Phase II Trial Assessing the Repeatability and Tumor Uptake of [68Ga]Ga-HER2 Single-Domain Antibody PET/CT in Patients with Breast Carcinoma.

Human epidermal growth factor receptor 2 (HER2) status is used for decision-making in breast carcinoma treatment. The status is obtained through immunohistochemistry or in situ hybridization. These two methods have the disadvantage of necessitating tissue sampling, which is prone to error due to tumor heterogeneity or interobserver variability. Whole-body imaging might be a solution to map HER2 expression throughout the body. Methods: Twenty patients with locally advanced or metastatic breast carcinoma (5 HER2-positive and 15 HER2-negative patients) were included in this phase II trial to assess the repeatability of uptake quantification and the extended safety of the [68Ga]Ga-NOTA-anti-HER2 single-domain antibody (sdAb). The tracer was injected, followed by a PET/CT scan at 90 min. Within 8 d, the procedure was repeated. Blood samples were taken for antidrug antibody (ADA) assessment and liquid biopsies. On available tissues, immunohistochemistry, in situ hybridization, and mass spectrometry were performed to determine the correlation of HER2 status with uptake values measured on PET. If relevant preexisting [18F]FDG PET/CT images were available (performed as standard of care), a comparison was made. Results: With a repeatability coefficient of 21.8%, this imaging technique was repeatable. No clear correlation between PET/CT uptake values and pathology could be established, as even patients with low levels of HER2 expression showed moderate to high uptake. Comparison with [18F]FDG PET/CT in 16 patients demonstrated that in 7 patients, [68Ga]Ga-NOTA-anti-HER2 shows interlesional heterogeneity within the same patient, and [18F]FDG uptake did not show the same heterogeneous uptake in all patients. In some patients, the extent of disease was clearer with the [68Ga]Ga-NOTA-anti-HER2-sdAb. Sixteen adverse events were reported but all without a clear relationship to the tracer. Three patients with preexisting ADAs did not show adverse reactions. No new ADAs developed. Conclusion: [68Ga]Ga-NOTA-anti-HER2-sdAb PET/CT imaging shows similar repeatability to [18F]FDG. It is safe for clinical use. There is tracer uptake in cancer lesions, even in patients previously determined to be HER2-low or -negative. The tracer shows potential in the assessment of interlesional heterogeneity of HER2 expression. In a subset of patients, [68Ga]Ga-NOTA-anti-HER2-sdAb uptake was seen in lesions with no or low [18F]FDG uptake. These findings support further clinical development of [68Ga]Ga-NOTA-anti-HER2-sdAb as a PET/CT tracer in breast cancer patients.

18F-FDG PET/CT in Waldenström associated amyloidosis.

Amyloidoisis in patients with Waldenström macroglobulinemia (WM) mostly involves the heart, peripheral nerves and kidneys. Retroperitoneal amyloidosis is a rare finding. We describe a 62-year-old man with an incidental finding of a monoclonal gammopathy and elevated inflammatory parameters. Bilateral moderately active retroperitoneal infiltration with punctiform calcifications was found on fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) imaging. Taken together, these findings are suggestive of Waldenström associated amyloidosis. Computed tomography-guided retroperitoneal biopsy confirmed the diagnosis.

Fat misbehaving in the abdominal cavity: a pictorial essay.

Intra-abdominal fat is abundantly present in both the peritoneum and retroperitoneum. Fat necrosis or inflammation are common findings in abdominal imaging. The most common pathologies that we encounter are epiploic appendagitis, omental infarction, mesenteric panniculitis, and encapsulated fat necrosis. Less common entities that can occur are pancreatic saponification, heterotopic mesenteric ossification, and pseudolipoma of the capsule of Glisson. These entities can mimic more urgent pathologies such as appendicitis, diverticulitis, or malignancies.

Unilaterally Decreased Striatal Dopamine Transporter Caused by Venous Anomaly.

We describe a finding of unilaterally decreased binding of I-ioflupane in the basal ganglia in a 78-year-old woman that could be attributed to an underlying developmental venous anomaly.

PSMA Uptake in Mediastinal Sarcoidosis.

