Pierre-Olivier Kotzki

Cell membrane is a more sensitive target than cytoplasm to dense ionization produced by auger electrons.

Abstract Pouget, J-P., Santoro, L., Raymond, L., Chouin, N., Bardiès, M., Bascoul-Mollevi, C., Huguet, H., Azria, D., Kotzki, P-O., Pè legrin, M., Vivès, E. and Pèlegrin, A. Cell Membrane is a More Sensitive Target than Cytoplasm to Dense Ionization Produced by Auger Electrons. Radiat. Res. 170, 192–200 (2008). To improve radioimmunotherapy with Auger electron emitters, we assessed whether the biological efficiency of 125I varied according to its localization. A-431 and SK-OV-3 carcinoma cells were incubated with increasing activities (0–4 MBq/ml) of 125I-labeled vectors targeting the cell membrane, the cytoplasm or the nucleus. We then measured cell survival by clonogenic assay and the mean radiation dose to the nucleus by assessing the cellular medical internal radiation dose (MIRD). The relationship between survival and the radiation dose delivered was investigated with a linear mixed regression model. For each cell line, we obtained dose–response curves for the three targets and the reference values (i.e., the dose leading to 75, 50 or 37% survival). When cell survival was expressed as a function of the total cumulative decays, nuclear 125I disintegrations were more harmful than disintegrations in the cytoplasm or at the cell membrane. However, when survival was expressed as a function of the mean radiation dose to the nucleus, toxicity was significantly higher when 125I was targeted to the cell membrane than to the cytoplasm. These findings indicate that the membrane is a more sensitive target than the cytoplasm for the dense ionization produced by Auger electrons. Moreover, cell membrane targeting is as cytotoxic as nuclear targeting in SK-OV-3 cells. We suggest that targeting the membrane rather than the cytoplasm may contribute to the development of more efficient radioimmunotherapies based on Auger electron radiation, also because most of the available vectors are directed against cell surface antigens.

Major increase in brain natriuretic peptide indicates right ventricular systolic dysfunction in patients with heart failure.

This study sought to investigate whether the presence of right ventricular systolic dysfunction with pre‐existing left ventricular systolic dysfunction is associated with higher plasma brain natriuretic peptide (BNP) levels, compared with patients with isolated left ventricular dysfunction. Eighty‐five patients referred for evaluation of isotopic ventricular function were prospectively included in the study. Left (LVEF) and right (RVEF) ventricular ejection fractions were evaluated by gated blood pool scintigraphy and compared with plasma BNP levels. BNP correlated negatively with LVEF, except in patients with ischaemic heart disease (P=0.09) and in patients with LVEF<40% (P=0.11). In contrast, BNP levels correlated negatively with RVEF for all subgroups. Among patients with RVEF<40%, no significant BNP difference was found between patients with or without additional left ventricular systolic dysfunction (P=0.51). Among patients with LVEF<40%, plasma BNP levels were significantly higher in patients with RVEF<40% than in patients with RVEF≥40% (P=0.004) whereas age, renal function, clinical findings, ventricular volumes, LVEF or medication were not significantly different. In conclusion, an important increase in BNP levels in patients with left ventricular systolic dysfunction should be considered by cardiologists as an indication of high risk of right ventricular dysfunction and should justify further investigation.

Relevance of 2D radiographic texture analysis for the assessment of 3D bone micro-architecture.

