Introduction: Glioblastoma (GBM) is among the most malignant cancers. Current therapeutic options are palliative, involving surgical removal of the primary tumor followed by chemo and radio-therapy. Although the primary tumor is typically easily identified by Magnetic Resonance Imaging (MRI), standard treatment modalities such as surgery, radio-chemotherapy, immunotherapy and others may induce imaging changes which confounds the diagnosis of tumor recurrence. Standard MRI cannot conclusively differentiate between true GBM recurrences, pseudo progression (PP), radiation necrosis (RN) or all three. Although some groups have reported success using PET and other advanced imaging modalities, these modalities are neither routinely available nor regularly reimbursed by insurance. A brain biopsy is required to make the diagnosis and this is sometimes declined by patients.
Methods: Using a novel blood-based liquid biopsy, we have been able to longitudinally follow eight patients following surgical removal of GBM. Using an index which corresponds to the ratio between quantification of monocytic Myeloid-Derived Suppressor Cells (Mo-MDSC) and CD14+ VNN2+ cells in the peripheral blood of patients (the DVI index), we have been able to assess recurrence versus remission in all patients. While a DVI =1 is indicative of tumor recurrence, a DVI < 1 suggests remission or development of RN.
Results: DVI > 1 correctly predicted 10 biopsy-confirmed recurrences in 8 patients prior to development of symptoms. Only 4 of these cases demonstrated clear tumor progression based on the radiologists opinion, while 3 were thought to be consistent with RN, and 3 were “equivocal” according to the radiologist. Similarly, 3 patients with DVI < 1 had biopsy proven RN or PP despite radiological diagnosis of “tumor progression” according to radiologists.
Conclusions: This minimally invasive, economically viable test could be used to monitor patient’s response to treatment following GBM on a recurring basis to assess response to treatment or recurrence.
Patient Care: If additional studies confirm the diagnostic utility of DVI, we may be able to eliminate brain biopsies and markedly decrease the use of MRI
Learning Objectives: DVI can differentiate GBM recurrence from RN.