Prostate-specific membrane antigen (PSMA) is a cell surface glycoprotein which is frequently overexpressed on prostate cancer cells. Ga-PSMA PET/CT plays an increasing role in prostate cancer management. However, growing evidence suggests increased PSMA uptake in a variety of other malignant tumor entities and in some benign lesions. This report describes PSMA uptake in numerous thoracic lymph nodes in a patient with known mediastinal sarcoidosis. Knowledge and recognition of these possibilities are important to avoid scan misinterpretation.

Aspecific Uptake of 68GA-PSMA in Paget Disease of the Bone.

Ga-PSMA plays an increasing role in prostate cancer management, but several instances of false positivity have now been recognized. We present a patient with metastatic prostatic carcinoma who also showed overexpression of PSMA in Paget disease of the humerus on Ga-PSMA PET. This probably relates to bone remodeling and increased vascularity. It is important to be aware of this aspecific uptake because its recognition may avoid overstaging and may alter the therapeutic choice.

Healing Sacral Fracture Masquerading as Metastatic Bone Disease on a 68Ga-PSMA PET/CT.

Prostate-specific membrane antigen (PSMA) is a cell surface glycoprotein, which is frequently overexpressed on prostate cancer cells. A Ga-PSMA PET/CT can be used for early detection of lymph node or bone metastases after radical prostatectomy when there is biochemical recurrence. This report describes PSMA uptake in a healing fracture masquerading as metastatic bone disease in a patient with a history of prostate adenocarcinoma. Clinicians reporting Ga-PSMA PET/CT should be aware of this potential important pitfall.

Intratumoral Delivery of TriMix mRNA Results in T-cell Activation by Cross-Presenting Dendritic Cells.

Modulating the activity of tumor-infiltrating dendritic cells (TiDC) provides opportunities for novel cancer interventions. In this article, we report on our study of the uptake of mRNA by CD8α(+) cross-presenting TiDCs upon its intratumoral (i.t.) delivery. We exploited this property to deliver mRNA encoding the costimulatory molecule CD70, the activation stimuli CD40 ligand, and constitutively active Toll-like receptor 4, referred to as TriMix mRNA. We show that TiDCs are reprogrammed to mature antigen-presenting cells that migrate to tumor-draining lymph nodes (TDLN). TriMix stimulated antitumor T-cell responses to spontaneously engulfed cancer antigens, including a neoepitope. We show in various mouse cancer models that i.t. delivery of TriMix mRNA results in systemic therapeutic antitumor immunity. Finally, we show that the induction of antitumor responses critically depends on TiDCs, whereas it only partially depends on TDLNs. As such, we provide a platform and a mechanistic rationale for the clinical testing of i.t. administration of TriMix mRNA.

Correlative bone imaging in a case of Schnitzler's syndrome and brief review of the literature.

UNLABELLED: Schnitzler's syndrome is a rare disease characterized by a monoclonal IgM (or IgG) paraprotein, a nonpruritic urticarial skin rash, and 2 (or 3) of the following: recurrent fever, objective signs of abnormal bone remodeling, elevated CRP level or leukocytosis, and a neutrophilic infiltrate on skin biopsy. It responds well to treatment with the interleukine-1-inhibitor anakinra. We report the bone scintigraphy and MRI findings in a 45 years old man with this syndrome and compare them with data from the literature. CONCLUSION: None of the imaging findings are specific, but they lead to a differential diagnosis including infiltrative diseases (e.g. systemic mastocytosis or Erdheim-Chester disease) and dysplastic diseases (e.g. melorheostosis, Camurati-Engelmann disease or van Buchem disease). The bone scintigraphy pattern may be very suggestive of the correct diagnosis and of bone involvement in this syndrome.

Camelid reporter gene imaging: a generic method for in vivo cell tracking.

