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Wednesday, February 04, 2004The new test, expected to be available in the next few months, could have a big effect on public health if it works as advertised. That is because when ovarian cancer is caught early, when it is treatable by surgery, more than 90 percent of women live five years or longer. But right now, about three-quarters of cases are detected after the cancer has advanced, and then only 35 percent of women survive five years. Ah, but here's the rub. If ovarian cancer is detected early, do those women get cured, or do they end up living the same number of years as women whose cancer is discovered later, at more advanced stages? In other words, do all they get from the test is the advantage (?) of living their asymptomatic years with the knowledge that they have cancer? But, even putting that concern aside, there's plenty of reason to doubt the usefulness of this test: When the technique was first tried on 116 blood samples from women whose disease status was already known, it correctly detected all cases of ovarian cancer, including 18 in the earliest stage. It classified only 5 percent of the noncancerous samples as cancerous. When the results were published in the medical journal Lancet in 2002, it suggested a powerful testing method was at hand. ...But experts say OvaCheck must give virtually no false positives to make it useful for general screening. Fifteen women out of 100,000 get ovarian cancer each year, said Dr. Beth Y. Karlan, director of gynecologic oncology at Cedars-Sinai Medical Center in Los Angeles. So if OvaCheck were used for yearly checks on the whole population, even a 1 percent rate of false positives would mean 1,000 false diagnoses for every 15 cases detected. When you consider that a false postive can only be determined by performing a biopsy (which for ovaries means abdominal surgery), you realize at what a high cost they come, both in terms of money and health risk. But that's not all. The test isn't exactly reliable, even in the lab: The Lancet data could not be reproduced exactly even by the test developers. They found that the mass spectrometer they used, which was made for research, not high-volume work, produced different patterns even when the same samples were tested on different days. So they switched to a new machine. Sounds like a lot of false hope, and a chance for some to make a handsome profit off the worried well. (The test is expected to cost from $100 to $200) NOTE: The original Lancet paper can be found here. posted by Sydney on 2/04/2004 08:02:00 AM 0 comments 0 Comments: |
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