May 20, 2010 -- A new screening approach shows promise for the detection of ovarian cancer in postmenopausal women at average risk of the disease, early testing suggests.
The strategy uses a mathematical model that combines a patient's age and changes in blood levels of a protein called CA-125 over time to estimate risk of ovarian cancer.
In a study of more than 3,200 postmenopausal women, the approach proved feasible, with "very, very few false-positive results," says study researcher Karen Lu, MD, professor of gynecologic oncology at The University of Texas M.D. Anderson Cancer Center in Houston.
Still, many other approaches that looked promising in early tests have turned out to be false starts, she tells WebMD.
The findings were presented at a news briefing held in advance of the annual meeting of the American Society of Clinical Oncology (ASCO).
About one in 2,500 postmenopausal women develops ovarian cancer, which is the most deadly gynecologic cancer, Lu says.
The reason: More than 75% of cases are diagnosed at an advanced stage, when cure rates are less than 30%.
"If caught at an early stage, cure rates are 60% to 90%," she says.
As a result, the search is on for an early, reliable screening test for early-stage disease. Years ago, researchers discovered that blood levels of the CA-125 (cancer antigen-125) protein are elevated in women with ovarian cancer. But by itself, CA-125 did not prove useful as an early marker, Lu says.
"While 80% of advanced ovarian cancers have elevated CA-125 levels, only half of early-stage cancers have elevated CA-125 levels," she says.
Plus, CA-125 levels are elevated in women with other cancers, benign ovarian tumors, and pelvic infections, Lu says.
The blood test for CA-125 is currently used to check to see if treatment is working or if cancer has returned.
Recently, researchers started looking at the change in CA-125 levels over time rather than at CA-125 as a single value, Lu says.
"We and others theorized that if someone has low levels and they double, it could be a sign that something is happening even if levels are still low. Alternately, if a woman has a high value and it stays there, [we theorized] it's not likely to be ovarian cancer," she says.
For the new study, the researchers evaluated the "Risk of Ovarian Cancer Algorithm" (ROCA), based on a patient's age and changes in CA-125 blood levels results over time.
Women with the greatest change in CA-125 levels are referred for transvaginal sonography (TVS), and, when needed, to a gynecologic oncologist to determine if surgery is necessary.
The study included 3,238 postmenopausal women aged 50 to 74 without a family history of breast or ovarian cancer. They were followed for up to nine years.