BACKGROUND: To combine the sensitivity of bioluminescent imaging (BLI) with the 3D and quantitative properties of pinhole single-photon emission computed tomography (SPECT)/micro-computed tomography (CT) (phSPECT/micro-CT), we generated stable cell lines that express a yellow-fluorescent protein (YFP) and Gaussia luciferase (GLuc) fusion protein (YFP/GLuc). For in vivo phSPECT detection of this YFP/GLuc protein, a nanobody, targeted against yellow and green fluorescent proteins (anti-YFP-Nb), was site specifically labelled with (99m)Tc. METHODS: Human embryonic kidney cells (HEK293T) were cultured and passaged every 3 days. 10E5 cells were transduced with YFP/GLuc-containing vector: both membrane-targeted (MT-YFP/GLuc) and non-targeted (YFP/GLuc) fusion proteins were developed. These vectors were compared against a SKOV-3 cell line stably expressing green fluorescent-firefly luciferase (GFP/Fluc) and HEK293T cells expressing red fluorescent protein in combination with a Gaussia luciferase (Red/GLuc). Transduction efficiencies were scored by fluorescence microscopy, and transduced cells were enriched by fluorescence-activated cell sorting (FACS). GLuc and FLuc functionality was tested in vitro by list-mode BLI. Subsequently, cells were transplanted subcutaneously in athymic (nu/nu) mice (MT-YFP/GLuc: n = 4, YFP/GLuc: n = 6, GFP/FLuc: n = 6, Red/GLuc: n = 4). Labelling efficiency of anti-YFP-Nb was measured using instant thin layer chromatography. One week after transplantation, (99m)Tc-labelled anti-YFP-Nb was injected intravenously and pinhole (ph) SPECT/micro-CT was performed, followed by in vivo BLI. RESULTS: Cells showed high levels of fluorescence after transduction. The cells containing the MT-YFP/GLuc were positive on fluorescence microscopy, with the fluorescent signal confined to the cell membrane. After cell sorting, transduced cells were assayed by BLI and showed a significantly higher light output both in vitro and in vivo compared with non-transduced HEK293T cells. The anti-YFP-Nb labelling efficiency was 98%, and subsequent phSPECT/micro-CT demonstrated visible cell binding and significantly higher transplant-to-muscle ratio for both the MT-YFP/GLuc and YFP/GLuc transplanted cells, compared with the GFP/FLuc and Red/GLuc group. CONCLUSION: This study provides a proof of principle for a nanobody-based cell tracking method, using a YFP/GLuc fusion protein and anti-YFP-Nb in a model of subcutaneously transplanted transduced HEK293T cells.

Testicular cell transplantation into the human testes.

OBJECTIVE: To translate spermatogonial stem cell (SSC) transplantation towards a clinical application. DESIGN: Mouse green fluorescent protein (GFP)-positive testicular cells were labeled with (99m)technetium and microbubbles. These labeled cells were injected into the rete testis of isolated human testes under ultrasound guidance. Three different conditions were tested: 1) 800 µL of a 20 million cells/mL suspension; 2) 800 µL of a 10 million cells/mL suspension; and 3) 1,400 µL of a 10 million cells/mL suspension. After injection, the human cadaver testes were analyzed with the use of single-photon-emission computerized tomography (SPECT) imaging and histology. SETTING: Laboratory research environment. PATIENT(S): Cadaver testes, obtained from autopsies at the pathology department. INTERVENTION(S): Ultrasound-guided injection of mouse GFP-positive testicular cells. MAIN OUTCOME MEASURE(S): Presence of radioactive-labeled cells in the human cadaver testes and GFP-positive cells in the seminiferous tubules. RESULT(S): In all of the experimental groups, GFP-positive cells were observed in the seminiferous tubules, near and far from the rete testis, but also in the interstitium. On SPECT, significant difference was seen between the group injected with 800 µL of a 20 million cells/mL suspension (1,654.6 ± 907.6 mm³) and the group injected with 1,400 µL of a 10 million cells/mL suspension (3,614.9 ± 723.1 mm³). No significant difference was reached in the group injected with 800 µL of a 10 million cells/mL suspension. CONCLUSION(S): Injecting cells in the human cadaver testis is feasible, but further optimization is required.

Improved quantification in pinhole gated myocardial perfusion SPECT using micro-CT and ultrasound information.

