Contrast-enhanced T1-weighted subtraction maps for response assessment in recurrent glioblastoma treated with bevacizumab

• Published in: Journal of clinical oncology Vol. 31; no. 15_suppl; p. 2055
• Main Authors: Ellingson, Benjamin M., Kim, Hyun J., Woodworth, Davis C., Pope, Whitney B., Cloughesy, Jonathan N., Harris, Robert J., Lai, Albert, Nghiemphu, Phioanh L., Cloughesy, Timothy F.
• Format: Journal Article
• Language: English
• Published: 20.05.2013
• ISSN: 0732-183X; 1527-7755
• DOI: 10.1200/jco.2013.31.15_suppl.2055

Abstract only 2055 Background: Antiangiogenic therapy in glioblastoma (GBM) results in decreased enhancement on post-contrast T1w images, which complicates standard response assessment and is likely the reason no studies have found predictive value in enhancing tumor size or change in size. The current study examined whether contrast-enhanced T1-weighted subtraction maps (CE-ΔT1w) calculated from subtracting pre-contrast (T1) from post-contrast T1w images (T1+C) can improve quantification and predict response in GBM patients treated with bevacizumab. Methods: Recurrent GBM patients (n=160) from the BRAIN trial (AVF3708g), a multicenter Phase II trial evaluating bevacvizumab, were used in the current study. CE-ΔT1w maps were calculated 2 weeks before and 6 weeks after the first dose of bevacizumab by: 1) performing registration between T1 and T1+C images, 2) image intensity normalization of T1 and T1+C images, and 3) subtraction of T1 from T1+C images. The volume of tumor regions with positive contrast enhancement after subtraction was retained for analysis. Results: CE-ΔT1w maps greatly improved detectability of subtly enhancing lesions, particularly post-treatment. Results for PFS and OS are summarized in the table below. In all scenarios, CE-ΔT1w maps outperformed conventional tumor segmentation. Results show that size and change in size are both predictive of PFS and OS. Conclusions: CE-ΔT1w maps improve visualization and quantification of contrast enhancing tumor regions in recurrent GBM, allowing for more accurate response assessment. [Table: see text]