Although the diagnosis of osteoporosis is mainly based on dual x-ray absorptiometry, it has been shown that trabecular bone micro-architecture is also an important factor in regard to fracture risk. In vivo, techniques based on high-resolution x-ray radiography associated to texture analysis have been proposed to investigate bone micro-architecture, but their relevance for giving pertinent 3D information is unclear. Thirty-three calcaneus and femoral neck bone samples including the cortical shells (diameter: 14mm, height: 30-40mm) were imaged using 3D-synchrotron x-ray micro-CT at the ESRF. The 3D reconstructed images with a cubic voxel size of 15μm were further used for two purposes: (1) quantification of three-dimensional trabecular bone micro-architecture, (2) simulation of realistic x-ray radiographs under different acquisition conditions. The simulated x-ray radiographs were then analyzed using a large variety of texture analysis methods (co-occurrence, spectral density, fractal, morphology, etc.). The range of micro-architecture parameters was in agreement with previous studies and rather large, suggesting that the population was representative. More than 350 texture parameters were tested. A small number of them were selected based on their correlation to micro-architectural morphometric parameters. Using this subset of texture parameters, multiple regression allowed one to predict up to 93% of the variance of micro-architecture parameters using three texture features. 2D texture features predicting 3D micro-architecture parameters other than BV/TV were identified. The methodology proposed for evaluating the relationships between 3D micro-architecture and 2D texture parameters may also be used for optimizing the conditions for radiographic imaging. Further work will include the application of the method to physical radiographs. In the future, this approach could be used in combination with DXA to refine osteoporosis diagnosis.

Noninternalizing Monoclonal Antibodies Are Suitable Candidates for 125I Radioimmunotherapy of Small-Volume Peritoneal Carcinomatosis

We have previously shown that, in vitro, monoclonal antibodies (mAbs) labeled with the Auger electron emitter 125I are more cytotoxic if they remain at the cell surface and do not internalize in the cytoplasm. Here, we assessed the in vivo biologic efficiency of internalizing and noninternalizing 125I-labeled mAbs for the treatment of small solid tumors. Methods: Swiss nude mice bearing intraperitoneal tumor cell xenografts were injected with 37 MBq (370 MBq/mg) of internalizing (anti-HER1) 125I-m225 or noninternalizing (anti-CEA) 125I-35A7 mAbs at days 4 and 7 after tumor cell grafting. Nonspecific toxicity was assessed using the irrelevant 125I-PX mAb, and untreated controls were injected with NaCl. Tumor growth was followed by bioluminescence imaging. Mice were sacrificed when the bioluminescence signal reached 4.5 × 107 photons/s. Biodistribution analysis was performed to determine the activity contained in healthy organs and tumor nodules, and total cumulative decays were calculated. These values were used to calculate the irradiation dose by the MIRD formalism. Results: Median survival (MS) was 19 d in the NaCl-treated group. Similar values were obtained in mice treated with unlabeled PX (MS, 24 d) and 35A7 (MS, 24 d) or with 125I-PX mAbs (MS, 17 d). Conversely, mice treated with unlabeled or labeled internalizing m225 mAb (MS, 76 and 77 d, respectively) and mice injected with 125I-35A7 mAb (MS, 59 d) showed a significant increase in survival. Irradiation doses were comparable in all healthy organs, independently from the mAb used, whereas in tumors the irradiation dose was 7.4-fold higher with 125I-labeled noninternalizing than with internalizing mAbs. This discrepancy might be due to iodotyrosine moiety release occurring during the catabolism of internalizing mAbs associated with high turnover rate. Conclusion: This study indicates that 125I-labeled noninternalizing mAbs could be suitable for radioimmunotherapy of small solid tumors and that the use of internalizing mAbs should not be considered as a requirement for the success of treatments with 125I Auger electrons.

Brief Intraperitoneal Radioimmunotherapy of Small Peritoneal Carcinomatosis Using High Activities of Noninternalizing 125I-Labeled Monoclonal Antibodies