Absolute quantification using single photon emission computed tomography (SPECT) was demonstrated in vitro and in large immobile organs in vivo. To determine the feasibility of in vivo quantification of myocardial perfusion in pinhole gated SPECT, we added an ultrasound derived partial volume correction factor to attenuation and scatter corrections, in combination with gated acquisitions. In nine male Wistar rats, cardiac ultrasound was performed prior to SPECT/CT scans to determine the myocardial wall thickness. SPECT/CT scans were then performed 30 min after injection of (99m) Tc Tetrofosmin. Animals were killed and six midventricular segments of the left ventricle were excised and counted in a γ-well counter. Using AMIDE, regional myocardial activity was measured after combined scatter correction (SC) and attenuation correction (AC). These image derived activities were compared with the ex vivo counted activity. To correct for the partial volume effect, a recovery coefficient was determined from a phantom study, to determine the thickness specific partial volume effect. Combined AC and SC led to a significant underestimation of activity compared with ex vivo data (root mean squared error = 0.145 mCi g(-1)). The recovery coefficient calculated from the phantom study showed a linear relationship with object size from 1 to 6 mm, positioned in the vicinity of the center of the field of view (R(2) = 0.98). Correction of nongated SPECT images with a recovery coefficient derived from the diastolic phase results in a global overestimation with root mean squared error = 0.04 mCi g(-1). Nongated SPECT images corrected with a recovery coefficient with a weighted average ratio diastolic and systolic phase led to an improved root mean squared error of 0.03 mCi g(-1). Combining attenuation correction with scatter correction and a gated partial volume correction yields the best correlation with ex vivo counting (root mean squared error = 0.021 mCi g(-1) (systolic) and 0.025 mCi g(-1) (diastolic). This study demonstrates a method for improved segmental myocardial perfusion quantification in pinhole gated SPECT, using combined attenuation-, scatter- and ultrasound-derived partial volume effect corrections.

Preclinical evaluation of TriMix and antigen mRNA-based antitumor therapy.

The use of tumor-associated antigen (TAA) mRNA for therapeutic purposes is under active investigation. To be effective, mRNA vaccines need to deliver activation stimuli in addition to TAAs to dendritic cells (DC). In this study, we evaluated whether intranodal delivery of TAA mRNA together with TriMix, a mix of mRNA encoding CD40 ligand, constitutive active Toll-like receptor 4 and CD70, results in the in situ modification and maturation of DCs, hence, priming of TAA-specific T cells. We showed selective uptake and translation of mRNA in vivo by lymph node resident CD11c(+) cells. This process was hampered by codelivery of classical maturation stimuli but not by TriMix mRNA. Importantly, TriMix mRNA induced a T-cell-attracting and stimulatory environment, including recruitment of antigen-specific CD4(+) and CD8(+) T cells and CTLs against various TAAs. In several mouse tumor models, mRNA vaccination was as efficient in CTL induction and therapy response as vaccination with mRNA-electroporated DCs. Together, our findings suggest that intranodal administration of TAA mRNA together with mRNA encoding immunomodulating molecules is a promising vaccination strategy.

Rapid hepatic clearance of 99mTc-TMEOP: a new candidate for myocardial perfusion imaging.

BACKGROUND: (99m)Tc labeled radiotracers used in clinical practice lack the perfect characteristics for myocardial perfusion imaging. In particular, the high liver uptake can interfere in the interpretation of the inferior myocardial wall. Within the tricarbonyl approach, we used tris(pyrazolyl)methane (99m)Tc organometallic complexes as a lead structure. Herein we present the production, in vivo and in vitro metabolic studies in rats and the first in vivo biodistribution in rats for tri-methoxy-tris-pyrazolyl-(99m)Tc-(CO)(3) ((99m)Tc-TMEOP), compared with (99m)Tc-sestamibi and (99m)Tc-tetrofosmin. METHODS: The chemical identity of (99m)Tc-TMEOP was characterized by RP-HPLC. The octanol-water partition coefficient was determined under physiological conditions. In vitro stability and protein binding were determined using RP-HPLC. In vivo stability was determined in blood, heart, liver and kidney homogenates, intestine and urine using RP-HPLC. In vivo biodistribution was determined using dynamic planar acquisitions. Pinhole gated SPECT images were performed in other animals. Cardiac, liver and lung uptake were expressed as differential uptake ratios by drawing regions of interest in the organs of interest and around the total body. Heart-liver and heart-lung ratios were derived. Cardiac uptake was also expressed as percentage of injected activity. SPECT images were processed to determine the heart-liver ratio on SPECT images, to compare functional parameters between different tracers and to visualize homogeneous intracardiac tracer distribution. RESULTS: (99m)Tc-TMEOP is a moderately lipophilic cation, is stable and does not undergo any transformation in vitro. (99m)Tc-TMEOP also shows a high in vivo stability. In vivo imaging shows liver kinetics faster than those of (99m)Tc-sestamibi and (99m)Tc-tetrofosmin. Cardiac uptake and functional analysis of pinhole gated SPECT data are comparable to those of (99m)Tc-sestamibi and (99m)Tc-tetrofosmin. CONCLUSION: Although (99m)Tc-TMEOP shows a cardiac uptake between those of (99m)Tc-sestamibi and (99m)Tc-tetrofosmin, a better heart-liver ratio is obtained due to the faster liver washout. These results suggest possible faster cardiac perfusion imaging using (99m)Tc-TMEOP without liver activity interference.

