The Performance of FDA-Approved PET Imaging Agents in the Detection of Prostate Cancer

Preliminary evaluation of a novel PSMA-targeting radiopharmaceutical [68Ga]Ga/[177Lu]Lu-NYM032 for theranostic use in prostate cancer

PURPOSE

A novel theranostic radiopharmaceutical targeting prostate-specific membrane antigen (PSMA), [68Ga]Ga/[177Lu]Lu-NYM032, was developed and its diagnostic and therapeutic potential in the treatment of prostate cancer (PCa) was preliminarily evaluated.

METHODS

The diagnostic efficacy of the PET tracer [68Ga]Ga-NYM032 was first evaluated in PSMA-positive xenograft-bearing models (LNCaP models), followed by evaluation in 10 PCa patients using [68Ga]Ga-PSMA617 a comparator. Finally, the therapeutic potential of [177Lu]Lu-NYM032 was evaluated in LNCaP models.

RESULTS

[68Ga]Ga/[177Lu]Lu-NYM032 was well-tolerated, and no adverse events were observed in the preclinical and clinical studies. [68Ga]Ga-NYM032 demonstrated PSMA specificity and high radioactive uptake in LNCaP tumors. [68Ga]Ga-NYM032 uptake (SUVmax) did not differ from [68Ga]Ga-PSMA617 uptake in the same in situ lesions at the same p.i. time point (median 9.40 vs. 6.85, P = 0.123, n = 8). Compared with [68Ga]Ga-PSMA617 uptake, [68Ga]Ga-NYM032 uptake was significantly higher in osseous metastases (median 5.10 vs. 3.88, P < 0.001, n = 48), and higher in lymph node metastases (median 7.81 vs. 5.46, n = 2). [177Lu]Lu-NYM032 showed high aggregation in the lesions of LNCaP models and long retention times. [177Lu]Lu-NYM032 could inhibit tumor progression in LNCaP models, and its therapeutic efficiency strengthened with increasing radio-dosage (18.5-74 MBq/mouse). The tumor volume in the high radio-dosage treatment group (74 MBq/mouse) was significantly smaller than that in the blank control group at 21 days p.i. (107.14 ± 13.68 mm3 vs. 1351.86 ± 249.98 mm3, P < 0.001, n = 7).

CONCLUSION

[68Ga]Ga/[177Lu]Lu-NYM032 has considerable potential as a novel and powerful theranostic radiopharmaceutical for PCa.

TRIAL REGISTRATION

The clinical evaluation of this study was registered at Clinicaltrial.gov (NCT06389695) on 29 Apr, 2024.

Single-Photon Emission Computer Tomography Imaging of Prostate-Specific Membrane Antigen (PSMA) Expression in Prostate Cancer Patients Using a Novel Peptide-Based Probe [99mTc]Tc-BQ0413 with Picomolar Affinity to PSMA: A Phase I/II Clinical Study

Radionuclide imaging of prostate-specific membrane antigen (PSMA) expression can be used for staging prostate cancer. The pseudo-peptide [99mTc]Tc-BQ0413 demonstrated high affinity and specificity to PSMA in preclinical evaluation. The purpose of this study was to clinically evaluate the safety and tolerability of a single administration of [99mTc]Tc-BQ0413 as well as study its biodistribution using SPECT to estimate dosimetry. [99mTc]Tc-BQ0413 was studied in a single-center diagnostic Phase I open-label exploratory study. Whole-body planar scintigraphy and SPECT/CT imaging were performed 2, 4, and 6 h after administration of 50, 100, or 150 μg (680 ± 140 MBq) of [99mTc]Tc-BQ0413 in five PCa patients per injected mass (NCT05839990). All injections of [99mTc]Tc-BQ0413 were well tolerated. The elimination of [99mTc]Tc-BQ0413 was predominantly renal. The stable physiological uptake of [99mTc]Tc-BQ0413 was observed in the lacrimal and salivary glands, liver, spleen, and kidneys for all tested peptide-injected masses. The average effective doses were 0.007 ± 0.001, 0.0049 ± 0.0003, and 0.0062 ± 0.0008 mSv/MBq for 50, 100, and 150 μg/injection, respectively. The radionuclide-associated dose burden per patient was 4-7 mSv/study for the given activity. Uptake of [99mTc]Tc-BQ0413 in primary tumors was identified in all patients and increased with the peptide-injected mass. Uptake in lymph nodes and bone metastases was the highest at 100 μg/injected mass. The highest tumor lesion/background ratios were observed 6 h after the administration of 100 μg of [99mTc]Tc-BQ0413. The results of the Phase I study showed that injections of [99mTc]Tc-BQ0413 were well tolerated, safe, and associated with low absorbed doses. Imaging using [99mTc]Tc-BQ0413 enabled the visualization of primary prostate cancer lesions as well as metastases in lymph nodes and bones.

