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UNC-CH research shows publication bias causes overestimate of cancer risk in Barrett's esophagus

August 28, 2000

CHAPEL HILL -- Estimates of the risk of esophageal cancer from a condition known as Barrett's esophagus apparently are exaggerated by the tendency of medical journals to favor articles with more dramatic results, according to a new University of North Carolina at Chapel Hill study.

Authors also say a news conference held in Washington, D.C. Aug. 24 could have unduly alarmed the public about cancer risks for people who suffer heartburn at night.

The UNC-CH School of Medicine study, published in the current issue of the journal Gastroenterology, involved reviewing 554 summaries of medical research projects and analyzing in detail the 27 most relevant to Barrett's esophagus and cancer risk.

The relatively common condition -- cellular changes in tissues lining the esophagus -- is thought to be a precursor to cancer, said Dr. Nicholas J. Shaheen, assistant professor of medicine and lead author. People who develop esophageal cancer are believed to have Barrett's first, but just because one has Barrett's doesn't mean they will go on to get the life-threatening illness.

"We found a strong correlation between the reported cancer risk and the size of the study," Shaheen said. "Small studies reported much higher risks of cancer than larger studies. The association persisted even after we accounted for multiple differences between the studies."

Between 2 million and 3 million people in the United States have Barrett's esophagus, but fewer than 10,000 a year go on to develop esophageal cancer, the physician said. Some 50 million Americans experience heartburn at night.

"For that reason, any single person experiencing reflux has a very small risk of cancer," Shaheen said."The American Gastroenterology Association news conference in Washington, D.C., mentioning the risk of cancer in those with nighttime heartburn has the potential to unduly scare a lot of people. "The general public is extremely unlikely to get esophageal cancer, even if they have reflux."

Others involved in the new study were Drs. Melissa A. Crosby, a first-year resident, and gastroenterologists Eugene M. Bozymski and Robert S. Sandler, both professors of medicine. Most doctors recommend that patients with Barrett's esophagus undergo endoscopy examination every year or two to keep an eye on affected tissue.

"We're doing endoscopies every two years on these patients until further data come out to help direct us," Shaheen said.

Researchers at UNC-CH conducted their study to help the medical community understand whether or not widespread testing is warranted.

"If the risk is low, we're wasting a lot of money and a lot of time screening everybody," Shaheen said. "If the risk is high, then it is money well spent, kind of along the lines of mammography looking for breast cancer. Our bottom line is that the scientific literature probably overestimates the risk and that the risk is very low. Although the risk is higher in those who have heartburn at night, the chances still are slim."

Shaheen, who directs UNC-CH's Center for Esophageal Diseases and Swallowing, said "tons and tons of people worry every time a news report about cancer risks crops up."

"Truth be told, these cancers are pretty rare," he said. "Even if a person has 11 times the risk as the general public, if the cancer is that rare, his or her chances of getting it are still very small."

By contrast, close to two million Americans, mostly women, have breast cancer, according the National Cancer Institute.
-end-
Note: Shaheen can be reached at (919) 962-2513.
Contact: David Williamson, 962-8596.

By DAVID WILLIAMSON
UNC-CH News Services

University of North Carolina at Chapel Hill

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