNA in stool samples.
When detected early, colorectal cancer is a highly curable disease. Colorectal cancer begins with the development of an adenomatous polyp, which is a small benign tumor that grows in the colon. These polyps take 10 to 15 years to transform into cancer. Since this development phase is so long, screening and early detection can play a crucial role in the prevention of colorectal cancer, as detection and removal of the polyps can prevent the development of the disease.
As the polyp develops, there are changes in the tumor’s DNA. By examining tumors that have been removed from patients, researchers have identified some of these altered DNA molecules. The tumors shed cells into the intestine, which makes it possible to detect the abnormal DNA cells in stool samples.
In a recent study at the Mayo Clinic, researchers examined the stool samples of three different groups: 22 people who had been diagnosed with colorectal cancer, 11 people who had polyps, and 28 people without any colorectal tumors. They found abnormal DNA in 91% of the stool samples from cancer patients and 73% of the stool samples from the patients with polyps. None of the stool samples from tumor-free people had abnormal DNA.
The results of this study show that DNA stool testing has the potential to become an efficient screening test for colorectal cancer. This could be an accurate and non-invasive test that people might be more willing to undergo than other more intrusive and uncomfortable tests. A 3-year clinical trial funded by the National Cancer Institute is scheduled to begin in January in order to further evaluate this procedure. In the meantime, it is still important for people to utilize the existing methods of screening for colorectal cancer, which include the fecal occult blood test (FOBT), sigmoidoscopy, colonoscopy and the double-contrast barium enema. People concerned with screening for this disease can consult with their physicians for more information.
Future clinical trials will help to establish the feasibility of using DNA stool testing as a standard screening procedure. People who are at a high-risk for developing colorectal cancer may wish to speak with their physicians about the risks and benefits of participating in a clinical trial in which DNA stool testing and other promising new screening techniques are being evaluated.
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