18F-FAZA PET/CT in pretreatment assessment of hypoxic status in high-grade glioma: correlation with hypoxia immunohistochemical biomarkers.

BACKGROUND: To investigate the correlation between 18F-labeled fluoroazomycinarabinoside (18F-FAZA) PET data and hypoxia immunohistochemical markers in patients with high-grade glioma (HGG). PATIENTS AND METHODS: Prospective study including 20 patients with brain MRI suggestive for HGG and undergoing 18F-FAZA PET/CT before treatment for hypoxia assessment. For each 18F-FAZA PET scan SUVmax, SUVmean and 18F-FAZA tumour volume (FTV) at 40, 50 and 60% threshold of SUVmax were calculated; hypoxic volume was estimated by applying different thresholds (1.2, 1.3 and 1.4) to tumour/blood ratio. Seventeen patients were analysed. The immunohistochemical analysis assessed the following parameters: hypoxia-inducible factor 1α, carbonic anhydrase IX (CA-IX), glucose transporter-1, tumour vascularity and Ki-67. RESULTS: 18F-FAZA PET showed a single lesion in 15/17 patients and multiple lesions in 2/17 patients. Twelve/17 patients had grade IV glioma and 5/17 with grade III glioma. Bioptic and surgical samples have been analysed separately. In the surgical subgroup (n = 7) a positive correlation was observed between CA-IX and SUVmax (P = 0.0002), SUVmean40 (P = 0.0058), SUVmean50 (P = 0.009), SUVmean60 (P = 0.0153), FTV-40-50-60 (P = 0.0424) and hypoxic volume1.2-1.3-1.4 (P = 0.0058). In the bioptic group (n = 10) tumour vascularisation was inversely correlated with SUVmax (P = 0.0094), SUVmean40 (P = 0.0107), SUVmean50 (P = 0.0094) and SUVmean60 (P = 0.0154). CONCLUSIONS: The correlation of 18F-FAZA PET parameters with CD31 and CA-IX represents a reliable method for assessing tumour hypoxia in HGG. The inverse correlation between tumour vascularisation, SUVmax and SUVmean suggest that highly vascularized tumours might present more oxygen supply than hypoxia.

Dual tracer 68Ga-DOTATOC and 18F-FDG PET/computed tomography radiomics in pancreatic neuroendocrine neoplasms: an endearing tool for preoperative risk assessment.

AIM: To explore the potentiality of radiomics analysis, performed on Ga-DOTATOC and fluorine-18-fluorodeoxyglucose (F-FDG) PET/computed tomography (CT) images, in predicting tumour aggressiveness and outcome in patients candidate to surgery for pancreatic neuroendocrine neoplasms (PanNENs). PATIENTS AND METHODS: Retrospective study including 61 patients who underwent Ga-DOTATOC and F-FDG PET/CT before surgery for PanNEN. Semiquantitative variables [SUVmax and somatostatin receptor density (SRD) for Ga-DOTATOC PET; SUVmax and MTV for F-FDG PET] and texture features [intensity variability, size zone variability (SZV), zone percentage, entropy; homogeneity, dissimilarity and coefficient of variation (Co-V)] have been analysed to evaluate their possible role in predicting tumour characteristics. Principal component analysis (PCA) was firstly performed and then multiple regression analyses were performed by using the extracted principal components. RESULTS: Regarding Ga-DOTATOC PET, SZV, entropy, intensity variability and SRD were predictive for tumour dimension. Regarding F-FDG PET, intensity variability, SZV, homogeneity, SUVmax and MTV were predictive for tumour dimension. Four principal components were extracted from PCA: PC1 correlated with all F-FDG variables, while PC2, PC3 and PC4 with Ga-DOTATOC variables. PC1 was the only significantly predicting angioinvasion (P = 0.0222); PC4 was the only one significantly predicting lymph nodal involvement (P = 0.0151). All principal components except PC4 significantly predicted tumour dimension (P <0.0001 for PC1, P = 0.0016 for PC2 and P < 0.0001 for PC3). Co-V from Ga-DOTATOC PET/CT was predictive of the outcome. CONCLUSION: Specific texture features derived from preoperative Ga-DOTATOC and F-FDG PET/CT could noninvasively predict specific tumour characteristics and patients' outcome, delineating the potential role of dual tracer technique and texture analysis in the risk assessment of patients with PanNENs.

Renal Function Assessment Gap in Clinical Practice: An Awkward Truth.

