Veronika Dunkl

The use of dynamic O-(2-18F-fluoroethyl)-l-tyrosine PET in the diagnosis of patients with progressive and recurrent glioma

BACKGROUND We evaluated the diagnostic value of static and dynamic O-(2-[(18)F]fluoroethyl)-L-tyrosine ((18)F-FET) PET parameters in patients with progressive or recurrent glioma. METHODS We retrospectively analyzed 132 dynamic (18)F-FET PET and conventional MRI scans of 124 glioma patients (primary World Health Organization grade II, n = 55; grade III, n = 19; grade IV, n = 50; mean age, 52 ± 14 y). Patients had been referred for PET assessment with clinical signs and/or MRI findings suggestive of tumor progression or recurrence based on Response Assessment in Neuro-Oncology criteria. Maximum and mean tumor/brain ratios of (18)F-FET uptake were determined (20-40 min post-injection) as well as tracer uptake kinetics (ie, time to peak and patterns of the time-activity curves). Diagnoses were confirmed histologically (95%) or by clinical follow-up (5%). Diagnostic accuracies of PET and MR parameters for the detection of tumor progression or recurrence were evaluated by receiver operating characteristic analyses/chi-square test. RESULTS Tumor progression or recurrence could be diagnosed in 121 of 132 cases (92%). MRI and (18)F-FET PET findings were concordant in 84% and discordant in 16%. Compared with the diagnostic accuracy of conventional MRI to diagnose tumor progression or recurrence (85%), a higher accuracy (93%) was achieved by (18)F-FET PET when a mean tumor/brain ratio ≥2.0 or time to peak <45 min was present (sensitivity, 93%; specificity, 100%; accuracy, 93%; positive predictive value, 100%; P < .001). CONCLUSION Static and dynamic (18)F-FET PET parameters differentiate progressive or recurrent glioma from treatment-related nonneoplastic changes with higher accuracy than conventional MRI.

The Usefulness of Dynamic O-(2-18F-Fluoroethyl)-l-Tyrosine PET in the Clinical Evaluation of Brain Tumors in Children and Adolescents

Experience regarding O-(2-18F-fluoroethyl)-l-tyrosine (18F-FET) PET in children and adolescents with brain tumors is limited. Methods: Sixty-nine 18F-FET PET scans of 48 children and adolescents (median age, 13 y; range, 1–18 y) were analyzed retrospectively. Twenty-six scans to assess newly diagnosed cerebral lesions, 24 scans for diagnosing tumor progression or recurrence, 8 scans for monitoring of chemotherapy effects, and 11 scans for the detection of residual tumor after resection were obtained. Maximum and mean tumor-to-brain ratios (TBRs) were determined at 20–40 min after injection, and time–activity curves of 18F-FET uptake were assigned to 3 different patterns: constant increase; peak at greater than 20–40 min after injection, followed by a plateau; and early peak (≤20 min), followed by a constant descent. The diagnostic accuracy of 18F-FET PET was assessed by receiver-operating-characteristic curve analyses using histology or clinical course as a reference. Results: In patients with newly diagnosed cerebral lesions, the highest accuracy (77%) to detect neoplastic tissue (19/26 patients) was obtained when the maximum TBR was 1.7 or greater (area under the curve, 0.80 ± 0.09; sensitivity, 79%; specificity, 71%; positive predictive value, 88%; P = 0.02). For diagnosing tumor progression or recurrence, the highest accuracy (82%) was obtained when curve patterns 2 or 3 were present (area under the curve, 0.80 ± 0.11; sensitivity, 75%; specificity, 90%; positive predictive value, 90%; P = 0.02). During chemotherapy, a decrease of TBRs was associated with a stable clinical course, and in 2 patients PET detected residual tumor after presumably complete tumor resection. Conclusion: Our findings suggest that 18F-FET PET can add valuable information for clinical decision making in pediatric brain tumor patients.

