African-American men at higher risk.

A DNA segment on chromosome 8 that is a major risk factor for prostate cancer, especially in black males, has been identified by researchers at Harvard University Medical School, Boston.

"This genetic risk factor about doubles the likelihood of prostate cancer in younger African-American men," explains principal investigator David Reich, assistant professor of genetics. "This finding may explain why younger African-Americans have an increased risk for prostate cancer than do other populations--and may also explain why this increased risk in African-Americans attenuates with older age."

"Interestingly, we found that this region also confers risk for prostate cancer for diverse ethnic groups," notes lead author Matthew Freedman, professor of medicine. "The actual gene, however, has yet to be identified."

The researchers used their newly developed method of "admixture mapping" to screen through the genome in blacks (who have African and European ancestry), searching for the segments where individuals with disease have more of one ancestry than the average. The key epidemiological fact is that prostate cancer occurs approximately 1.6-fold times more often in African-Americans than in other populations.