The humble stool sample can be much more valuable than most people think. By carefully sifting through the genetic content of stool samples, researchers have developed a test that can detect colon and rectum in their early, most curable stages.
Although colorectal cancer is highly curable when caught early, it remains the second leading cause of cancer death in the United States. This is because many people do not seek preventive screening. The most effective tool detection is colonoscopy, which requires doctors to snake 2 meters long endoscope into the large intestine (slowly around curves, please) to look for abnormalities and tumors. In addition to being significantly uncomfortable, colonoscopies are also expensive. A simpler method of screening, analysis of blood samples for traces of stools (a symptom of colorectal cancer) is rarely conclusive.
The new technique involves testing samples of stool of a gene called CPA . Movements CPA can trigger the growth of tumors and mutated CPA is found in almost all malignant colorectal tumors. Now oncologists Bert Vogelstein and Kenneth Kinzler and their team at the Kimmel Cancer Center at Johns Hopkins University in Baltimore have shown that mutant CPA DNA can be detected in necrotic cells of the intestinal mucosa in faeces . The team used PCR - the standard method for DNA replication - to amplify the CPA DNA in stool samples from 74 patients. Samples containing mutated CPA dysfunctional protein gene products, allowing them to be easily identified.
The precise detected mutated ART CPA DNA in 61% of patients already diagnosed with cancer of precancerous colon at an early stage and identified mutations in 50% of patients known to have tumor benign, the team reports in the January 31 the New England Journal of Medicine . The test produced no false positives for a group without cancer.
"This work must absolutely be prosecuted," said Barbara Conley, an oncologist at the National Cancer Institute in Bethesda, Maryland. Although Conley stressed that more work needs to be done to improve test sensitivity she said it could one day provide a welcome alternative to colonoscopy.
Related Sites
Vogelstein / Kinzler Laboratory
information on colon cancer NCI
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