GRPr Antagonist 68Ga-SB3 PET/CT Imaging of Primary Prostate Cancer in Therapy-Naïve Patients.

The gastrin-releasing peptide receptor (GRPr) is overexpressed in prostate cancer (PCa) cells, making it an excellent tool for targeted imaging. The 68Ga-labeled GRPr antagonist SB3 has shown excellent results in preclinical and clinical studies and was selected for further clinical investigation. The aims of this phase I study were to investigate 68Ga-SB3 PET/CT imaging of primary PCa tumors and assess safety. More aims included an investigation of biodistribution and dosimetry and a comparison with pathology and GRPr expression. Methods: Ten therapy-naïve, biopsy-confirmed PCa patients planned for prostatectomy were included. A 3-h extensive PET/CT imaging protocol was performed within 2 wk before prostatectomy. Prostate tissue was evaluated for tumor localization and Gleason score, and in vitro autoradiography was performed to determine GRPr expression. Available MRI scans performed within 3 mo before the study were matched. For dosimetry, residence times were estimated and effective dose to the body as well as absorbed doses to organs were calculated using the IDAC dose model, version 2.1. Results: Administration of 68Ga-SB3 (187.4 ± 40.0 MBq, 40 ± 5 µg) was well tolerated; no significant changes in vital signs or laboratory results were observed. 68Ga-SB3 PET/CT showed lesions in 8 of 10 patients. Pathologic analysis revealed a total of 16 tumor lesions, of which PET/CT showed 14, resulting in a sensitivity of 88%. 68Ga-SB3 PET/CT imaging showed uptake in 2 large prostatic intraepithelial neoplasia foci, considered a precursor to PCa, resulting in an 88% specificity. Autoradiography of tumor lesions revealed heterogeneous GRPr expression and was negative in 4 patients. Both PET/CT-negative patients had a GRPr-negative tumor. In autoradiography-positive tumors, the level of GRPr expression showed a significant correlation to tracer uptake on PET/CT. Dosimetry calculations estimated the effective dose to be 0.0144 mSv/MBq, similar to other 68Ga-labeled radiopeptides. The highest absorbed dose was detected in the physiologic GRPr-expressing pancreas (0.198 mGy/MBq), followed by the bladder wall and kidneys. Conclusion:68Ga-SB3 PET/CT is a safe imaging method and a promising tool for early PCa imaging.

Isotopic Scintigraphy in Intrathecal Drug Delivery Failure: A Single-Institution Case Series.

BACKGROUND: The aim of this study was to assess the feasibility and diagnostic accuracy of an optimized 111 Indium-diethylenetriamine-penta-acetic-acid single-photon-emission computed tomography (CT) (111 In-DTPA SPECT-CT) examination in patients with suspected intrathecal drug delivery (ITDD) failure. MATERIALS AND METHODS: Retrospective analysis of routinely collected observational data from a case series of patients in the setting of the academic Center for Pain Medicine, Departments of Radiology and Nuclear Medicine and Neurosurgery. Twenty-seven patients participated between January 2014 and January 2019. Thirty-six optimized examinations including standardized pump flow rate with additional SPECT-CT imaging and a stepwise standardized analysis were performed. A 10 mL mixture of medication and 20 MBq 111In-DTPA was injected into the pump reservoir. Planar and SPECT-CT images were acquired at 24, 48, and 72 hours (h) after injection and at 96 hours and/or seven days, if needed. All images were reassessed by the first two authors using an optimized procedure. RESULTS AND CONCLUSIONS: Twenty-two abnormalities were identified in 21 examinations, with these abnormalities consisting of leakage (n = 7), spinal catheter obstruction (n = 7), and cerebrospinal fluid flow obstruction (n = 8). Interventions (n = 19) confirmed the cause of ITDD failure. A false-positive finding at follow-up (n = 1) and a false-negative finding (n = 1) were encountered. Sensitivity was 95% (20/21) and the specificity 93% (14/15). A significant difference (p < 0.001) was found between the accuracy of the conventical and the optimized analysis. The optimized 111 In-DTPA SPECT-CT examination is a powerful diagnostic tool for detecting the cause of ITDD failure.

