Personal Gene Mapping Has Limits, Study Says04/02/12
MONDAY, April 2 (HealthDay News) -- Many people have pinned
their hopes on human genome scans as the cornerstone of the rapidly
emerging field of personalized medicine, able to predict the future
health of individuals.
But there may be limits to what information whole genome
sequencing can provide, according to new research slated for
presentation Monday at the American Association for Cancer Research
annual meeting in Chicago. The study will be simultaneously
published online in
Science Translational Medicine.
"In most cases, genome sequencing is not going to tell people what disease they're going to get or die from. It can be valuable in telling what diseases they have an excess risk for," said study co-author Dr. Bert Vogelstein, director of the Ludwig Center for Cancer Genetics and Therapeutics at Johns Hopkins University in Baltimore.
"Genome sequencing is not going to be the dominant component of patient care," he added. "It will not be a substitute for preventive medicine strategies incorporating routine check-ups, exercise, physical status, lifestyle."
The costs of whole genome sequencing are plummeting, making the
test more accessible to more people, yet the ability of the test to
provide useful information to patients has not been studied
quantitatively, Vogelstein said.
The authors used data on identical twins in registries in
Sweden, Denmark, Finland and Norway, as well as a U.S. registry of
World War II military veteran twins, to look at genetic risk for 24
common diseases including diabetes, Alzheimer's and breast
The researchers calculated that genetic sequencing would reveal
a predisposition to at least one disease in 90 percent of the twins
But that's only predisposition, not whether you actually fall
ill or not. The actual risk of getting one of these conditions
would be no different from that of the general population, the
The analysis also concluded that most individuals would receive
negative test results for 23 of the 24 diseases but, again, this
hypothetical information would not necessarily predict the future.
Even with a negative test result, the risk for developing most of
the diseases for which one tested negative would still be 50
percent to 80 percent of that in the general population.
To put the results in context: 2 percent of women who undergo
whole genome tests will likely get a positive result for ovarian
cancer risk, explained Vogelstein, who is also an investigator at
the Howard Hughes Medical Institute, in Chevy Chase, Md.
That puts their overall risk of developing a tumor in their
lifetime at 10 percent.
And the 98 percent of women who get a negative result don't
necessarily get a "get-out-of-jail-free pass" as they still harbor
the same risk as the general population, Vogelstein said.
If it comes down to a choice between spending money on a genome
test and spending it on health measures such as regular check-ups
and joining a gym, it might be wise to go with the latter, he
"If I spend it on a gym membership, that will definitely decrease my risk for ovarian cancer," Vogelstein said.
On the other hand, a genetic test might seem prudent for someone
with a family history of a specific disease.
Commenting on the study, Dr. Marc Williams, vice president of
clinical genetics for the American College of Medical Genetics and
Genomics in Salt Lake City, said: "There's certainly some promise
in this type of testing but we're still trying to sort out what are
the best situations in which to apply this type of whole genome
Williams pointed out that "if we broadly apply it without
thinking about the clinical context -- why we are doing the test,
what we hope to learn -- then we could get into a lot of trouble in
terms of coming up with a lot of information we don't know what to
In the end, though, said study author Vogelstein, it comes down
to an individual decision.
Human Genome Project has more on genetic
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