August 27, 2008
Medical Experts Not Sure About OvaSure
A new blood test aimed at detecting ovarian cancer at an early, still treatable stage is stirring hopes among women and their physicians. But the Food and Drug Administration and some experts said the test has not been proved to work.
The test, called OvaSure, was developed at Yale University and has been offered since late June by LabCorp, one of the nation's largest clinical laboratory companies.The need for such a test is immense. When ovarian cancer is detected at its earliest stage, when it is still confined to the ovaries, more than 90 percent of women will live at least five years, according to the American Cancer Society. But only about 20 percent of cases are detected that early. If the cancer is detected in its latest stages, after it has spread, only about 30 percent of women survive five years.
But far from greeting the new test with elation, many experts are saying it might do more harm than good, leading women to unnecessary surgeries. The Society of Gynecologic Oncologists almost immediately issued a statement saying it did not believe the test had been validated enough for routine use.
"You've got industry trying to capitalize on fear," said Andrew Berchuck, director of gynecologic oncology at Duke University and the immediate past president of the society. "We'd all love to see a screening test for ovarian cancer," he added, "but OvaSure is very premature."
OvaSure's debut also raises questions about whether greater regulation is needed to ensure the validity of a trove of sophisticated new diagnostic tests that are entering the market and are being used as the basis for important treatment decisions. OvaSure did not go through review by the FDA because the agency generally has not regulated tests developed and performed by a single laboratory, as opposed to test kits that are sold to laboratories, hospitals and doctors. (All OvaSure blood samples are sent to LabCorp for analysis.)
But the FDA has now summoned LabCorp to discuss OvaSure, saying the data appears insufficient to back the company's claims about the test. "We believe you are offering a high-risk test that has not received adequate clinical validation and may harm the public health," the agency said in an Aug. 7 letter sent to LabCorp that was posted on the FDA Web site. A spokesman for LabCorp, which is short for Laboratory Corp. of America Holdings, said the company looked forward to reviewing the data with the agency but would continue offering the test in the meantime.
Myla Lai-Goldman, chief medical officer of LabCorp, said that OvaSure had been validated in several studies and that additional data were expected by the end of this year. Diagnostic tests typically are studied further after they have reached the market, she said. Goldman said there was "tremendous interest" from physicians in learning more about OvaSure.
Patients and advocacy groups seem divided on OvaSure, which costs about $220 to $240.
"We are hearing from people that they are very excited about it," said Cara Tenenbaum, policy director for the Ovarian Cancer National Alliance. But the alliance urges women to wait for more data before relying on the test.
More than 21,000 new cases of ovarian cancer will be diagnosed in the United States this year, and more than 15,000 people are expected to die from the disease, the American Cancer Society said.
OvaSure measures the level of six proteins in a sample of blood, some produced by a tumor and some produced by the body in reaction to a tumor. It then calculates a probability that the woman has ovarian cancer. One of the six proteins is CA-125, which is used by itself as a test to monitor disease progression in women who already have ovarian cancer but is not good at picking up early disease.
In a study published in the journal Clinical Cancer Research in February, the test correctly classified 221 of 224 blood samples taken from women with ovarian cancer or from controls. It identified 95 percent of the cancers, and its false positive rate - detecting a cancer that was not there - was 0.6 percent.
But Beth Karlan, director of the Women's Cancer Research Institute at Cedars-Sinai Medical Center in Los Angeles, said the samples tested were not representative of what might be encountered in routine screening. There were very few blood samples from women with early stages of the most deadly type of ovarian cancer. "That's really what we want to find," she said.
The biggest concern is not that the test will miss cancers but that it will say a cancer is there when it is not. That would then subject women to needless surgery to have their ovaries removed.
Berchuck of Duke said only 1 of 3,000 women has ovarian cancer. So even if a screening test had a 1 percent rate of false positives, it would mean that 30 out of 3,000 women tested might be subject to unnecessary surgery for every one real case of cancer.
Teresa Hills, who had a visible mass on her left ovary, got a positive result from OvaSure. But when the ovary was removed, the mass turned out to be benign.
The false positive did not prompt unnecessary surgery because Hills was going to have the mass removed in any case. But it did cause needless anxiety.
"You can't sleep. You can't eat. You're paralyzed with fear," said Hills, a 44-year-old mother of three from Rockford, Ill. She said she lost 10 pounds in two weeks after the false diagnosis.
Lai-Goldman at LabCorp said that OvaSure should be restricted to women at high risk of ovarian cancer and that the test should be repeated if the result is positive. Those measures would limit the number of false positives.
LabCorp estimates that there are 10 million women at high risk. These include carriers of mutations in genes called BRCA1 or BRCA2, as well as women with histories of ovarian or breast cancer.
Gil Mor, the lead developer of the test at Yale, said the use of OvaSure might reduce ovarian surgeries, not increase them. That is because women with BRCA mutations often have their ovaries removed to prevent cancer. A negative result on the OvaSure test might allow such women to put off the surgery.
"They are removing the ovaries without the test," said Mor, an associate professor of obstetrics and gynecology. "So what are we talking about here? We are trying to do the opposite and say don't remove the ovaries."
The ovarian cancer detection field has had disappointments before. Four years ago, the FDA intervened to effectively stop the marketing of another complex ovarian cancer screening test.
The test, called OvaCheck, had also spurred great hope but never made it to market as experts questioned its validity.
Originally published by The New York Times.
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