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Abstract #0513

Post-Bevacizumab &[Delta]T1 Maps Detect Residual Contrast Enhancement and Predict Survival in Recurrent Glioblastoma

Davis C. Woodworth1, 2, Timothy F. Cloughesy3, Robert J. Harris1, 2, Whitney B. Pope1, Albert Lai3, Phioanh (Leia) Nghiemphu3, Benjamin M. Ellingson1, 2

1Dept. of Radiological Sciences, UCLA, Los Angeles, CA, United States; 2Biomedical Physics, UCLA, Los Angeles, CA, United States; 3Neurology, UCLA, Los Angeles, CA, United States

Bevacizumab, a VEGF inhibitor, is a common second line treatment for glioblastoma after recurrence; however, bevacizumab results in reduction in contrast enhancement, which makes it difficult to assess true tumor burden and response to therapy. In the current study we explore the use of post-bevacizumab delta-T1 maps, where pre-contrast T1w images are subtracted from post-contrast T1w images, in 101 patients with recurrent glioblastoma. Results suggest delta-T1 maps reliably detect subtle contrast enhancement not apparent on normal post-contrast T1w images. Further, patients with a volume of delta-T1 hyperintense tumor greater than 15cc have a significantly shorter progression-free and overall survival.