We assessed the efficiency and toxicity of brief intraperitoneal radioimmunotherapy using high activities of 125I-labeled monoclonal antibody (mAb) in the treatment of small-volume peritoneal carcinomatosis. Methods: Brief intraperitoneal radioimmunotherapy consisted of a 185-MBq (740 MBq/mg) intraperitoneal injection of 125I-35A7 (an anti–carcinoembryonic antigen mAb) into athymic nude mice 4 d after peritoneal tumor xenografting and, after 1 h, abundant washing of the peritoneal cavity with saline solution to remove unbound radioactivity. Another group of mice received this treatment plus a 37-MBq intravenous injection of 125I-35A7 on day 7 or 11 after grafting. Control groups received a brief treatment followed by an additional intravenous injection on day 7 of either saline solution or irrelevant 125I-PX. Tumor growth was monitored by bioluminescence imaging and SPECT/CT, and hematologic toxicity was evaluated by complete blood counts. Survival time was reported, and the mice were sacrificed when the bioluminescence signal reached 4.5 × 107 photons/s. The biodistribution of 125I-35A7 mAb after intravenous or brief treatment was assessed, and the mean absorbed irradiation dose by organs and tumors was calculated using the MIRD formalism. Results: Mild, transient hematologic toxicity was observed after the brief treatment plus intravenous 125I-mAb, with no weight loss. Median survival increased from 32 d in the control groups, to 46 d in the brief treatment group, to 66 d in the group additionally receiving intravenous treatment on day 11, to 73 d in the group additionally receiving intravenous treatment on day 7. The brief treatment alone resulted in a 3-fold higher tumor-to-blood uptake ratio than did the standard intravenous treatment, and the mean absorbed irradiation doses by tumors were 11.6 Gy for the brief treatment and 16.7 Gy for the additional intravenous treatment. For healthy tissues other than blood, the mean absorbed irradiation dose did not exceed 1 Gy after brief treatment and 4.2 Gy after intravenous treatment. Conclusion: The efficiency, low toxicity, and high tumor–to–healthy tissue uptake ratio associated with brief intraperitoneal 125I-35A7 radioimmunotherapy suggest that this method can be used in combination with radiation-synergistic drugs in the therapy of small-volume peritoneal carcinomatosis after cytoreductive surgery.

Theoretical and experimental limits of triple photon energy absorptiometry in the measurement of bone mineral

Theoretical and experimental studies have been conducted to explore the possibilities of triple photon energy absorptiometry in the measurement of bone mineral content. The purpose of this technique is to correct the measured bone mineral density for fat and soft tissues. However, theoretical considerations lead us to doubt the precision and accuracy of such measurements. In a first approximation the absorption coefficient can be split into Compton and photoelectric energy-independent factors. A consequence of such a model is the impossibility of finding more than two independent mass attenuation coefficients for different energies. The existence of an energy-dependent third factor may justify the use of triple photon energy absorptiometry but experimental tests and numerical simulations have shown that its value is too low for triple photon energy absorptiometry to be considered as an adequate method for the measurement of bone mineral content.

Phase II Study of a Radiotherapy Total Dose Increase in Hypoxic Lesions Identified by 18 F-Misonidazole PET/CT in Patients with Non–Small Cell Lung Carcinoma (RTEP5 Study)

See an invited perspective on this article on page 1043. This multicenter phase II study investigated a selective radiotherapy dose increase to tumor areas with significant 18F-misonidazole (18F-FMISO) uptake in patients with non–small cell lung carcinoma (NSCLC). Methods: Eligible patients had locally advanced NSCLC and no contraindication to concomitant chemoradiotherapy. The 18F-FMISO uptake on PET/CT was assessed by trained experts. If there was no uptake, 66 Gy were delivered. In 18F-FMISO–positive patients, the contours of the hypoxic area were transferred to the radiation oncologist. It was necessary for the radiotherapy dose to be as high as possible while fulfilling dose-limiting constraints for the spinal cord and lungs. The primary endpoint was tumor response (complete response plus partial response) at 3 mo. The secondary endpoints were toxicity, disease-free survival (DFS), and overall survival at 1 y. The target sample size was set to demonstrate a response rate of 40% or more (bilateral α = 0.05, power 1-β = 0.95). Results: Seventy-nine patients were preincluded, 54 were included, and 34 were 18F-FMISO–positive, 24 of whom received escalated doses of up to 86 Gy. The response rate at 3 mo was 31 of 54 (57%; 95% confidence interval [CI], 43%–71%) using RECIST 1.1 (17/34 responders in the 18F-FMISO–positive group). DFS and overall survival at 1 y were 0.86 (95% CI, 0.77–0.96) and 0.63 (95% CI, 0.49–0.74), respectively. DFS was longer in the 18F-FMISO–negative patients (P = 0.004). The radiotherapy dose was not associated with DFS when adjusting for the 18F-FMISO status. One toxic death (66 Gy) and 1 case of grade 4 pneumonitis (>66 Gy) were reported. Conclusion: Our approach results in a response rate of 40% or more, with acceptable toxicity. 18F-FMISO uptake in NSCLC patients is strongly associated with poor prognosis features that could not be reversed by radiotherapy doses up to 86 Gy.

