Study Finds Possible Genetic Indicator of Colorectal Cancer

THURSDAY, June 18 (HealthDay News) -- Scientists say they may be moving closer to developing a genetic test for colorectal cancer that could indicate who needs a more advanced colonoscopy screening.

In a study released this week, an international team of researchers report that they've found a genetic red flag that indicates the presence of cancer more than half the time.

The research is in its preliminary stages. But "molecular genetics will likely be the future of colon cancer screening," predicted cancer specialist Dr. Jerald Wishner.

The American Cancer Society estimates that 106,100 new cases of colon cancer and 40,870 cases of rectal cancer are diagnosed in the United States each year. Nearly 50,000 people are expected to die of the diseases this year.

The death rate has been dropping over the past two decades, possibly as a result of better screening. But colonoscopies, which look for suspicious polyps, often miss tumors.

Among other things, colonoscopies might not detect small polyps, and their success depends on the skill of the person performing the procedure, said Wishner, director of the colorectal cancer program at Northern Westchester Hospital in Mount Kisco, N.Y.

There are other challenges. The cost convinces some people to avoid colonoscopies, and there aren't enough gastroenterologists to perform all that are necessary, said Dr. Scott Kopetz, an assistant professor in the Department of Gastrointestinal Medical Oncology at the University of Texas M.D. Anderson Cancer Center.

And, he said, people also avoid colonoscopies because of the inconvenience and discomfort.

Enter the idea of genetic screening, which could make colorectal cancer easier to detect by finding signs of the disease in the body's cells.

In the new study, published online June 17 in the Journal of the National Cancer Institute, researchers in the Netherlands, Belgium and the United States looked for genetic signs that appeared in cancerous colorectal cells and tissue but not in those from healthy people.

"The gene-based tests are based on the assumption that a tumor will shed cells into the stool," said Dr. Gad Rennert, who wrote a commentary on the study.

"These cells, when isolated from the stool which is collected at home, have genetic characteristics which can be identified and suggest that there is risk," said Rennert, director of the CHS National Israeli Cancer Control Center.

The researchers found that one genetic red flag indicated colon cancer 53 percent of the time in stool samples.

That may sound like a promising number. But it isn't strong enough to turn the test into a useful screening tool and is no better than current methods of testing for blood in the stool, Kopetz said.

In the future, however, genetic tests hold promise because they are cheaper and easier on patients than colonoscopies, Kopetz said. "If the stool-based test came back abnormal, then a patient would be referred for a colonoscopy," he said.

More information

The American Cancer Society has more on colorectal cancer.

SOURCES: Jerald Wishner, M.D., director, colorectal cancer program and colorectal surgery, Northern Westchester Hospital, Mount Kisco, N.Y.; Scott Kopetz, M.D., assistant professor, Department of Gastrointestinal Medical Oncology, University of Texas M. D. Anderson Cancer Center, Houston; Gad Rennert, M.D., Ph.D., director, CHS National Israeli Cancer Control Center, Haifa, Israel; June 17, 2009, Journal of the National Cancer Institute

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