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strong and become statistically significant. (For AR-V7-negative patients, 16.9 months on ARS inhibitors vs. 9.7 months on taxanes, with a p value of .02; for AR-V7-positive patients, 14.3 months on taxanes vs. 5.6 months on ARS inhibitors, a p value of .03.)
While the Epic test is not FDA approved, Dittamore says the “collective experience” from several recent studies should help doctors make treatment decisions. There was Scher’s previous work, as well as a prospective, 120-patient study called PROPHECY, presented earlier this month, showing AR-V7-positive patients do not survive as long and do not benefit from taking a second ARS inhibitor. The study used Epic’s test as well as one that uses a different detection method, developed at Johns Hopkins, licensed to Dutch diagnostics firm Qiagen (NYSE: QGEN) and available only for research, not clinical use. “Both assays actually performed quite well in predicting response to standard-of-care therapy,” said the study’s lead investigator Andrew Armstrong of Duke University. “Most importantly [they] predicted overall survival.”
Armstrong noted that in PROPHECY, a negative AR-V7 result didn’t guarantee a good response from a second ARS inhibitor. “More work needs to go into precision medicine approaches to understand how tumors evolve over time,” he said in a video interview.
However quickly the Epic test is adopted, Soule is impressed by the technology behind it. “AR-V7 in the nucleus of the tumor cell is a bad sign,” he says. “The test is telling us a lot.”
Nucleus Detect it is not a genetic test. It takes snapshots of every tumor cell collected from a blood sample and uses software to determine if AR-V7 is present in the nucleus of the cell.
Soule also notes that other types of treatments for these particular patients are in development, so the decision—to go either with chemotherapy or with another ARS inhibitor—might become more complicated in coming years.
Scher says “it’s a very common decision” that he and his colleagues must make, faced with patients who fail a first ARS inhibitor. “It’s important to understand how to use these drugs.” While the test doesn’t account for every possible option, now or in the future, says Scher, “the fact that a liquid biopsy test goes this far is pretty impressive. This is an important milestone.”
Photo by Neeta Lind via a Creative Commons 2.0 license.