Background: Static [¹⁸F]-F-DOPA PET images are currently used for identifying patients with glioma recurrence/progression after treatment, although the additional diagnostic value of dynamic parameters remains unknown in this setting. The aim of this study was to evaluate the performances of static and dynamic [¹⁸F]-F-DOPA PET parameters for detecting patients with glioma recurrence/progression as well as assess further relationships with patient outcome.Methods: Fifty-one consecutive patients who underwent an [¹⁸F]-F-DOPA PET for a suspected glioma recurrence/progression at post-resection MRI, were retrospectively included. Static parameters, including mean and maximum tumor-to-normal-brain (TBR) ratios, tumor-to-striatum (TSR) ratios, and metabolic tumor volume (MTV), as well as dynamic parameters with time-to-peak (TTP) values and curve slope, were tested for predicting the following: (1) glioma recurrence/progression at 6 months after the PET exam and (2) survival on longer follow-up.Results: All static parameters were significant predictors of glioma recurrence/progression (accuracy ≥ 94%) with all parameters also associated with mean progression-free survival (PFS) in the overall population (allp< 0.001, 29.7 vs. 0.4 months for TBR_max, TSR_max, and MTV). The curve slope was the sole dynamic PET predictor of glioma recurrence/progression (accuracy = 76.5%) and was also associated with mean PFS (p< 0.001, 18.0 vs. 0.4 months). However, no additional information was provided relative to static parameters in multivariate analysis.Conclusion: Although patients with glioma recurrence/progression can be detected by both static and dynamic [¹⁸F]-F-DOPA PET parameters, most of this diagnostic information can be achieved by conventional static parameters.

This study evaluates the relevance of ¹⁸F-DOPA PET static and dynamic radiomics for differentiation of high-grade glioma (HGG) progression from treatment-related changes (TRC) by comparing diagnostic performances to the current PET imaging standard of care. Eighty-five patients with histologically confirmed HGG and investigated by dynamic ¹⁸F-FDOPA PET in two institutions were retrospectively selected. ElasticNet logistic regression, Random Forest and XGBoost machine models were trained with different sets of features—radiomics extracted from static tumor-to-background-ratio (TBR) parametric images, radiomics extracted from time-to-peak (TTP) parametric images, as well as combination of both—in order to discriminate glioma progression from TRC at 6 months from the PET scan. Diagnostic performances of the models were compared to a logistic regression model with TBR_mean ± clinical features used as reference. Training was performed on data from the first center, while external validation was performed on data from the second center. Best radiomics models showed only slightly better performances than the reference model (respective AUCs of 0.834 vs. 0.792, p < 0.001). Our current results show similar findings at the multicentric level using different machine learning models and report a marginal additional value for TBR static and TTP dynamic radiomics over the classical analysis based on TBR values.

The aim is to explore the concept of photopenic defects in newly diagnosed glioma patients with the 2 widely used ¹¹C-MET and ¹⁸F-FDOPA PET amino acid tracers. Thirty-two ¹¹C-MET and 26 ¹⁸F-FDOPA PET scans with amino acid PET-negative gliomas were selected in this European multicentric study. Of these gliomas, 16 ¹¹C-MET and 10 ¹⁸F-FDOPA PET scans with photopenic defects were identified, exhibiting lower mean tumor-to-background ratio as compared with isometabolic gliomas (P < 0.001). Gliomas with photopenic defects had no different progression-free survival than isometabolic gliomas in the whole population (P = 0.40), but shorter progression-free survival in the subgroup of World Health Organization grade II IDH-mutant astrocytomas (35 vs 68 months; P = 0.047).

Purpose: This study aimed to determine the impact of carbidopa premedication on static, dynamic and radiomics parameters of ¹⁸F-FDOPA PET in brain tumors. Methods: The study included 54 patients, 18 of whom received carbidopa, who underwent ¹⁸F-FDOPA PET for newly diagnosed gliomas. SUV-derived, 105 radiomics features and TTP dynamic parameters were extracted from volumes of interest in healthy brains and tumors. Simulation of the effects of carbidopa on time-activity curves were generated. Results: All static and TTP dynamic parameters were significantly higher in healthy brain regions of premedicated patients (ΔSUV_mean = +53%, ΔTTP = +48%, p < 0.001). Furthermore, carbidopa impacted 81% of radiomics features, of which 92% correlated with SUV_mean (absolute correlation coefficient ≥ 0.4). In tumors, premedication with carbidopa was an independent predictor of SUV_mean (ΔSUV_mean = +52%, p < 0.001) and TTP (ΔTTP = +24%, p = 0.025). All parameters were no longer significantly modified by carbidopa premedication when using ratios to healthy brain. Simulated data confirmed that carbidopa leads to higher tumor TTP values, corrected by the ratios. Conclusion: In ¹⁸F-FDOPA PET, carbidopa induces similarly higher SUV and TTP dynamic parameters and similarly impacts SUV-dependent radiomics in healthy brain and tumor regions, which is compensated for by correcting for the tumor-to-healthy-brain ratio. This is a significant advantage for multicentric study harmonization.

With great interest we read the editorial by Kamson entitled “Hypometabolic Gliomas on FET-PET—Is There an Inverted U-Curve for Survival?” in Neuro-Oncology¹ referring to our publication regarding the clinical relevance of photopenic defects on O-(2-[¹⁸F]fluoroethyl)-L-tyrosine (FET) PET in glioma patients.² In that paper, we identified within 100 patients with FET-PET–negative gliomas a subgroup of patients who even exhibit photopenic defects and had, moreover, an unfavorable outcome compared with gliomas with indifferent FET uptake (isometabolic gliomas). From our point of view, the frequency of photopenic defects is even lower than 10% (ie, ~5%). In his editorial, the author raised valuable new thoughts and ideas that are worth discussing.