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The myocardial oxygen consumption (MVo2) depends on left ventricular (LV) systolic pressure-volume area in normal humans. Infusion of a catecholamine, dobutamine, increases the energy utilization at similar levels of workload, resulting in a conspicuous O2-wasting effect and decrease in contraction efficiency. Positron emission tomography and two dimensional echocardiography assess MVO2 levels and LV mechanics, respectively.

Background:PET-guided dose painting (DP) aims to target radioresistant tumour regions in order to improve radiotherapy (RT) outcome. Besides the well-known [18F]fluorodeoxyglucose (FDG), the hypoxia positron emission tomography (PET) tracer [18F]fluoroazomycin arabinoside (FAZA) could provide further useful information to guide the radiation dose prescription. In this study, we compare the spatial distributions of FDG and FAZA PET uptakes in lung tumours. Material and methods:Fourteen patients with unresectable lung cancer underwent FDG and FAZA 4D-PET/CT on consecutive days at three time-points: prior to RT (pre), and during the second (w2), and the third (w3) weeks of RT. All PET/CT were reconstructed in their time-averaged midposition (MidP). The metabolic tumour volume (MTV: FDG standardised uptake value (SUV) > 50% SUVmax), and the hypoxic volume (HV: FAZA SUV > 1.4) were delineated within the gross tumour volume (GTVCT). FDG and FAZA intratumoral PET uptake distributions were subsequently pairwise compared, using both volume-, and voxel-based analyses. Results:Volume-based analysis showed large overlap between MTV and HV: median overlapping fraction was 0.90, 0.94 and 0.94, at the pre, w2 and w3 time-points, respectively. Voxel-wise analysis between FDG and FAZA intratumoral PET uptake distributions showed high correlation: median Spearman’s rank correlation coefficient was 0.76, 0.77 and 0.76, at the pre, w2 and w3 time-points, respectively. Interestingly, tumours with high FAZA uptake tended to show more similarity between FDG and FAZA intratumoral uptake distributions than those with low FAZA uptake. Conclusions:In unresectable lung carcinomas, FDG and FAZA PET uptake distributions displayed unexpectedly strong similarity, despite the distinct pathways targeted by these tracers. Hypoxia PET with FAZA brought very little added value over FDG from the perspective of DP in this population. [ABSTRACT FROM PUBLISHER]

Herein the synthesis of various SCF218F-containing derivatives is reported by a transition metal-free process. By using HCF218F, readily generated from a bench-stable difluoromethyl sulfonium salt, various aromatic disulfides were easily converted into the desired radiolabelled trifluoromethylthiolated compounds in the presence of a base. This protocol allowed the formation of the SCF218F-containing aromatic derivatives in good to excellent radiochemical yields. This process was also extended to the corresponding selenium derivative. [ABSTRACT FROM AUTHOR]

Background:Dose painting (DP) aims to improve radiation therapy (RT) outcome by targeting radioresistant tumour regions identified through functional imaging, e.g., positron emission tomography (PET). Importantly, the expected benefit of DP relies on the ability of PET imaging to identify tumour areas which could be consistently targeted throughout the treatment. In this study, we analysed the spatial stability of two potential DP targets in lung cancer patients undergoing RT: the tumour burden surrogate [18F]fluorodeoxyglucose (FDG) and the hypoxia surrogate [18F]fluoroazomycin arabinoside (FAZA). Materials and methods:Thirteen patients with unresectable lung tumours underwent FDG and FAZA 4D-PET/CT before (pre), and during the second (w2) and third (w3) weeks of RT. All PET/CT were reconstructed in their time-averaged midposition (MidP) for further analysis. The metabolic tumour volume (MTV: FDG standardised uptake value (SUV) > 50% SUVmax) and the hypoxic volume (HV: FAZA SUV >1.4) were delineated within the gross tumour volume (GTVCT). The stability of FDG and FAZA PET uptake distributions during RT was subsequently assessed through volume-overlap analysis and voxel-based correlation analysis. Results:The volume-overlap analysis yielded median overlapping fraction (OF) of 0.86 between MTVpreand MTVw2and 0.82 between MTVpreand MTVw3. In patients with a detectable HV, median OF was 0.82 between HVpreand HVw2and 0.90 between HVpreand HVw3. The voxel-based correlation analysis yielded median Spearman’s correlation coefficient (rS) of 0.87 between FDGpreand FDGw2and 0.83 between FDGpreand FDGw3. Median rSwas 0.78 between FAZApreand FAZAw2and 0.79 between FAZApreand FAZAw3. Conclusions:FDG and FAZA PET uptake distributions were spatially stable during the 3 first weeks of RT in patients with unresectable lung cancer, both based on volume- and voxel-based indicators. This might allow for a consistent targeting of high FDG or FAZA PET uptake regions as part of a DP strategy. [ABSTRACT FROM AUTHOR]

