May 20th, 2010
08:08 PM ET
By Miriam Falco
(CNN) Researchers may have found an effective way to screen for ovarian cancer by using an existing blood test in a new way, according to a study released Thursday by the American Society of Clinical Oncology).
Ovarian cancer is often called the silent killer because there is no good equivalent screening tool, like mammograms are for breast cancer. Dr. Douglas Blaney, ASCO president, calls this cancer vicious because it's usually detected after it can be cured with surgery.
For more than two decades, doctors have known that a protein called CA-125, is much more prevalent in ovarian cancer cells than healthy cells.
A blood test that looks for CA-125 is used to determine whether an ovarian cancer patient's treatment is working. However, the CA-125 test hasn't been an effective screening for ovarian cancer because many women who have high levels of this protein don't actually have cancer.
"For the last 10 years, the ovarian cancer community has been interested in screening for new [cancer] markers," says lead author Dr. Karen Lu from the M.D. Anderson Cancer Center in Houston, Texas. But when researchers compared all the new markers for ovarian cancer at a cancer conference last year, Lu says, of all the new markers, the old one – CA-125 was the best.
So Lu and her co-authors developed mathematical way to determine how the old test could be used in a new way.
For eight years, researchers followed over 3,200 postmenopausal women age 50 and older who didn't have a family history of the disease.
They started by testing the women's CA-125 levels. Based on the woman's age and depending on how high those levels were, the women were asked to get their next blood test one year later, to wait three months, or If their levels were high, they were immediately referred to ultrasound screening and a surgeon.
"What these folks are trying to do is look at change over time," explains Dr. Otis Brawley, chief medical officer of the American Cancer Society, who was not involved in the study.
Using criteria developed by the researchers, 82 percent of the women had low CA-125 levels and were told to come back in a year. They were classified as low risk.
Over the course of the study, about 7 percent of the women were judged to be at intermediate risk based on their protein levels and were asked to get tested every three months. And less than 1 percent were at high risk and sent to get an ultrasound and see a surgeon immediately.
Five women were found to have ovarian cancer, all at an early stage.
The study authors say their work provides early evidence that this new method of using the CA-125 test could be a feasible strategy for screening women over 50 years of age.
Blaney describes the results as a more refined application of known test.
Lu was cautiously optimistic about the study because it found very few false positive results and doctors were able to pick up this very aggressive cancer at an early stage giving women a much better chance of survival.
However, this study will not lead doctors to recommend all women start getting this blood test once they hit the age of 50 – at least not yet.
Because ovarian cancer is so rare, a much larger trial is needed says Lu. Ovarian cancer strikes one in 2,500 post-menopausal women – and one in 10,000 women between the ages of 35 and 50.
The definitive study is being done in the United Kingdom," say Lu.
This study involves 200,000 women and is designed to determine whether lives are actually saved by using this new application of the old test.
Results from this trial are expected in four years.
"Four years is pretty fast" says Lu.
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