P09.13 F-18 FLT PET and MRI As Outcome Predictors in Glioblastomas Following Chemoradiation Therapy

Purpose: To evaluate F-18 fluorothymidine (FLT) PET and MRI as pretreatment and post treatment biomarkers predicting progression free survival (PFS) and overall survival (OS) in patients with glioblastomas, and to discover predictors to improve stratification of patients for treatment. Materials & Methods: Twelve patients with newly-diagnosed glioblastomas who had had biopsy or subtotal resection were enrolled in a prospective clinical trial; they received baseline F-18 FLT PET and brain MRI as well as post- treatment PET and MRI at 4 weeks. Volumetric segmentation of tumor was performed on baseline FLAIR imaging and subsequently applied to T1+gadolinium contrast, T2, apparent diffusion coefficient (ADC), cerebral blood volume (CBV) images of baseline and post-treatment MRI, and to pre- and post-treatment FLT-PET images. The 10th, 25th, 75th, and 90th percentile values as well as mean signal intensity within each modality and time point were individually analyzed using the Kaplan-Meir approach to discover the best predictors of OS and PFS. Results: Several baseline MR parameters (mean and P90 ADC, P25 and P10 FLAIR) were significant predictors of OS (log-rank p = 0.041 ADC; p=0.016 FLAIR). Median survival was 10.07 months for low and 28.17 months for high ADC, and 17.8 months for low and 8.0 months for high FLAIR. Post-treatment ADC (P90 and P75) and normalized PET uptake (mean, P90, and P75) were significant predictors of OS (p=0.037 ADC; p=0.047 PET); median survival was 10.07 months for low and 28.17 months for high ADC, and 28.7 months for low and 10.8 months for high PET uptake. Conclusion: Volumetric analysis of baseline and post treatment diffusion MRI predicts progression and survival in patients with high-grade gliomas receiving chemoradiation therapy. Post treatment F-18 FLT PET also predicts survival.