Imaging of non-or very subtle contrast-enhancing malignant gliomas with [ 11C]-methionine positron emission tomography

In patients with World Health Organization (WHO) grade III glioma with a lack of or minimal (< 1 cm3) magnetic resonance imaging (MRI) contrast enhancement, the volume of the metabolically active part of the tumor was assessed by [ 11 C]-methionine positron emission tomography (MET-PET). Eleven patients with WHO grade III gliomas underwent MET-PET and MRI (contrast-enhanced T1-and T2-weighted images). To calculate the volumes in cubic centimeters, threshold-based volume of interest analyses of the metabolically active tumor (MET uptake index ≥ 1.3), contrast enhancement, and the T2 lesion were performed after coregistration of all images. In all patients, the metabolically active tumor volume was larger than the volume of gadolinium–diethylenetriamine pentaacetic acid (Gd-DTPA) enhancement (20.8 ± 18.8 vs 0.29 ± 0.25 cm3; p < .001). With the exception of one patient, the volumes of contrast enhancement were located within the metabolically active tumor volume. In contrast, in the majority of patients, MET uptake overlapped with the T2 lesion and reached beyond it (in 10 of 12 MRIs/MET-PET scans). The present data suggest that in patients with WHO grade III glioma with minimal or a lack of contrast enhancement, MET-PET delineates metabolically active tumor tissue. These findings support the use of combined PET-MRI with radiolabeled amino acids (eg, MET) for the delineating of the true extent of active tumor in the diagnosis and treatment planning of patients with gliomas.

Volumetry of [¹¹C]-methionine positron emission tomographic uptake as a prognostic marker before treatment of patients with malignant glioma.

The purpose of this positron emission tomography (PET) study was to compare the prognostic value of pretreatment volume of [11C] methionine (MET) uptake and semiquantitative MET uptake ratio in patients with malignant glioma. The study population comprised 40 patients with malignant glioma. Pretreatment magnetic resonance imaging (MRI) and MET-PET imaging were performed before the initiation of glioma treatment in all patients. The pretreatment MET uptake ratios and volumes were assessed. To create prognostically homogeneous subgroups, patients′ pretreatment prognostic factors were stratified according to the six classes of Radiation Therapy Oncology Group recursive partitioning analysis (RTOG RPA). Univariate and multivariate analyses were performed to determine significant prognostic factors. Survival analyses identified the pretreatment volume of MET uptake and a higher RTOG RPA class as significant predictors. In contrast, pretreatment maximum areas of contrast enhancement on MRI and semiquantitative MET uptake ratios could not be identified as significant prognostic factors. The patients′ outcomes and Karnofsky Performance Scale scores were significantly correlated with pretreatment volume of MET uptake but not with semiquantitative MET uptake ratio. The data suggest that pretreatment volumetry of MET uptake but not the semiquantitative MET uptake ratio is a useful biologic prognostic marker in patients with malignant glioma.

Earlier Diagnosis of Progressive Disease during Bevacizumab Treatment Using O-(2-18F-Fluorethyl)-L-Tyrosine Positron Emission Tomography in Comparison with Magnetic Resonance Imaging

Antiangiogenic treatment using bevacizumab in brain tumor patients may cause difficulties in the diagnosis of tumor progression (ie, nonenhancing tumor progression). Newly defined criteria for treatment assessment and diagnosis of tumor progression (ie, RANO [Response Assessment in Neuro-Oncology] criteria) have implemented signal alterations on T2/fluid-attenuated inversion recovery (FLAIR) sequences to changes in contrast enhancement. However, T2/FLAIR hyperintensity may be influenced by other causes (eg, radiation-induced leukoencephalopathy, peritumoral edema, gliosis). Positron emission tomography using the radiolabeled amino acid O-(2-[18F]fluoroethyl)-L-tyrosine (18F-FET-PET) may help detect the metabolically active tumor extent. We present 18F-FET-PET imaging findings in a glioblastoma patient during bevacizumab treatment suggesting an earlier diagnosis of tumor progression than magnetic resonance imaging changes, which are based on the RANO criteria.