Glucose metabolism in nine patients with probable sporadic Creutzfeldt–Jakob disease: FDG-PET study using SPM and individual patient analysis

Only one large series using statistical parametric mapping (SPM) reports on FDG-PET in sporadic (Heidenhain and non-Heidenhain variant) Creutzfeldt–Jakob disease (sCJD), describing hypometabolism in bilateral parietal, frontal, and occipital cortices. Our aim was to study FDG-PET in non-Heidenhain probable sCJD patients in order to assess the most pertinent FDG-PET pattern, and to compare FDG-PET and MRI data. We used both SPM and NeuroGam® software analysis, compared with healthy controls, to describe the FDG-PET abnormalities. Individual FDG-PET and MRI–DWI data were compared. SPM group analysis showed lateralized hypometabolism in the medial parietal cortex, the lateral and medial frontal (sparing Brodmann’s area 4 and 6 and the anterior cingulate cortex), and lateral parietal cortex, in the absence of basal ganglia or cerebellar hypometabolism. The most severe hypometabolism was seen in Brodmann’s area 31, and to a lesser degree area 23 (both areas correspond to the posterior cingulate cortex) and the precuneus. On individual analysis using NeuroGam® software, additional variable temporal cortex and frequent basal ganglia (with caudate nucleus as the most frequently involved structure) hypometabolism was seen, in the absence of cerebellar hypometabolism. The cerebral lobe cortex was more frequently and more severely hypometabolic than basal ganglia structures. Concordance between FDG-PET and MRI abnormalities was most often present for both the cerebral lobe cortex and the basal ganglia. In the case of discordance, FDG-PET was more sensitive than MRI for the cortex, whereas MRI was more sensitive than FDG-PET for the basal ganglia. When pathological, both cortical lobe cortex and basal ganglia involvement were slightly more often lateralized on FDG-PET than on MRI. Despite the presence of overlapping features with other diseases presenting with rapidly progressive dementia, the FDG-PET pattern we found in our non-Heidenhain sCJD patients may help in the differential diagnosis of rapidly progressive dementia.

