Wednesday, September 12, 2012

DecisionDx-GBM: Should every glioblastoma patient be getting this test?

What does the neuropathology community think of DecisionDx-GBM? This is a product offered by Castle Biosciences, based in Phoenix, AZ. DecisionDx-GBM is a gene expression profile test developed at The University of Texas M. D. Anderson Cancer Center for the purpose of increasing the accuracy of the prognosis and predicted responsiveness of glioblastoma multiforme to first line radiation plus temozolomide. The test is able to distinguish GBM tumors with a proneural phenotype (tumor signature) from those with a mesenchymal / angiogenic phenotype. Patients with a proneural phenotype tumor who are treated with first line radiation plus temozolomide experience a significantly longer median survival (over 7 years) compared to those patients with a mesenchymal / angiogenic phenotype tumor (approximately 1 year). According to the company website, the assay has been fully validated and has been available for clinical use since 2008. A study is ongoing to determine whether the tumor molecular profile conferring a mesenchymal/angiogenic phenotype is associated with a selective increase in benefit from the addition of bevacizumab to temozolomide and radiotherapy. DecisionDx-GBM is also currently being incorporated into a number of other prospective and retrospective studies.

Is DecisionDx-GBM covered by insurance? Castle Biosciences states that the test receives reimbursement from a number of commercial insurance companies, and appeals to the Administrative Law Judge level for Medicare have resulted in favorable decisions for full payment. Should a patient need to pay out-of-pocket for this test, I could not find on the website what the cost would be.

Should we as neuropathologists recommend the use of this profile? Here is a an example of the kind of report that is generated when one orders the panel of 12 genes (3 of which are for control) upon sending a block of paraffin-embedded fixed tissue to the company. I would be interested in hearing people's opinions regarding this product, and whether there are others on the market which might be comparable. Please post!


shipcolldoc said...

It is standard of care to give radiation + concurrent temozolomide, followed by "maintenance" temozolomide, for patients with glioblastoma (or other high grade gliomas). Nobody will get a different treatment based on the results of this test unless they are going to enter a clinical trial, and the trial would determine what predictive/prognostic testing should be done for study entry. I doubt anyone wants to give a patient a life expectancy prediction based on the results of this test, since individuals may fall at any point on a survival curve. So I would not be eager to recommend this test until there are alternative treatments for those in poor prognosis groups.

Brian E. Moore, MD, MEd said...

Good points all, shipcolldoc. I am meeting with a representative of the company that offers DecisionDx-GBM next month, and will ask for his reaction to your comment.

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