Genetic variant for prostate cancer is twice as common in African-Americans

Nicholas Wade:

Scientists are reporting that they have detected a variant gene associated with prostate cancer, a finding that may make possible a diagnostic test to help decide which patients are the best candidates for aggressive treatment. The discovery by Decode Genetics, a gene-finding company based in Iceland, may also help explain why African-Americans, in whom the variant is more common, have a greater incidence of the disease.

Prostate cancer is a common disease with many different causes, both genetic and environmental. Detection of the underlying genes is difficult because each seems to have only a small effect. Several candidate genes have been identified in one family or population, but have generally not been confirmed by researchers trying to replicate the finding in other populations.

The new variant, to be described Monday in the journal Nature Genetics, was first found in Icelandic men and then detected in Sweden and in two populations in the United States. David Altshuler, a medical geneticist at the Broad Institute in Cambridge, said the result was statistically convincing and, because it was tested in four populations, "a model for how these things should be done."

The variant is carried by about 13 percent of men of European ancestry. It raises the risk of getting prostate cancer by 60 percent, compared with men who are not carriers, and accounts for about 8 percent of all cases, says a team of scientists led by Laufey Amundadottir of Decode Genetics.

Among African-Americans, the variant carries the same risk but is twice as common. This could explain "a significant part" of the reason that prostate cancer is more common in this population, said Kari Stefansson, Decode's chief executive.

Dr. Stefansson said the variant was "the first major gene in prostate cancer and the first to be replicated in many populations."

William B. Isaacs, a prostate cancer expert at Johns Hopkins University, called the new finding "very exciting" and added that until now, "there haven't really been any clear cut examples of genes identified by one group and reproduced across multiple study populations."

The new variant was not especially common in Icelandic men with a harmless enlargement of the prostate gland, called benign prostatic hyperplasia, indicating that its association was just with malignant forms of the disease. Dr. Stefansson said this might explain why African-Americans more often died from the disease, in addition to having a higher incidence than European-Americans.

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