18F-FDOPA PET Predicts Good Prognosis as Soon as 2 Weeks After Start of Antiangiogenic Therapy in Recurrent High-Grade Glioma
In a study reported in Clinical Cancer Research, Schwarzenberg et al found 3,4-dihydroxy-6-[18F]-fluoro-L-phenylalanine (18F-FDOPA) positron-emission tomography (PET) metabolic tumor volume values at 2 weeks after the start of bevacizumab (Avastin) were highly predictive of outcome in patients with recurrent high-grade gliomas. 18F-FDOPA PET response differentiated poorer and better prognosis better than magnetic resonance imaging (MRI) response.
Study Details
In the study, 30 patients (18 male and 12 female, median age = 57.5 years, range = 26–78 years) underwent 18F-FDOPA PET scans for metabolic tumor volume and maximum and mean standardized uptake values immediately before and 2 and 6 weeks after the start of bevacizumab therapy and MRI scanning for response at 6 weeks. Patients had a histologically confirmed diagnosis of glioblastoma (n = 24) or anaplastic astrocytoma (n = 6) and had undergone surgical resection and chemoradiation, and all patients had MRI-confirmed recurrent disease. All but three patients also received irinotecan.
Changes in Metabolic Tumor Volume
Totals of 30, 28, and 24 18F-FDOPA PET scans at baseline, 2 weeks, and 6 weeks were available for analysis. Neither 18F-FDOPA PET standardized uptake values nor change in standardized uptake values during therapy were predictive of outcome. However, changes in and absolute values of metabolic tumor volume were predictive of outcome. At 2 weeks, there were 16 metabolic tumor volume responders and 12 nonresponders (−58% vs −15% change, P < .001); mean overall survival for these patients was 13.7 vs 7.0 months (P = .02). At 6 weeks, there were 17 metabolic tumor volume responders and 7 nonresponders (−67% vs +0.4% change, P = .01); mean overall survival was 14.1 vs 7.6 months (P = .02).
The metabolic tumor volume change at 6 weeks was a stronger predictor of overall survival (P < .001) than metabolic tumor volume change at 2 weeks (P = .001), whereas the metabolic tumor volume change at 2 weeks (P < .001) was a stronger predictor of progression-free survival (progression-free survival) than change at 6 weeks (P = .003).
Absolute Metabolic Tumor Volume Values
Assessment of absolute metabolic tumor volume values (using an optimal threshold value of metabolic tumor volume ≤ 18 mL) showed 17 responders and 11 nonresponders at 2 weeks; median overall survival was 12.1 vs 3.5 months (P < .001). Metabolic tumor volume at 2 weeks was found to be the most significant predictor of overall survival (P < .001) and progression-free survival (P = .001) on Kaplan-Meier analysis. Metabolic tumor volume value at 6 weeks was also significantly predictive of overall survival (P = .03) and progression-free survival (P = .02). By comparison, for the 22 MRI responders and 7 nonresponders at 6 weeks, median overall survival was 11.4 vs 7.7 months (P = .03).
The investigators concluded, “18F-FDOPA PET identifies treatment responders to antiangiogenic therapy as early as two weeks after treatment initiation.”
Wei Chen, MD, PhD, of University of California, Los Angeles, is the corresponding author for the Clinical Cancer Research article.
The study was supported by grants from the National Cancer Institute and National Institutes of Health/National Center for Advancing Translational Science. The study authors reported no potential conflicts of interest.
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