Comparison of visual and semiquantitative analysis of 18F-FDOPA-PET/CT for recurrence detection in glioblastoma patients

Abstract

Background: Amino acid transport imaging with 18F-FDOPA PET is increasingly used for detection of glioblastoma recurrence. However, a standardized image interpretation for 18F-FDOPA brain PET studies has not yet been established. This study compares visual and semiquantitative analysis parameters for detection of tumor recurrence and correlates them with progression-free survival (PFS).

Methods: One-hundred ten patients (72 male:38 female) with suspected tumor recurrence who underwent 18F-FDOPA PET imaging were studied. PET scans were analyzed visually (5-point scale) and semiquantitatively (lesion-to-striatum- and lesion- to-normal-brain-tissue ratios using both SUV(mean) and SUV(max)). Accuracies for recurrence detection were calculated using histopathology and clinical follow-up for validation. Receiving operator characteristic and Kaplan-Meier survival analysis were performed to derive imaging-based prediction of PFS and overall survival (OS).

Results: Accuracies for detection of glioblastoma recurrence were similar for visual (82%) and semiquantitative (range, 77%-82%) analysis. Both visual and semiquantitative indices were significant predictors of PFS, with mean lesion-to normal brain tissue ratios providing the best discriminator (mean survival, 39.4 vs 9.3 months; P < .001). None of the investigated parameters was predictive for OS.

Conclusions: Both visual and semiquantitative indices detected glioblastoma recurrence with high accuracy and were predictive for PFS. Lesion-to-normal-tissue ratios were the best discriminators of PFS; however, none of the investigated parameters predicted OS. These retrospectively established analysis parameters need to be confirmed prospectively.

Keywords: 18F-FDOPA; glioblastoma; recurrence detection.

Fig. 1.

Axial views of PET and corresponding MRI images of 5 patients with suspected glioblastoma recurrences. Examples represent each of the 5 scoring options (2 = lesion uptake much greater than striatal uptake; 1 = lesion uptake greater than striatal uptake; 0 = lesion and striatal uptake appears isointense; −1 = lesion visible but < than striatal uptake; −2 = lesion nonvisible on PET). (A) ¹⁸F-DOPA-PET and MRI images of a 62-year-old male. FDOPA uptake was scored as 2. Lesion /striatum and lesion/normal brain SUV_mean ratios were 1.92 and 3.51, respectively. Recurrence was confirmed by histopathology, and the patient died within 3 months of the PET study. (B) ¹⁸F-DOPA-PET and MRI images of a 50-year-old male. FDOPA uptake was rated as 1. Lesion/striatum and lesion/normal brain SUV_mean ratios were 1.30 and 2.78, respectively. Histopathological verification was not available, and the patient died within 7 months of PET scan. (C) ¹⁸F-DOPA-PET and MRI images of a 47-year-old male. FDOPA uptake was rated as 0. Lesion/striatum and lesion/normal brain SUV_mean ratios were 0.94 and 1.53, respectively. Recurrence was confirmed by histopathology, and the patient died within 9 months of PET scan. D: ¹⁸F-DOPA-PET and MRI images of a 72-year-old male. FDOPA uptake was scored as -1. Lesion/striatum and lesion/normal brain SUV_mean ratios were 0.87 and 1.47, respectively Subsequent histopathology revealed necrosis; the patient died 12 months after the PET scan. E: ¹⁸F-DOPA-PET and MRI images of a 41-year-old male. FDOPA uptake was scored as -2. Lesion/striatum and lesion/normal brain SUV_mean ratios were 0.75 and 1.32, respectively. Histopathological verification was not available; the patient was alive 15 months after the PET scan.

Fig. 2.

ROC analysis of semiquantitative and visual parameters for prediction of (A) progression-free survival and (B) overall survival.

Fig. 3.

Kaplan Meier survival analysis plots for prediction of progression-free survival using (A) visual scale, and (B) mean lesion-to-normal brain ratios as discriminators. Corresponding log-rank test P values are P < .001 for both, respectively.