Early markers of treatment response may help in the management of patients by predicting the outcome of a specific therapeutic intervention. Here, we studied the potential value of diffusion-weighted MRI (DW-MRI) and 18F-fluorothymidine (18F-FLT), markers of cell death and cell proliferation respectively, to predict the response to irradiation. In addition, dose escalation and/or carbogen breathing were used to modulate the response to irradiation. The studies were performed on two hypoxic rat tumor models: rhabdomyosarcoma and 9L-glioma. The rats were imaged using MRI and PET before and two days after the treatment. In both tumor models, changes in ADC (apparent diffusion coefficient) and 18F-FLT SUV (standardized uptake value) were significantly correlated with the tumor growth delay. For both tumor models, the ADC values increased in all irradiated groups two days after the treatment while they decreased in the untreated groups. At the same time, the uptake of 18F-FLT increased in the untreated groups and decreased in all treated groups. Yet, ADC values were not sensitive enough to predict the added value of dose escalation or carbogen breathing in either model. Change in 18F-FLT uptake was able to predict the higher tumor response when using increased dose of irradiation, but not when using a carbogen breathing challenge. Our results also emphasize that the magnitude of change in 18F-FLT uptake was strongly dependent on the tumor model. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Background. The Warburg phenotype identified decades ago describes tumor cells with increased glycolysis and decreased mitochondrial respiration even in the presence of oxygen. This particular metabolism also termed 'aerobic glycolysis' reflects an adaptation of tumor cells to proliferation in a heterogeneous tumor microenvironment. Although metabolic alterations in cancer cells are common features, their impact on the response to radiotherapy is not yet fully elucidated. This study investigated the impact of cellular oxygen consumption inhibition on the tumor response to radiotherapy. Material and methods. Warburg-phenotype tumor cells with impaired mitochondrial respiration (MD) were produced and compared in respect to their metabolism to the genetically matched parental cells (WT). After characterization of their metabolism we compared the response of MD cells to irradiation in vivo and in vitro to the genetically matched parental cells (WT). Results. We first confirmed that MD cells were exclusively glycolytic while WT cells exhibited mitochondrial respiration. We then used these cells for assessing the response of WT and MD tumors to a single dose of radiation and showed that the in vivo tumor growth delay of the MD group was increased, indicating an increased radiosensitivity compared to WT while the in vitro ability of both cell lines to repair radiation-induced DNA damage was similar. Conclusion. Taken together, these results indicate that in addition to intrinsic radiosensitivity parameters the tumor response to radiation will also depend on their metabolic rate of oxygen consumption. [ABSTRACT FROM AUTHOR]

Aims: Antibody-labeled gold nanoparticles represent an attractive tool for cancer imaging and therapy. In this study, the anti-CD105 antibody was conjugated with gold nanoparticles (AuNPs) for the first time. The antibody biodistribution in mice before and after conjugation to AuNPs was studied, with a focus on tumor targeting. Materials & methods: Antibodies were radiolabeled with 89Zr before conjugation to AuNPs (5 nm). Immunonanoconjugates were characterized in vitro in terms of size, stability in plasma and binding to the target. Quantitative PET imaging and ICP-MS analysis assessed in vivo distribution and specific tumor targeting of tracers. Results: The tumor uptake of immunoconjugates was preserved up to 24 h after injection, with high tumor contrast and selective tumor targeting. No major tracer accumulation was observed over time in nonspecific organs. ICP-MS analysis confirmed the antibody specificity after nanoparticle conjugation. Conclusion: The anti-CD105 antibody conjugation to AuNPs did not greatly affect CD105-dependent tumor uptake and the efficacy of tumor targeting for cancer detection. Original submitted 29 April 2013; Revised submitted 20 September 2013 [ABSTRACT FROM AUTHOR]

Purpose: Hypoxia in head and neck squamous cell carcinoma (HNSCC) is associated with poor prognosis and outcome. F-Fluoroazomycin arabinoside (FAZA) is a positron emission tomography (PET) tracer developed to enable identification of hypoxic regions within tumor. The aim of this study was to evaluate the use of F-FAZA-PET for assessment of hypoxia before and during radiation therapy. Methods: Twelve patients with locally advanced HNSCC underwent F-FAZA-PET scans before and at fraction 7 and 17 of concomitant chemo-radiotherapy. A hypoxic voxel was defined as a voxel expressing a standardized uptake value (SUV) equal or above the SUV of the posterior contralateral neck muscles plus three standard deviations. The fractional hypoxic volume fraction (FHV) and the spatial move of hypoxic volumes during treatment were analyzed. Results: A hypoxic volume could be identified in ten patients before treatment. FAZA-PET FHV varied from 0 to 54.3 % and from 0 to 41.4 % in the primary tumor and in the involved node, respectively. Six out of these ten patients completed all the FAZA-PET-computed tomography (CT) during the radiotherapy. In all patients, FHV and SUV values decreased. All patient presented a spatial move of hypoxic volume, but only three patients had newborn hypoxic voxels after 17 fractions. Conclusion: This study indicated that F-FAZA-PET could be used to identify and quantify tumor hypoxia before and during concomitant radio-chemotherapy in patients with locally advanced HNSCC. In addition to the information on prognostic value, the use of F-FAZA-PET allowed the delineation of hypoxic volumes for dose escalation protocols. However, due to fluctuation of hypoxia during treatment, repeated scan will have to be performed (i.e. adaptive radiotherapy). [ABSTRACT FROM AUTHOR]