Real world experience with [99mTc]Tc-HYNIC-iPSMA SPECT prostate cancer detection: interim results from the global NOBLE registry

PURPOSE

[99mTc]Tc-HYNIC-iPSMA is a novel technetium-99m-labelled small molecule inhibitor of the prostate-specific membrane antigen (PSMA) for detecting prostate cancer (PC). The objective of this registry was to collect and evaluate [99mTc]Tc-HYNIC-iPSMA patient data and images to establish the safety and tolerability, and clinical utility of this agent in imaging at different stages of PC.

METHODS

Patients 18 to 80 years old with primary staging and metastatic PC were eligible. Patients unable to perform prescribed examinations, undergo a [99mTc]Tc-HYNIC-iPSMA planar and SPECT or SPECT/CT (when available), or sign a patient informed consent form were excluded from the registry. All eligible patients underwent a screening and baseline visit before imaging with [99mTc]Tc-HYNIC-iPSMA. The primary safety endpoint was assessed by collecting and grading all treatment-related adverse events using the Common Terminology Criteria for Adverse Events. Patients were followed until disease progression, death, serious or intolerable adverse events, registry termination by the sponsor, patient withdrawal, or lost to follow-up. Analysis was planned for when data was available from 40 enrolled patients.

RESULTS

40 patients enrolled in 6 countries and received [99mTc]Tc-HYNIC-iPSMA tracer administration followed by planar and SPECT imaging. Of the 40 patients included, investigators reported a change in management due to the [99mTc]Tc-HYNIC-iPSMA imaging in 17/40 of patients (42.5%). No adverse events were reported.

CONCLUSIONS

[99mTc]Tc-HYNIC-iPSMA is a promising option to identify PSMA-positive prostate cancer on SPECT and could improve patient access to PSMA imaging worldwide.

An Automated Deep Learning-Based Framework for Uptake Segmentation and Classification on PSMA PET/CT Imaging of Patients with Prostate Cancer

Uptake segmentation and classification on PSMA PET/CT are important for automating whole-body tumor burden determinations. We developed and evaluated an automated deep learning (DL)-based framework that segments and classifies uptake on PSMA PET/CT. We identified 193 [18F] DCFPyL PET/CT scans of patients with biochemically recurrent prostate cancer from two institutions, including 137 [18F] DCFPyL PET/CT scans for training and internally testing, and 56 scans from another institution for external testing. Two radiologists segmented and labelled foci as suspicious or non-suspicious for malignancy. A DL-based segmentation was developed with two independent CNNs. An anatomical prior guidance was applied to make the DL framework focus on PSMA-avid lesions. Segmentation performance was evaluated by Dice, IoU, precision, and recall. Classification model was constructed with multi-modal decision fusion framework evaluated by accuracy, AUC, F1 score, precision, and recall. Automatic segmentation of suspicious lesions was improved under prior guidance, with mean Dice, IoU, precision, and recall of 0.700, 0.566, 0.809, and 0.660 on the internal test set and 0.680, 0.548, 0.749, and 0.740 on the external test set. Our multi-modal decision fusion framework outperformed single-modal and multi-modal CNNs with accuracy, AUC, F1 score, precision, and recall of 0.764, 0.863, 0.844, 0.841, and 0.847 in distinguishing suspicious and non-suspicious foci on the internal test set and 0.796, 0.851, 0.865, 0.814, and 0.923 on the external test set. DL-based lesion segmentation on PSMA PET is facilitated through our anatomical prior guidance strategy. Our classification framework differentiates suspicious foci from those not suspicious for cancer with good accuracy.