Clinical routine assessment of palliative care symptoms and concerns and caregiver burden in glioblastoma patients: an explorative field study

The implementation of self-reported outcome measurements into clinical routine was tested to help facilitate early access to palliative care (PC) for glioblastoma (GBM)-patients. Measures detail PC symptoms and concerns and caregiver burden. Between January 2014 and December 2016, a total of 337 GBM-patients were discussed during meetings of the neuro-oncology tumor board to examine further treatment options. Each patient, along with their caregivers, was requested to participate in self-assessment using the palliative outcome scale (POS) and the Zarit Burden Interview (ZBI). Analyses encompassed summary statistics, non-parametric tests, visual graphic analysis, content analysis and assessing the utilization of the specialized PC consulting service (SPCCS). Ninety-five (28%) GBM-patients and 71 (21%) caregivers completed the self-assessment. Of these, 20 patients and 12 caregivers repeated the assessment at least once more during follow-up. POS total scores were similar in the group of patients with initial diagnosis [10 (0–31)] and those with later disease stages like recurrent diagnosis [9 (0–25)], but ZBI total scores differed [14 (0–51) vs. 24 (2–62)]. Single item analysis demonstrated that anxiety and worries about the future predominated. Caregivers were torn between high engagement in caring and feeling overburdened. Still, requests for the SPCCS showed no increase. Actual implementation of measures like POS and ZBI for detecting PC concerns and caregiver burden with GBM-patients in the field remains challenging as indicated by the limited response rate and lack of increased requests for the SPCCS. Modified clinical routines including strengthening awareness of PC, and allowing proxy-assessment might help to overcome barriers.

The use of O -(2- 18 F-fluoroethyl)-L-tyrosine PET in the diagnosis of gliomas located in the brainstem and spinal cord

Background Despite an increasing number of O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) PET studies in supratentorial gliomas, studies regarding the usefulness of 18F-FET PET in brainstem and spinal cord gliomas to date remain scarce. Methods Thirty-six 18F-FET PET scans were performed in 29 patients with brainstem (n = 29 scans) or spinal cord glioma (n = 7 scans). In 32 of 36 PET scans, a dynamic acquisition was performed. Fifteen scans in 15 patients were performed to assess newly diagnosed lesions, and 21 scans were obtained during follow-up: for diagnosing tumor progression (n = 15 scans in 14 patients) as well as for treatment monitoring (n = 6 scans in 3 patients). Four patients underwent additional serial scans (range, 1-2), and 3 of these 4 patients were examined for more than one indication. Maximum and mean tumor/brain ratios (TBRmax/mean) of 18F-FET uptake (20-40 min post injection) as well as kinetic 18F-FET uptake parameters were determined. Final diagnoses were confirmed histologically (54%) or by clinical follow-up (46%). Results In all newly diagnosed high-grade (n = 3 patients) and in 5 of 11 patients with low-grade gliomas, 18F-FET uptake was increased (TBRmax ≥2.5 and/or TBRmean ≥1.9). In 2 patients with newly diagnosed gliomas without MR contrast enhancement, 18F-FET PET nevertheless showed increased metabolism. At suspected progression, the combination of TBRs with kinetic 18F-FET parameters correctly identified presence or absence of progressive disease in 9 of 11 patients (82%). Conclusions This preliminary study suggests that 18F-FET PET adds valuable diagnostic information in brainstem and spinal cord glioma, particularly when the diagnostic information derived from MRI is equivocal.

Predicting IDH genotype in gliomas using FET PET radiomics

Mutations in the isocitrate dehydrogenase (IDH mut) gene have gained paramount importance for the prognosis of glioma patients. To date, reliable techniques for a preoperative evaluation of IDH genotype remain scarce. Therefore, we investigated the potential of O-(2-[18F]fluoroethyl)-L-tyrosine (FET) PET radiomics using textural features combined with static and dynamic parameters of FET uptake for noninvasive prediction of IDH genotype. Prior to surgery, 84 patients with newly diagnosed and untreated gliomas underwent FET PET using a standard scanner (15 of 56 patients with IDH mut) or a dedicated high-resolution hybrid PET/MR scanner (11 of 28 patients with IDH mut). Static, dynamic and textural parameters of FET uptake in the tumor area were evaluated. Diagnostic accuracy of the parameters was evaluated using the neuropathological result as reference. Additionally, FET PET and textural parameters were combined to further increase the diagnostic accuracy. The resulting models were validated using cross-validation. Independent of scanner type, the combination of standard PET parameters with textural features increased significantly diagnostic accuracy. The highest diagnostic accuracy of 93% for prediction of IDH genotype was achieved with the hybrid PET/MR scanner. Our findings suggest that the combination of conventional FET PET parameters with textural features provides important diagnostic information for the non-invasive prediction of the IDH genotype.

