Assessment of Bone Metastases in Patients with Prostate Cancer-A Comparison between 99mTc-Bone-Scintigraphy and [68Ga]Ga-PSMA PET/CT.

PURPOSE: Bone scintigraphy is the standard of reference in bone metastases in prostate cancer patients. However, new radiotracers employed in prostate-specific membrane antigen (PSMA)-ligands has led to the growing importance of PET/CT as diagnostic tool. The aim of our study was to investigate the difference between bone scan and PSMA-PET/CT for the detection of bone metastases in prostate cancer. METHODS: Thirty patients with bone metastases originating from prostate cancer were examined by 99mTc-MDP bone scan and 68Ga-PSMA-PET/CT within an average of 21 days. Bone scans were analyzed visually according to the number of lesions and using the software package ExiniBONE by Exini Diagnostics. PET/CT data was analyzed visually. Numbers of detected lesions were compared for the different methods for the whole patient and for different regions. In addition, results were compared to serum prostate-specific antigen (PSA), alkaline phosphatase (ALP), bone alkaline phosphatase (bALP), pro gastrin releasing peptide (pGRP) and eastern cooperative oncology group (ECOG) performance status. RESULTS: In the bone scans, visual and semiautomatic lesion detection showed similar results with an average of 19.4 and 17.8 detected bone lesion per patient. However, in PSMA-PET/CT, on average double the numbers of lesions (40.0) were detected. The largest differences were found in the thorax and pelvis, which can be explained by the advantages of tomographic imaging. Bland-Altman analysis showed greater differences in patients with large numbers of bone metastases. CONCLUSION: No significant difference was found when using semiautomatic analysis compared to visual reading for bone scans. Fewer bone metastases were detected in bone scans than in PSMA-PET/CT. However, in none of our patients would the difference have led to clinical consequences. Therefore, it seems that for patients undergoing PSMA-PET/CT, there is no need to perform additional bone scans if the appropriate PET/CT protocols are applied.

Assessment of tumor heterogeneity in treatment-naïve adrenocortical cancer patients using (18)F-FDG positron emission tomography.

As an orphan malignancy, only limited treatment options are available in adrenocortical carcinoma (ACC). Non-invasive risk assessment has not been described but may be of value to stratify patients for treatment. We aimed to evaluate the potential value of intra-individual tumor heterogeneity as assessed by (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) for outcome prediction in treatment-naïve ACC patients. Ten patients with primary diagnosis of ACC were included in this study. Prior to any treatment initiation, baseline (18)F-FDG PET scans were performed. Tumor staging was performed using the European Network for the Study of Adrenal Tumors (ENS@T). Intratumoral heterogeneity of the primary tumor was assessed by manual segmentation using conventional PET parameters (standardized uptake values and tumor-to-liver ratios) and textural features. The impact of tumoral heterogeneity based on pre-therapeutic (18)F-FDG PET to predict progression-free (PFS) and overall survival (OS) was evaluated by receiver operating characteristic analysis. On average, tumor recurrence or progression was detected after median of 561 days (range 71-1434 days) after the pre-therapeutic baseline PET scan. 50 % of the patients died of ACC within the follow-up period (mean 983 ± 404 days). Pre-therapeutic tumor volume was associated with PFS (r = -0.67, p = 0.05) and Ki67 index with OS (r = -0.66, p = 0.04). ENS@T tumor stage was the only parameter to correlate with both PFS and OS (r = -0.82, p = 0.001, and r = -0.72, p = 0.01, respectively). In the subgroup of patients without distant metastases (ENS@T stages II and III), age and pre-therapeutic tumor volume correlated significantly with PFS (r = 0.96, p = 0.01 and r = -0.93, p = 0.02, respectively) and OS (r = 0.95, p = 0.02 and r = -0.90, p = 0.04, respectively). None of the investigated classic or textural PET parameters predicted PFS or OS. In this pilot study in treatment-naïve ACC patients, conventional (18)F-FDG PET-derived parameters and textural tumor heterogeneity features were not suitable to identify high-risk patients.

Textural Parameters of Tumor Heterogeneity in ¹8F-FDG PET/CT for Therapy Response Assessment and Prognosis in Patients with Locally Advanced Rectal Cancer.