From Oncogenesis to Theranostics: The Transformative Role of PSMA in Prostate Cancer

Prostate cancer, a leading cause of cancer-related mortality among men, is characterized by complex genetic and epigenetic alterations, dysregulation of oncogenic pathways, and a dynamic tumor microenvironment. Advances in molecular diagnostics and targeted therapies have significantly transformed the management of this disease. Prostate-specific membrane antigen (PSMA) has emerged as a critical biomarker, enhancing the precision of prostate cancer diagnosis and treatment. Theranostics, which integrates PSMA-targeted imaging with radioligand therapies, has shown remarkable efficacy in detecting and treating advanced prostate cancer. By leveraging the dual capabilities of PSMA-based diagnostics and therapeutic agents, theranostics offers a personalized approach that improves patient outcomes. This comprehensive review explores the latest developments in PSMA-targeted theranostics and their impact on the future of prostate cancer management, highlighting key clinical trials and emerging therapeutic strategies.

How to objectively evaluate the impact of image-guided surgery technologies

PURPOSE

This manuscript aims to provide a better understanding of methods and techniques with which one can better quantify the impact of image-guided surgical technologies.

METHODS

A literature review was conducted with regard to economic and technical methods of medical device evaluation in various countries. Attention was focused on applications related to image-guided interventions that have enabled procedures to be performed in a minimally invasive manner, produced superior clinical outcomes, or have become standard of care.

RESULTS

The review provides examples of successful implementations and adoption of image-guided surgical techniques, mostly in the field of neurosurgery. Failures as well as newly developed technologies still undergoing cost-efficacy analysis are discussed.

CONCLUSION

The field of image-guided surgery has evolved from solely using preoperative images to utilizing highly specific tools and software to provide more information to the interventionalist in real time. While deformations in soft tissue often preclude the use of such instruments outside of neurosurgery, recent developments in optical and radioactive guidance have enabled surgeons to better account for organ motion and provide feedback to the surgeon as tissue is cut. These technologies are currently undergoing value assessments in many countries and hold promise to improve outcomes for patients, surgeons, care teams, payors, and society in general.

Imaging at the nexus: how state of the art imaging techniques can enhance our understanding of cancer and fibrosis

Both cancer and fibrosis are diseases involving dysregulation of cell signaling pathways resulting in an altered cellular microenvironment which ultimately leads to progression of the condition. The two disease entities share common molecular pathophysiology and recent research has illuminated the how each promotes the other. Multiple imaging techniques have been developed to aid in the early and accurate diagnosis of each disease, and given the commonalities between the pathophysiology of the conditions, advances in imaging one disease have opened new avenues to study the other. Here, we detail the most up-to-date advances in imaging techniques for each disease and how they have crossed over to improve detection and monitoring of the other. We explore techniques in positron emission tomography (PET), magnetic resonance imaging (MRI), second generation harmonic Imaging (SGHI), ultrasound (US), radiomics, and artificial intelligence (AI). A new diagnostic imaging tool in PET/computed tomography (CT) is the use of radiolabeled fibroblast activation protein inhibitor (FAPI). SGHI uses high-frequency sound waves to penetrate deeper into the tissue, providing a more detailed view of the tumor microenvironment. Artificial intelligence with the aid of advanced deep learning (DL) algorithms has been highly effective in training computer systems to diagnose and classify neoplastic lesions in multiple organs. Ultimately, advancing imaging techniques in cancer and fibrosis can lead to significantly more timely and accurate diagnoses of both diseases resulting in better patient outcomes.

Bone Metastasis in Prostate Cancer: Bone Scan Versus PET Imaging

Prostate cancer is the second most common cause of malignancy among men, with bone metastasis being a significant source of morbidity and mortality in advanced cases. Detecting and treating bone metastasis at an early stage is crucial to improve the quality of life and survival of prostate cancer patients. This objective strongly relies on imaging studies. While CT and MRI have their specific utilities, they also possess certain drawbacks. Bone scintigraphy, although cost-effective and widely available, presents high false-positive rates. The emergence of PET/CT and PET/MRI, with their ability to overcome the limitations of standard imaging methods, offers promising alternatives for the detection of bone metastasis. Various radiotracers targeting cell division activity or cancer-specific membrane proteins, as well as bone seeking agents, have been developed and tested. The use of positron-emitting isotopes such as fluorine-18 and gallium-68 for labeling allows for a reduced radiation dose and unaffected biological properties. Furthermore, the integration of artificial intelligence (AI) and radiomics techniques in medical imaging has shown significant advancements in reducing interobserver variability, improving accuracy, and saving time. This article provides an overview of the advantages and limitations of bone scan using SPECT and SPECT/CT and PET imaging methods with different radiopharmaceuticals and highlights recent developments in hybrid scanners, AI, and radiomics for the identification of prostate cancer bone metastasis using molecular imaging.