Dabrafenib Treatment in a Patient with an Epithelioid Glioblastoma and BRAF V600E Mutation

Novel therapeutic targets in malignant glioma patients are urgently needed. Point mutations of the v-Raf murine sarcoma viral oncogene homolog B (BRAF) gene occur predominantly in melanoma patients, but may also occur in gliomas. Thus, this is a target of great interest for this group of patients. In a nine-year-old male patient, an anaplastic astrocytoma in the left temporoparietal region was diagnosed histologically. After first- and second-line treatment, a malignant progression to a secondary glioblastoma was observed ten years after the initial diagnosis. Within the following seven years, all other conventional treatment options were exhausted. At this time point, recurrent tumor histology revealed an epithelioid glioblastoma, without a mutation in the isocitrate dehydrogenase gene (IDH wild-type). In order to identify a potential target for an experimental salvage therapy, mutational tumor analysis showed a BRAF V600E mutation. Consecutively, dabrafenib treatment was initiated. The patient remained clinically stable, and follow-up magnetic resonance images (MRI) were consistent with “Stable Disease” according to the Response Assessment in Neuro-Oncology Working Group (RANO) criteria for the following ten months until tumor progression was detected. The patient died 16 months after dabrafenib treatment initiation. Particularly in younger glioma patients as well as in patients with an epithelioid glioblastoma, screening for a V600E BRAF mutation is promising since, in these cases, targeted therapy with BRAF inhibitors seems to be a useful salvage treatment option.

NIMG-28TREATMENT RESPONSE EVALUATION USING FET PET COMPARED TO STANDARD MRI IN GLIOBLASTOMA PATIENTS AT FIRST RECURRENCE TREATED WITH BEVACIZUMAB PLUS LOMUSTINE

BACKGROUND: We compared prospectively MRI response assessment based on RANO criteria with metabolic O-(2-18F-fluoroethyl)-L-tyrosine (FET) PET response evaluation during bevacizumab plus lomustine (BEV/LOM) treatment in glioblastoma patients at first recurrence. METHODS: Patients at first recurrence of a primary glioblastoma after radiotherapy with concomitant and adjuvant temozolomide chemotherapy were treated accordingly to the BELOB trial with LOM 90 mg/m2 every 6 weeks and BEV 10 mg/kg every 2 weeks. Dynamic FET PET and standard MRI scans were performed at baseline and after 8-10 weeks. FET PET metabolic tumor volumes (MTV), maximum and mean tumor/brain ratios (TBRmax/mean) as well as dynamic FET PET parameters were obtained. The predictive ability of FET PET parameters and standard MRI on treatment response assessment was evaluated with regard to PFS and OS after starting of treatment. Using receiver-operating characteristic curve analyses, threshold values for FET PET parameter changes were obtained. MRI changes consistent with “Stable Disease”, “Partial Response” and “Complete Response” were considered as treatment response. Subsequently, Kaplan-Meier survival analyses were performed to assess their predictive power for survival. RESULTS: Nineteen patients were included. Fifteen of 19 patients (age range, 34-75 years; MGMT promoter not methylated, 87%; IDH wild type, 100%) were eligible for data evaluation. Treatment response as assessed by standard MRI based on RANO criteria was not predictive for a significant longer PFS (P = 0.23) and OS (P = 0.07), respectively. In contrast, FET PET changes predicted a longer PFS (MTV decrease > 25%, P = 0.01; TBRmax decrease > 12%, P = 0.02) and OS (MTV decrease > 10%, P = 0.04), respectively. Interestingly, absolute MTV at the first follow-up scan provides the most significant prediction for increased PFS (P = 0.006) as well as OS (P = 0.003). However, both TBRmean and dynamic FET PET parameters were not predictive for treatment response. CONCLUSIONS: FET PET appears to be helpful to identify treatment responders to BEV/LOM early after initiation of treatment.