Thursday, November 8, 2012
Why genetically profile a glioma?
A couple of weeks ago I met with representatives of Castle Biosciences regarding their proprietary gene expression profile assay for glioblastomas, called DecisionDx-GBM, as well as their multi-methylation test for grade II and III gliomas, called DecisionDX-G-CIMP. During the meeting, I brought up a crucial issue raised by a Neuropathology Blog reader. I'll quote part of the reader's comment: "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." The representative's response to this concern was that prognostication is an important part of the decision-making process that a neuro-oncologist, in collaboration with the patient, takes into account in recommending a course of treatment. For example, when should Avastin be introduced into the regimen? If a patient has a tumor with a genetic signature that has a longer median survival, perhaps the neuro-oncologist would be more likely to hold back on the introduction of Avastin, keeping it in his armamentarium for later in the disease course. I would add that if I personally had the misfortune of being diagnosed with a glioblastoma, I would like to have as much prognostic information as possible just to help me adjust psychologically to dealing with the the disease. I realize that one individual can fall at any point on a survival curve. But put yourself in the patient's shoes for a moment. Wouldn't you want this test done, as well as IDH1 mutation, MGMT methylation status, 1p/19q testing, and whatever else that might be available to get as much information as possible about this disease has invaded you? Since, as Castle Biosciences states, insurance will cover this test, I see both practical and intangible benefits to doing it. I would be curious to hear what other neuropathologists have to say about this issue in general and about the Castle Biosciences tests in particular. I should note that the Castle tests were developed by the widely-respected neuropathologists Dr. Kenneth Aldape at MD Anderson. I am seriously entertaining the idea of routinely using the Castle Biosciences tests at my institution and would be interested in the advice of the neuropathology community as a whole regarding this issue. Please post to comments.