INTRODUCTION: An accurate assessment of renal function is needed in the majority of clinical settings. Unfortunately, the most used estimated glomerular filtration rate (eGFR) formulas are affected by significant errors in comparison to gold standards methods of measured GFR (mGFR). OBJECTIVE: The objective of the study is to determine the extent of the error of eGFR formulas compared to the mGFR in different specific clinical settings. METHODS: A total retrospectively consecutive cohort of 1,320 patients (pts) enrolled in 2 different European Hospitals (Center 1: 470 pts; Center 2: 850 pts) was collected in order to compare the most common eGFR formulas used by physicians with the most widespread mGFR methods in daily clinical practice (Iohexol Plasma Clearance -Center 1 [mGFR-iox] and Renal Scintigraphy -Center 2 [mGFR-scnt]). The study cohort was composed by urological, oncological, and nephrological pts. The agreement between eGFR and mGFR was evaluated using bias (as median of difference), precision (as interquartile range of difference) accuracy (as P30), and total deviation index. RESULTS: The most accurate eGFR formula in the comparison with gold standard method (Iohexol plasma clearance) in Center 1 was represented by s-creatinine and cystatin C combined Chronic Kidney Disease-Epidemiology Collaboration-cr-cy, even though the P30 is reduced (84%) under the threshold of 60 mL/min/1.73 m2. Similar results were found in Center 2, with a wider discrepancy between mGFR-scnt and eGFR formulas due to the minor accuracy of the nuclear tool in respect to the mGFR-iox. CONCLUSIONS: The loss of accuracy observed for the formulas at lower values of GFR suggests the mandatory use of gold standards methods as Iohexol Plasma Clearance to assess the correct status of renal function for critical cases. The center 2 showed lower levels of agreement between mGFR and eGFR suggesting that the errors are partially accounted for the Renal Scintigraphy technique too. In particular, we suggest the use of mGFR-iox in oncological urological and nephrological pts with an eGFR lower than 60 mL/min/1.73 m2.

18F-FDG PET/CT for Early Postradiotherapy Assessment in Solitary Bone Plasmacytomas.

PURPOSE: The purpose of this study was to evaluate the performance and possible prognostic value of early (18)F-FDG PET/CT (FDG PET/CT) assessment after radiotherapy (RT) in patients with solitary bone plasmacytoma (SBP). METHODS: Twenty-one patients affected by SBP who underwent FDG PET/CT scan for early restaging (≤6 months) postradiotherapy assessment were selected from the PET databases of University College London Hospital of London and San Raffaele Hospital of Milan. Patients with no abnormal uptake were classified as having no pathologic uptake (NPU). A SUV(max) cutoff value of 4 was chosen to discriminate minimal residual uptake (MRU; SUV(max) ≤ 4) from pathologic uptake (PU, SUV(max) >4). Progression-free survival (PFS) rate was estimated using Kaplan-Meier curves and Cox regression analysis. RESULTS: In 10 of 21 patients restaged by FDG PET/CT, further previous baseline scan was available also at staging, and results showed positive findings at the level of all biopsy-proven disease areas.Considering MRU as PU, FDG PET/CT showed a sensitivity and specificity of 86% and 29%, respectively. Using SUV(max) >4 as the cutoff, sensitivity and specificity were 86% and 93%, respectively. Kaplan-Meier curves revealed a significant difference in PFS probability between patients classified as positive on FDG PET/CT using a cutoff of SUV(max) >4 (PU) and those classified as negative (NPU + MRU) (log-rank, Mantel-Cox, P = 0.009; χ(2) = 6.85). Cox regression analysis of PFS using SUV(max) >4 as cutoff revealed an interesting relation in prediction of progression (HR, 9.458). CONCLUSION: (18)F-FDG PET/CT for early restaging after RT in patients with SBP should be considered carefully in view of the lack of specificity of a low SUV(max) value. The good correlation between a high SUV(max) value and follow-up suggests a possible prognostic role for FDG PET/CT in disease progression at early restaging after RT.

PET/CT and breast cancer.

During the past decade, the application of positron emission tomography with [(18)F]fluoro-2-deoxy-D-glucose (FDG-PET) has remarkably improved the management of cancer patients. Nevertheless, the clinical interpretation of FDG-PET scan can be difficult for two main reasons: (1) anatomical localisation of FDG uptake is not easy, (2) normal physiological accumulation of FDG can be misinterpreted as a pathologic area. It has been demonstrated that the visual correlation of PET with morphological procedures, such as computed tomography or magnetic resonance imaging, can improve the accuracy of PET alone. However, the time interval between the two scans, the time employed by the operator and difficulties in co-registering imaging of the abdomen and pelvis make the co-registration of separately obtained images clinically difficult. A novel combined PET/CT system has been built that improves the capacity to correctly localise and interpret FDG uptake. To date only a few studies have been conducted on the potential role of PET/CT in the management of breast cancer patients, but the better performance of this technique compared with PET alone should also be relevant for breast cancer application. In this review, we evaluate the possible impact on breast cancer diagnosis of PET/CT compared with PET alone, with respect to disease re-staging, treatment monitoring, preoperative staging and primary diagnosis. In addition, the possible role of PET/CT for radiotherapy planning is evaluated.