NIMG-67. ADVANCED PERFUSION AND DIFFUSION MR IMAGING IN GLIOBLASTOMA PATIENTS TREATED WITH TUMOR TREATING FIELDS (TTFIELDS) AS FIRST-LINE THERAPY

Abstract

BACKGROUND: Tumor treating fields (TTFields) is an antimitotic and FDA-approved first and second-line therapy for patients with glioblastoma. In recurrent glioblastoma, it has been reported that imaging response to TTFields is generally delayed (∼158 days), where 44% of responders developed initial tumor growth on standard imaging. However, there are currently no published reports containing a systematic review of imaging with regards to response in patients treated with TTFields as a first-line therapy. The aim of this preliminary analysis is to examine the potential of advanced imaging as an early response indicator. METHODS: Advanced MRI was evaluated in 8 patients with newly diagnosed glioblastoma after completing concomitant chemoradiotherapy followed by adjuvant temozolomide in combination with TTFields. When available, FLAIR volume (FV) and enhancing tumor volumes (ETV) were examined with diffusion (ADC) and DSC-perfusion (standardized rCBV, normalized CBF) within 90 days following initiation of TTFields. In addition fractional tumor burden (FTB), a recently described DSC-perfusion biomarker, was compared. RESULTS: Although not significant and likely due to the smaller sample size, standardized rCBV, FTB, and ADC had a nearly 2-fold or better correlation with progression free survival (r = -0.56, -0.63, 0.76) than ETV, FV and CBF (r = -0.34, -0.31, -0.38). CONCLUSIONS: The results of this study show that while standard morphologic imaging does not correlate with response to upfront TTF therapy, during the first 90 days, advanced imaging has the potential to identify responders earlier. Further analysis in a larger, prospective cohort is underway, where future goals include determining the optimal imaging time frame that best predicts response to treatment and improved survival.