Hemiballism due to an ipsilateral subthalamic nucleus lesion

An 87-year-old right-handed man with untreated hypertension and hypercholesterolaemia presented with acute flinging and throwing movements of the left upper and lower limb. Clinical examination confirmed involuntary, irregular, wide amplitude movements of the left limbs consistent with left hemiballism in the absence of other neurological deficit. Blood count, CRP, glucose level, calcium, renal and liver function tests, ANF, lupus anticoagulant, anticardiolipin antibodies, thyroid function, serology of HIV, and arterial blood gas analysis were all normal. Brain MRI showed an acute infarction in the left (i.e. ipsilateral to the hemiballistic movements) subthalamic nucleus (STN) zone (Fig. 1), together with signs of chronic ischaemic microangiopathy in the brainstem and the periventricular areas (Fig. 2). [F] FDG PET performed 1 week after symptom onset revealed hypometabolism in the left hemispheric cortex (preserving only the anteromedial part of the frontal lobe) and the left caudate nucleus and the putamen (Fig. 1), probably due to deafferentation via connections between the STN and the ipsilateral basal ganglia system and the cortex, respectively. Carotid duplex sonography showed bilateral nonstenotic carotid atheroma. Electrocardiography and transthoracic echocardiography were normal. Recent infarction was probably due to occlusion of a small artery related to untreated cardiovascular risk factors. Secondary prevention treatment for ischaemic stroke was started. Neuropsychological testing 1 week after symptom onset showed a mild to moderate amnestic syndrome with preserved executive functions. Hemiballism disappeared progressively over the following months. [F] FDG PET 5 months after hemiballism onset showed near complete recovery of hypometabolism (Fig. 1), and neuropsychological testing normalized. Historically, acute hemiballism was thought to be related almost exclusively to contralateral (ischaemic or haemorrhagic) STN lesions. However, recently the era of modern neuroimaging has allowed identification of lesions often outside the STN (e.g. thalamus, globus pallidum, putamen, caudate nucleus, white matter, and cortex) [1]. The vast majority of lesions are contralateral to the hemiballism. Only a few cases with ipsilateral STN lesions have been described [2, 3]. The pathophysiology of ipsilateral hemiballism is poorly understood. The possibility that the STN exerts a bilateral control of motor function may explain this. This is supported by the observation that unilateral stereotaxic neurosurgery in Parkinson’s disease frequently results in bilateral improvement of abnormal movements. Anatomic pathways related to this bilateral control are unknown. [F] FDG PET in our patient nicely showed the connections between the STN and the other ipsilateral brain structures. DimitriRenard (&) A. Le Floch G. Castelnovo P. Labauge Department of Neurology, CHU Nimes, Hopital Caremeau, Place du Pr Debre, 30029 Nimes Cedex 4, France e-mail: dimitrirenard@hotmail.com

Assessment of the Stratos, a New Pencil-Beam Bone Densitometer: Dosimetry, Precision, and Cross Calibration

The goal of this study was to assess a new pencil-beam densitometer, the Stratos (Diagnostic Medical Systems, Pérols, France). Evaluation of the dosimetry and precision were done together with an in vivo cross-calibration study performed with the fan beam densitometer Discovery A (Hologic, Bedford, MA). The results indicated that the Stratos performed bone mineral density (BMD) measurements with a good precision, low radiation dose, and good agreement with the Discovery A. The air dose, measured by an ionization chamber, was 40 μGy. The effective dose was assessed using an anthropomorphic phantom and thermoluminescent detectors resulting in 1.96 and 0.31 μSv for a lumbar spine and proximal femur scan, respectively. The average scattered dose rate at a distance of 1m from the device was 1.06 and 1.21 μSv.h(-1) in the lumbar spine and left proximal femur scan mode, respectively. For the precision evaluation, 30 patients underwent 2 lumbar spine and 2 proximal femur scans with repositioning after each scan. The percentage root-mean-square coefficient of variation was 1.22%, 1.38%, 2.11%, and 0.86% for the lumbar spine (L1-L4), lumbar spine (L2-L4), femoral neck, and total hip, respectively. The cross-calibration studies were done on 57 patients (60 ± 9 yr). Lumbar spine, left neck, and left total hip mean BMD were 3.10% lower and 11.94% and 8.83% higher, respectively, with the Stratos compared with the Discovery A. Cross-calibration equations were calculated with a correlation coefficient of 98% (p<0.01) for the lumbar spine (L2-L4), 94% (p<0.01) for the left neck, and 92% (p<0.01) for the left total hip. After standardizing the Stratos measures using the cross-calibration equations, LINs concordance correlation coefficient was 0.98, 0.93, and 0.92 for the lumbar spine (L2-L4), left neck, and total hip, respectively.