March 9, 2011 (Orlando, Fla.) -- Nearly one in four ovarian cancers are inherited, say researchers who are developing a gene-based blood test to identify women with these hereditary cancers.
The test, which looks for variations in 22 genes known or suspected to predispose women to ovarian cancer, isn't ready for prime time yet.
But if results of the new study can be replicated and the test becomes commercially available, it would be a big advance over the current genetic screen, says study head Elizabeth Swisher, MD, an expert in medical genetics at the University of Washington in Seattle.
The current test, which screens for the BRCA1 and BRCA2 genes, only spots about 10% to 15% of ovarian cancers, she tells WebMD.
The new study included 284 women who were undergoing surgery to remove an ovarian or fallopian tube tumor. All provided blood samples for DNA testing.
A total of 24% had a mutation in one or more of the 22 genes, which included BRCA 1 and BRCA2.
About three-fourths of women who tested positive for a mutation had a family history of breast or ovarian cancer. (The same genes that increase a woman's risk of ovarian cancer are usually associated with increased breast cancer risk, too.)
The results were presented at the Society of Gynecologic Oncology's Annual Meeting on Women's Cancer.
If the test does become available, who should be tested?
"If there is a family history of ovarian or breast cancer, the woman with cancer should ideally be tested first," Swisher says.
Then if she does test positive for the cancer, her daughter or other close female relatives may want to consider testing too, she says.
Swisher says she expects the new test to cost about $1,000. That’s cheaper than the BRCA1/2 test, which costs $4,000.
Jonathan M. Lancaster, MD, PhD, of the H. Lee Moffitt Cancer Center in Tampa, Fla., tells WebMD that the new research "contributes to our goal of personalized medicine."
But there's still a long way to go, he says, noting that gene-based cancer blood screens that look good in early testing don't always hold up to scrutiny.
Determining Ovarian Cancer Risk
Swisher agrees much more testing is needed. A positive result on a gene test doesn't mean you will get cancer, just that you’re at increased risk. And still unknown is the increased risk -- is it 10% or 50% or more, for example -- associated with a positive result on the 22-gene test.
Swisher says development of an experimental class of drugs called the PARP inhibitors for the treatment of breast and ovarian cancers has increased the incentive to find more hereditary cancers.
"The PARP inhibitors work on DNA repair, which is where many of these mutations occur," she says. "So presumably having mutations in these genes would make you more likely to respond to the drugs."
These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.