New ovarian Ca screening test to debut next month: targets high-risk women: critics concerned that OvaCheck's accuracy rates remain unpublished

OB/GYN News,  Feb 15, 2004  by Michele G. Sullivan

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A new test to screen patients at high risk for ovarian cancer is slated for release next month.

But critics say the test, to be marketed as OvaCheck, may not replicate the high accuracy rates shown in studies of a similar test on which it is based.

OvaCheck, developed by Correlogic Systems Inc., identifies a very specific metabolite pattern that has been found to occur in the blood of women with ovarian cancer, even at very early stages.

A similar test, which involved a different molecular pattern, was the subject of a landmark 2002 study. That study of 216 women showed that the protein pattern--based test had a specificity of 95% and a sensitivity of 95%, with a positive predictive value of 94% (Lancet 359 [9306]:572-77, 2002). OvaCheck was developed on the basis of this test.

However, OvaCheck's rush from research to market, and the fact that its accuracy rate remains unpublished, worry Dr. Robert Bast Jr., who is vice president for translational research at the University of Texas M.D. Anderson Cancer Center, Houston.

"With any new test, it's crucial that we have a large enough patient sample to know what the true value is," he said. "There is no published data on the accuracy of this test and until there is, I don't see how anyone can recommend its use."

Correlogic and LabCorp, one of the two national labs that will process the test, are working together, validating the test with a series of blind samples.

LabCorp would not comment on the validation studies or when those data would be released, other than to say the test is performing "just as well as we had hoped."

"We intend to release this test by the end of March and we are very pleased with what we have seen so far," said Pamela Sherry, LabCorp's senior vice president of investor relations and corporate communications.

Peter Levine, Correlogic's chief executive officer, acknowledged that OvaCheck's accuracy might not match that of the original research.

However, he said, the new test will almost certainly outperform CA-125 in identifying ovarian cancers (sensitivity about 80%; specificity about 98%).

"No test should be relied upon 100%," Mr. Levine said. "We are giving the physician and the patient one more method to make a judgment. And as we accumulate more samples, the test will become more sophisticated."

OvaCheck is believed to measure specific proteins that indicate a host response to tumor cells, said Mr. Levine. The patterns specific to ovarian cancer patients were discovered using a sophisticated mathematical algorithm to organize proteomic spectra generated by mass spectroscopy.

In the original study, led by Emanuel Petricoin, Ph.D., of the National Cancer Institute, researchers first developed a characteristic cancer profile by comparing patterns of proteins in the blood of 50 healthy women with those of 50 women known to have ovarian cancer. The data were used to identify a proteomic pattern that discriminated cancer from non-cancer.

Researchers then searched for the same pattern in blood samples from 50 women with ovarian cancer and 66 women who were healthy or had benign disorders. The test correctly identified all cases of ovarian cancer, including 18 patients with stage I disease. It also correctly identified 63 out of the 66 women with no disease, but incorrectly indicated that 3 had the cancer.

OvaCheck, which will be offered through LabCorp and Quest Laboratories, is based on this research. However, the test uses a different mass spectrometer and looks at a characteristic pattern of metabolites rather than the pattern identified in the original study.

While Correlogic needs to perform its own validation studies, the science behind OvaCheck is sound, said Dr. Petricoin, who is the codirector of the Food and Drug Administration-National Cancer Institute Clinical Proteomics Program. He supports its development: "We are extremely happy that Correlogic is rigorously evaluating this method and that it's being made available to the patients."

Initially, the test is intended only for screening of high-risk patients, including those with a family history of ovarian cancer or male breast cancer, breast cancer survivors, and those with a BRCA1 or BRCA2 mutation or a mutation that puts them at risk for colon cancer. The test is currently designed to identify patients likely to have ovarian cancer.

But as Correlogic accumulates more data, Mr. Levine envisions it evolving into a test that also identifies disease stages.

"Right now, though, we see it as a triage tool for women at high risk," he said. "We really want to stress that the results be used as part of all the other methods used to evaluate these patients. It's one additional piece of information."

Dr. Eva Chalas, who is a gynecologic oncologist and coordinator for cancer services at the Long Island Cancer Center, Stony Brook, N.Y., agreed that the accuracy of the ovarian cancer screening test will continue to evolve.