Utility of pelvic bone SPET in imaging urinary bladder filling defects in urinary bladder carcinoma.

Urinary bladder carcinoma sometimes can be recognized on bone scans as a filling defect in the bladder. This paper illustrates in three patients that the filling defects of urinary bladder on pelvic bone single photon emission tomography (SPET) scans in cases of bladder carcinoma correspond to those on computerized tomography (CT). In one patient, the void sign could only be discerned on the SPET images, but not on the planar images. In the same patient, the filling defect was almost entirely surrounded by urinary activity, suggesting an intrinsic bladder lesion. The differential diagnosis of filling defects is presented. The above findings are compared to other related studies, although we have found no similar cases in the literature. When compared with CT, pelvic SPET is more sensitive than planar imaging in recognizing bladder filling defects on bone scans and may allow distinguish between intrinsic and extrinsic bladder lesions.

Regional quantitative analysis of small animal myocardial sympathetic innervation and initial application in streptozotocin induced diabetes.

BACKGROUND: In several disease models it is known that heterogeneous dysinnervation occurs in the sympathetic nervous system. We therefore adapted the (123)I-MIBG imaging procedure in small animals to allow quantification of both global and regional uptake and wash-out rate using high specific activity (123)I-MIBG in the myocardium of rats. After evaluation of the image procedure in normal animals, we then applied our imaging protocol to visualize the regional dysinnervation in cardiac autonomic neuropathy occurring in streptozotocin-induced diabetes. METHODS: Seven normal Lewis rats underwent (123)I-MIBG pinhole SPECT with low specific activity (123)I-MIBG (lsa MIBG) and high specific activity (123)I-MIBG (hsa MIBG) with a 2 week interval. Twelve normal rats and 12 rats 8 weeks after streptozotocin injection underwent the same hsa MIBG imaging protocol. The imaging protocol consisted of two SPECT acquisitions for every animal. The imaging sequence started at 20 min after tracer injection. The percentage of injected activity (%IA) and the wash-out rate in the global myocardium were measured. Left ventricular regional MIBG kinetics were analyzed in the six midventricular segments of the 17 segment model. RESULTS: Compared with lsa MIBG, the wash-out rate of hsa MIBG was significantly slower, in association with a higher cardiac uptake. Regional analysis showed a maximal uptake in the anterolateral segment, without significant differences between segments. We noted a significantly higher global wash-out rate in the streptozotocin group compared to controls (p < 0.05). Regional analysis confirmed the increased wash-out rate, reaching statistical significance in the inferior and the inferoseptal walls. CONCLUSION: High-quality (123)I-MIBG images and accurate measurements can be obtained using hsa (123)I-MIBG with image acquisitions performed at relatively early time points. Small animal MIBG SPECT imaging allows for regional analysis of the myocardium. In the streptozotocin group, wash-out of MIBG is globally increased, compatible with a higher sympathetic tonus or decreased reuptake of MIBG. The highest increase is located in the inferior, inferoseptal and anteroseptal walls. These findings further suggest the occurrence of diabetic cardiomyopthy after streptozotocin injection.