UNLABELLED: (18)F-FDG PET/CT is effective in the assessment of therapy response. Changes in glucose uptake or tumor size are used as a measure. Tumor heterogeneity was found to be a promising predictive and prognostic factor. We investigated textural parameters for their predictive and prognostic capability in patients with rectal cancer using histopathology as the gold standard. In addition, a comparison to clinical outcome was performed. METHODS: Twenty-seven patients with rectal cancer underwent (18)F-FDG PET/CT before, 2 wk after the start, and 4 wk after the completion of neoadjuvant chemoradiotherapy. In all PET/CT scans, conventional parameters (tumor volume, diameter, maximum and mean standardized uptake values, and total lesion glycolysis [TLG]) and textural parameters (coefficient of variation [COV], skewness, and kurtosis) were determined to assess tumor heterogeneity. Values on pretherapeutic PET/CT as well as changes early in the course of therapy and after therapy were compared with histopathologic response. In addition, the prognostic value was assessed by correlation with time to progression and survival time. RESULTS: The COV showed a statistically significant capability to assess histopathologic response early in therapy (sensitivity, 68%; specificity, 88%) and after therapy (79% and 88%, respectively). Thereby, the COV had a higher area under the curve in receiver-operating-characteristic analysis than did any analyzed conventional parameter for early and late response assessment. The COV showed a statistically significant capability to evaluate disease progression and to predict survival, although the latter was not statistically significant. CONCLUSION: Tumor heterogeneity assessed by the COV, being superior to the investigated conventional parameters, is an important predictive factor in patients with rectal cancer. Furthermore, it can provide prognostic information. Therefore, its application is an important step for personalized treatment of rectal cancer.

Quantitative assessment of glucose metabolism in the vessel wall of abdominal aortic aneurysms: correlation with histology and role of partial volume correction.

Inflammatory-proteolytic processes in the vessel wall are essential in the pathophysiology of abdominal aortic aneurysm (AAA). It has been demonstrated that, (18)F-FDG-PET/CT may be useful for detection of pathological wall metabolism and therefore risk stratification. Quantification of the FDG-uptake in AAA wall is hampered by partial-volume (PV)-effects. For correction and accurate quantitative (18)F-FDG-uptake analysis we designed and validated a novel IDL-based software in correlation to phantom studies, histopathology and clinical presentation of AAA patients. For in vivo studies 23 patients with symptomatic and asymptomatic AAA underwent (18)F-FDG-PET/CT before surgery. In areas with (18)F-FDG-uptake the maximum and mean standardized uptake values in the vessel wall with (PVC-SUV(max), PVC-SUV(mean)) and without (SUV(max), SUV(mean)) PV-correction were determined. Results were correlated with clinical presentation, corresponding macrophage-infiltration and MMP-2- and -9-expression in surgical specimens. In patients, SUV(max), SUV(mean) as well as PVC-SUV(max) or PVC-SUV(mean) enabled a highly significant (p < 0.005) discrimination of symptomatic and asymptomatic AAA. Uncorrected and corrected SUVs showed comparable correlations with macrophage-infiltration and MMP-9 expression. No correlation of (18)F-FDG-uptake and MMP-2 was found. In vivo correlations of detected FDG-uptake with clinical and histological results showed comparable results for corrected and uncorrected SUVs. PV-correction is not mandatory for qualitative clinical assessment of glucose metabolism in the vessel wall of AAA-patients but may be necessary to establish quantitative cut off values to stratify patients for aneurysm repair.

Assessment of tumor volumes in skull base glomus tumors using Gluc-Lys[(18)F]-TOCA positron emission tomography.

PURPOSE: To assess a threshold for Gluc-Lys[(18)F]-TOCA positron emission tomography (PET) in target volume delineation of glomus tumors in the skull base and to compare with MRI-based target volume delineation. METHODS AND MATERIALS: The threshold for volume segmentation in the PET images was determined by a phantom study. Nine patients with a total of 11 glomus tumors underwent PET either with Gluc-Lys[(18)F]-TOCA or with (68)Ga-DOTATOC (in 1 case). All patients were additionally scanned by MRI. Positron emission tomography and MR images were transferred to a treatment-planning system; MR images were analyzed for lesion volume by two observers, and PET images were analyzed by a semiautomated thresholding algorithm. RESULTS: Our phantom study revealed that 32% of the maximum standardized uptake value is an appropriate threshold for tumor segmentation in PET-based target volume delineation of gross tumors. Target volume delineation by MRI was characterized by high interobserver variability. In contrast, interobserver variability was minimal if fused PET/MRI images were used. The gross tumor volumes (GTVs) determined by PET (GTV-PET) showed a statistically significant correlation with the GTVs determined by MRI (GTV-MRI) in primary tumors; in recurrent tumors higher differences were found. The mean GTV-MRI was significantly higher than mean GTV-PET. The increase added by MRI to the common volume was due to scar tissue with strong signal enhancement on MRI. CONCLUSIONS: In patients with glomus tumors, Gluc-Lys[(18)F]-TOCA PET helps to reduce interobserver variability if an appropriate threshold for tumor segmentation has been determined for institutional conditions. Especially in patients with recurrent tumors after surgery, Gluc-Lys[(18)F]-TOCA PET improves the accuracy of GTV delineation.