NEW YORK -- Scientists have taken a key step toward revealing the causes
of prostate cancer, finding that a combination of five gene variants
dramatically raises the risk of the disease. Added to family history, they
accounted for nearly half of all cases in a study of Swedish men.
The discovery is remarkable not just for the big portion of cases it might
explain, but also because this relatively new approach -- looking at
combinations rather than single genes -- may help solve the mysteries of many
complex diseases like cancer and diabetes that are thought to involve multiple
genes or interactions between them.
"It gives us a new way of looking at genetic risk factors," said Dr. Teri
Manolio of the National Human Genome Research Institute, the federal agency
focused on such work.
It also might lead to a blood test to predict who is likely to develop prostate
cancer. These men could be closely monitored and perhaps offered
hormone-blocking drugs like finasteride to try to prevent the disease.
The Swedish results must be verified in other countries and races, where the
gene variants, or markers, may not be as common. Researchers already have plans
to look for them in U.S. men.
The markers have nothing to do with the aggressiveness of a tumor, only whether
a man is likely to develop one, so they do not help doctors tell which cancers
need treatment and which do not.
Nor did the markers correlate with levels of PSA, a blood substance often used
to gauge cancer risk. PSA is a notoriously imprecise measure, so a gene test
that independently predicts risk would be valuable, experts said.
This "eyebrow-raising study" should quickly spur more research, particularly in
blacks, who have a higher incidence of prostate cancer, said Dr. Howard Sandler,
a cancer specialist at the University of Michigan and spokesman for the American
Society of Clinical Oncology.
The study was led by doctors at Wake Forest University in Winston-Salem, N.C.,
and involved Johns Hopkins University in Baltimore and the Karolinska Institute
in Stockholm. Results were published online Wednesday by the New England Journal
of Medicine.
Prostate cancer is the most common cancer in American men and arguably the most
mysterious.
Unlike breast cancer, where variants in single genes like BRCA are known to
confer greater risk, few have been discovered for prostate cancer. In the last
year, other researchers identified five, but none individually seemed to raise
risk much.
Combinations of them did, the new work reveals.
It involved 2,893 men with prostate cancer and 1,781 similar men who did not
have the disease.
Sweden was chosen because the population is so ethnically similar and well
suited to gene studies.