18F-FDG PET/CT in the Diagnosis and Management of Continuous Flow Left Ventricular Assist Device Infections: A Case Series and Review of the Literature.

Implantable continuous flow left ventricular assist devices (LVADs) are increasingly used in end-stage heart failure treatment as a bridge-to-transplant and destination therapy (DT). However, LVADs still have major drawbacks, such as infections that can cause morbidity and mortality. Unfortunately, appropriate diagnosis of LVAD-related and LVAD-specific infections can be very cumbersome. The differentiation between deep and superficial infections is crucial in clinical decision-making. Despite a decade of experience in using fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) to diagnose various infections, its use in LVAD patients remains scarce. In this case series, we review the current evidence in literature and describe our single center experience using F-FDG PET/CT for the diagnosis and management of LVAD infections.

Comparison of three radiolabelled peptide analogues for CCK-2 receptor scintigraphy in medullary thyroid carcinoma.

PURPOSE: Cholecystokinin 2 (CCK-2) receptor overexpression has been demonstrated in a high percentage of medullary thyroid carcinomas (MTC). Analogous to somatostatin receptors, CCK-2 receptors might be viable targets for radionuclide scintigraphy and/or radionuclide therapy. Several CCK-2 receptor-binding radiopeptides have been developed, and some have been carried through into clinical studies. However, these studies are mostly limited and difficult to compare. The aim of this study was to evaluate the diagnostic and therapeutic potential of three promising CCK-2 receptor-binding radiopeptides in patients with MTC. METHODS: (111)In-DOTA-(D: )Asp-Tyr-Nle-Gly-Trp-Nle-Asp-Phe-NH(2) ((111)In-DOTA-CCK), a CCK analogue, and the gastrin-based ligands (99m)Tc-N(4)-Gly-(D: )Glu-(Glu)(5)-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH(2) ((99m)Tc-demogastrin 2) and (111)In-DOTA-(D: )Glu-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH(2) ((111)In-DOTA-MG11) were each administered to the same group of six patients. Planar images made at 3-5, 7 and 24 h p.i. were used for comparison of tumour visualisation and renal uptake. RESULTS: (99m)Tc-demogastrin 2 scintigraphy visualised all known lesions and new lesions in four of six patients. (111)In-DOTA-CCK and (111)In-DOTA-MG11 on the other hand missed several lesions; tumour uptake of these two radiopharmaceuticals was quite low. Comparison of retention of renal activity showed no major differences between the three radiopeptides. CONCLUSION: (99m)Tc-demogastrin 2 scintigraphy appeared most promising as a diagnostic tool in patients with MTC. Further studies are required to evaluate its value in patient management. Direct comparisons of the compounds studied strongly suggests that (111)In-DOTA-CCK and (111)In-DOTA-MG11 have less potential as imaging agents than (99m)Tc-demogastrin 2. These DOTA-linked compounds are considered unlikely to be useful for radionuclide therapy because of low tumour uptake.

99mTc-tetrofosmin or 99mTc-sestamibi for double-phase parathyroid scintigraphy?

Several years ago technetium-99m tetrofosmin was reported to localise parathyroid adenomas. The aim of this study was to compare the sensitivity of this radiopharmaceutical with that of (99m)Tc-sestamibi using a double-phase parathyroid scintigraphy protocol. Scans of 12 patients were evaluated visually and lesion to thyroid ratios were calculated. Nine of the patients were subsequently operated on; a total of eight parathyroid adenomas or hyperplastic glands were histologically confirmed in seven of the patients, while in one patient a parathyroid carcinoma was histologically proven. All of these patients had positive (99m)Tc-sestamibi scintigrams, whereas only two (99m)Tc-tetrofosmin scintigrams were positive. With (99m)Tc-sestamibi there was a significant increase in the lesion to thyroid ratio from 10 min to 90 min and 150 min p.i. which was not seen on scintigraphy with (99m)Tc-tetrofosmin. This makes (99m)Tc-tetrofosmin less suitable for double-phase parathyroid scintigraphy.