Blood Test Predicts Cancer Risk
Gene-Based Screen Detects Telltale Signs of Prostate, Kidney Cancer
April 19, 2005 (Anaheim, Calif.) -- A simple blood test can predict whether men are at heightened risk for prostate and kidney cancer, researchers report.
The novel test, which looks for telltale signs of cancerous changes in genes, was described at the annual meeting of the American Association for Cancer Research.
Genetic tests typically look for potentially cancerous changes in the cell's nucleus, home to most of our DNA. But the new test looks for mutations in the mitochondrial DNA, says John A. Petros, MD, associate professor of urology at Emory University School of Medicine in Atlanta.
Mitochondria are often called the cells' powerhouse; they produce the energy needed for cells to function. They also contain a small amount of DNA that is passed from mother to child.
Studies have linked nine suspected patterns in the genes of the mitochondria of men with prostate and kidney cancer, Petros tells WebMD.
Genetic Changes Double Cancer Risk
In the new study, Petros homed in what he says was the most likely candidate -- a genetic signature dubbed haplotype U.
The study included 121 men with kidney cancer, 221 men with prostate cancer, and 246 men without cancer. All the men were white Americans.
A specific variation in mitochondria DNA was found to be higher in men with cancer than in men without cancer.
"We found that haplotype U was present in 9.4% of the general population but 16.7% of prostate cancer patients and 20.7% of kidney cancer patients," Petros says.
What this means, he says, is that men who are white and who test positive for this genetic signature are at about twice the risk of prostate and kidney cancer as other white men.
"That places over 20 million men in the United States in this high-risk group," Petros says.
He suggests all white men have the test. Though it is not yet available commercially, the test can be performed in any academic, clinical, or private lab, he says.
So what do you do if you test positive? Petros recommends extra vigilance in screening for the cancers.
"You should have a serum PSA and digital rectal exam to look for prostate cancer and a CT or ultrasound scan to look for signs of renal cancer," he says.
"There's no downside to having the test," Petros says. "It's so low risk, all you need is a drop of blood. If you're told you're high risk, you get confirmatory testing that shows whether you really have cancer or not."
But Timothy Richard Rebbeck, PhD, says though the approach is really promising, it's nowhere near ready for prime time.
"It still has to be validated in a larger number of people," he tells WebMD. "This is still basic science."
There are some real downsides to being told you have cancer when you don't or vice versa --unneeded anxiety or a false sense of security being just two, says Rebbeck, professor of epidemiology at the University of Pennsylvania in Philadelphia and moderator of a news conference that discussed the findings.
Eventually, though, mitochondrial DNA testing may prove truly useful, he says. "Mitochondrial DNA are involved in cell repair. So you might hypothesize that a cell with out-of-control mitochondria would be more prone to become a tumor," he says.