Preclinical Evaluation of a Novel High-Affinity Radioligand [99mTc]Tc-BQ0413 Targeting Prostate-Specific Membrane Antigen (PSMA)

Radionuclide imaging using radiolabeled inhibitors of prostate-specific membrane antigen (PSMA) can be used for the staging of prostate cancer. Previously, we optimized the Glu-urea-Lys binding moiety using a linker structure containing 2-napththyl-L-alanine and L-tyrosine. We have now designed a molecule that contains mercaptoacetyl-triglutamate chelator for labeling with Tc-99m (designated as BQ0413). The purpose of this study was to evaluate the imaging properties of [99mTc]Tc-BQ0413. PSMA-transfected PC3-pip cells were used to evaluate the specificity and affinity of [99mTc]Tc-BQ0413 binding in vitro. PC3-pip tumor-bearing BALB/C nu/nu mice were used as an in vivo model. [99mTc]Tc-BQ0413 bound specifically to PC3-pip cells with an affinity of 33 ± 15 pM. In tumor-bearing mice, the tumor uptake of [99mTc]Tc-BQ0413 (38 ± 6 %IA/g in PC3-pip 3 h after the injection of 40 pmol) was dependent on PSMA expression (3 ± 2 %IA/g and 0.9 ± 0.3 %IA/g in PSMA-negative PC-3 and SKOV-3 tumors, respectively). We show that both unlabeled BQ0413 and the commonly used binder PSMA-11 enable the blocking of [99mTc]Tc-BQ0413 uptake in normal PSMA-expressing tissues without blocking the uptake in tumors. This resulted in an appreciable increase in tumor-to-organ ratios. At the same injected mass (5 nmol), the use of BQ0413 was more efficient in suppressing renal uptake than the use of PSMA-11. In conclusion, [99mTc]Tc-BQ0413 is a promising probe for the visualization of PSMA-positive lesions using single-photon emission computed tomography (SPECT).

PET Radiotracers in Atherosclerosis: A Review

Traditional atherosclerosis imaging modalities are limited to late stages of disease, prior to which patients are frequently asymptomatic. Positron emission tomography (PET) imaging allows for the visualization of metabolic processes underscoring disease progression via radioactive tracer, allowing earlier-stage disease to be identified. 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18F-FDG) uptake largely reflects the metabolic activity of macrophages, but is unspecific and limited in its utility. By detecting areas of microcalcification, 18F-Sodium Fluoride (18F-NaF) uptake also provides insight into atherosclerosis pathogenesis. Gallium-68 DOTA-0-Tyr3-Octreotate (68Ga-DOTATATE) PET has also shown potential in identifying vulnerable atherosclerotic plaques with high somatostatin receptor expression. Finally, 11-carbon (11C)-choline and 18F-fluoromethylcholine (FMCH) tracers may identify high-risk atherosclerotic plaques by detecting increased choline metabolism. Together, these radiotracers quantify disease burden, assess treatment efficacy, and stratify risk for adverse cardiac events.

18F-Radiolabeled Translocator Protein (TSPO) PET Tracers: Recent Development of TSPO Radioligands and Their Application to PET Study

Translocator protein 18 kDa (TSPO) is a transmembrane protein in the mitochondrial membrane, which has been identified as a peripheral benzodiazepine receptor. TSPO is generally present at high concentrations in steroid-producing cells and plays an important role in steroid synthesis, apoptosis, and cell proliferation. In the central nervous system, TSPO expression is relatively modest under normal physiological circumstances. However, some pathological disorders can lead to changes in TSPO expression. Overexpression of TSPO is associated with several diseases, such as neurodegenerative diseases, neuroinflammation, brain injury, and cancers. TSPO has therefore become an effective biomarker of related diseases. Positron emission tomography (PET), a non-invasive molecular imaging technique used for the clinical diagnosis of numerous diseases, can detect diseases related to TSPO expression. Several radiolabeled TSPO ligands have been developed for PET. In this review, we describe recent advances in the development of TSPO ligands, and ¹⁸F-radiolabeled TSPO in particular, as PET tracers. This review covers pharmacokinetic studies, preclinical and clinical trials of ¹⁸F-labeled TSPO PET ligands, and the synthesis of TSPO ligands.