Apparent Diffusion Coefficient in recurrent Glioblastoma treated with Bevacizumab Oscar S. Chirife, Teresa Pujol, Joan Berenguer, Javier Moreno, Izaskun Valduvieco, Eugenia Verger, Laura Oleaga.

BACKGROUND Glioblastomas (GB) are the most aggressive and lethal primary brain tumors. Treatment with bevacizumab (BV) for recurrent GB in patients treated with standard radiotherapy (RT) and temozolamide (TMZ) has demonstrated in different studies a significant overall survival. The Apparent Diffusion Coefficient (ADC) as a imaging biomarker has been correlated with prognosis in newly diagnosed gliomas.

To evaluate ADC values in patients with recurrent GB treated with BV. To correlate ADC with clinical and radiological response, progression-free (PFS) and overall survival (OS). PURPOSE

MATERIAL AND METHODS PATIENTS Ten consecutive adult patients with proven recurrent or progressive GB after RT/ TMZ therapy determined by the RANO criteria and treated with BV, were enrolled. Clinical status was assessed using the Karnofsky Performance Scale (KPS).

IMAGING PROTOCOL Sagittal 3D T1W Diffusion Tensor imaging (30 directions) Axial T1W SE Axial FLAIR SWI Sagittal 3D T2W TSE First-pass echo-planar dynamic susceptibility-weighted contrast-enhanced (DSC) Sagittal 3D T1-weighted +Gad Axial T1W SE post Gad

MR ASSESSMENT Both pre and first post BV MR were analyzed. The evaluation was performed by two experienced neuroradiologists active members of the multidisciplinary brain tumor board (LO y TP).

STATISTICAL ANALYSIS The correlation of the ADC value with the response to BV was evaluated using the Fisher’s exact test PFS and OS were correlated with the ADC values using Kaplan-Meier and log-rank test Statistical analyses were performed using the statistical package SPSS 17

RESULTS Mean (range) Age59 (40-74) KPS80 (50-100) FPS (months)6 (1-11) OS (months)8 (1-13) mADC CONTRAST ENHANCEMENT PRE BV 1297 ( ) lowADC CONTRAST ENHANCEMENT PRE BV 828 ( ) mADC FLAIR ABNORMALITY PRE BV 1387 ( )

ADC VALUES AND PROGRESSION

CONCLUSIONS Patients with high ADC values (mADC> mm 2 /s and lowADC> mm 2 /s) in the pretreatment study show a higher OS, and can be useful to predict survival in patients with recurrent GB treated with bevacizumab. This is a preliminary study (working progress) and more patients should be included to confirm results.

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