Diagnostic Accuracy of PET/CT or PET/MRI Using PSMA-Targeting Radiopharmaceuticals in High-Grade Gliomas: A Systematic Review and a Bivariate Meta-Analysis

Prostate-Specific Membrane Antigen Use in Glioma Management: Past, Present, and Future

BACKGROUND

Prostate-specific membrane antigen (PSMA) is a membrane-bound metallopeptidase highly expressed in the neovasculature of many solid tumors including gliomas. It is a particularly enticing therapeutic target due to its ability to internalize, thereby delivering radioligands or pharmaceuticals to the intracellular compartment. Targeting the neovasculature of gliomas using PSMA for diagnosis and management has been a recent area of increased study and promise. The purpose of this review is to synthesize the current state and future directions of PSMA use in the histopathologic study, imaging, and treatment of gliomas.

METHODS

PubMed and Scopus databases were used to conduct a literature review on PSMA use in gliomas in June 2023. Terms searched included "PSMA," "Prostate-Specific Membrane Antigen" OR "PSMA" OR "PSMA PET" AND "glioma" OR "high grade glioma" OR "glioblastoma" OR "GBM."

RESULTS

Ninety-four publications were screened for relevance with 61 studies, case reports, and reviews being read to provide comprehensive context for the historical, contemporary, and prospective use of PSMA in glioma management.

CONCLUSIONS

PSMA PET imaging is currently a promising and accurate radiographic tool for the diagnosis and management of gliomas. PSMA histopathology likely represents a viable tool for helping predict glioma behavior. More studies are needed to investigate the role of PSMA-targeted therapeutics in glioma management, but preliminary reports have indicated its potential usefulness in treatment.

PSMA-Targeted Radiopharmaceuticals for Prostate Cancer Diagnosis and Therapy

ABSTRACT

Prostate cancer (PCa) is the most common noncutaneous malignancy in men. Until recent years, accurate imaging of men with newly diagnosed PCa, or recurrent or low-volume metastatic disease, was limited. Further, therapeutic options for men with advanced, metastatic, castration-resistant disease were increasingly limited as a result of increasing numbers of systemic therapies being combined in the upfront metastatic setting. The advent of urea-based, small-molecule inhibitors of prostate-specific membrane antigen (PSMA) has partially addressed those shortcomings in diagnosis and therapy of PCa. On the diagnostic side, there are multiple pivotal phase III trials with several different agents having demonstrated utility in the initial staging setting, with generally modest sensitivity but very high specificity for determining otherwise-occult pelvic nodal involvement. That latter statistic drives the utility of the scan by allowing imaging interpreters to read with very high sensitivity while maintaining a robust specificity. Other pivotal phase III trials have demonstrated high detection efficiency in patients with biochemical failure, with high positive predictive value at the lesion level, opening up possible new avenues of therapy such as metastasis-directed therapy. Beyond the diagnostic aspects of PSMA-targeted radiotracers, the same urea-based chemical scaffolds can be altered to deliver therapeutic isotopes to PCa cells that express PSMA. To date, one such agent, when combined with best standard-of-care therapy, has demonstrated an ability to improve overall survival, progression-free survival, and freedom from skeletal events relative to best standard-of-care therapy alone in men with metastatic, castration-resistant PCa who are post chemotherapy. Within the current milieu, there are a number of important future directions including the use of artificial intelligence to better leverage diagnostic findings, further medicinal chemistry refinements to the urea-based structure that may allow improved tumor targeting and decreased toxicities, and the incorporation of new radionuclides that may better balance efficacy with toxicities than those nuclides that are available.

Diagnostic Accuracy of PET with 18F-Fluciclovine ([18F]FACBC) in Detecting High-Grade Gliomas: A Systematic Review and Meta-Analysis

BACKGROUND

18F-Fluciclovine ([18F]FACBC) has been recently proposed as a synthetic radiolabeled amino acid for positron emission tomography (PET) imaging in patients with brain neoplasms. Our aim is to evaluate the diagnostic performance of [18F]FACBC PET in high-grade glioma (HGG) patients, taking into account the literature data.

METHODS

A comprehensive literature search was performed. We included original articles evaluating [18F]FACBC PET in the detection of HGG before therapy and for the suspicion of tumor recurrence. Pooled sensitivity, specificity, positive and negative likelihood ratios (LR+ and LR-), and diagnostic odds ratios (DOR), including 95% confidence intervals (95% CI), were measured. Statistical heterogeneity and publication bias were also assessed.

RESULTS

ten studies were included in the review and eight in the meta-analysis (113 patients). Regarding the identification of HGG, the sensitivity of [18F]FACBC PET ranged between 85.7% and 100%, with a pooled estimate of 92.9% (95% CI: 84.4-96.9%), while the specificity ranged from 50% to 100%, with a pooled estimate of 70.7% (95% CI: 47.5-86.5%). The pooled LR+, LR-, and DOR of [18F]FACBC PET were 2.5, 0.14, and 37, respectively. No significant statistical heterogeneity or publication bias were found.

CONCLUSIONS

evidence-based data demonstrate the good diagnostic accuracy of [18F]FACBC PET for HGG detection. Due to the still limited data, further studies are warranted to confirm the promising role of [18F]FACBC PET in this context.

PSMA PET/CT in Castration-Resistant Prostate Cancer: Myth or Reality?

BACKGROUND

prostate-specific membrane antigen (PSMA) ligand PET has been recently incorporated into international guidelines for several different indications in prostate cancer (PCa) patients. However, there are still some open questions regarding the role of PSMA ligand PET in castration-resistant prostate cancer (CRPC). The aim of this work is to assess the clinical value of PSMA ligand PET/CT in patients with CRPC.

RESULTS

PSMA ligand PET has demonstrated higher detection rates in comparison to conventional imaging and allows for a significant reduction in the number of M0 CRPC patients. However, its real impact on patients' prognosis is still an open question. Moreover, in CRPC patients, PSMA ligand PET presents some sensitivity and specificity limitations. Due to its heterogeneity, CRPC may present a mosaic of neoplastic clones, some of which could be PSMA-/FDG+, or vice versa. Likewise, unspecific bone uptake (UBU) and second primary neoplasms (SNPs) overexpressing PSMA in the neoangiogenic vessels represent potential specificity issues. Integrated multi-tracer imaging (PSMA ligand and [18F]FDG PET) together with a multidisciplinary discussion could allow for reaching the most accurate evaluation of each patient from a precision medicine point of view.

Neuro-Oncology and Positron Emission Tomography: "Just Can't Get Enough"

Imaging has a pivotal role in neuro-oncology for the management of primary and secondary brain tumors [...].

Discriminating Inflammatory Radiation-Related Changes From Early Recurrence in Patients With Glioblastomas: A Preliminary Analysis of 68Ga-PSMA-11 PET/CT Compared With 18F-FDOPA PET/CT

PURPOSE OF THE REPORT

Using morphological and functional imaging to discriminate recurrence from postradiation-related modifications in patients with glioblastomas remains challenging. This pilot study aimed to assess the feasibility of using 68Ga-prostate-specific membrane antigen (PSMA) 11 PET/CT compared with 18F-FDOPA PET/CT to detect early recurrence.

METHODS

Nine patients followed up for glioblastomas who received MRI during 12 months of follow-up were referred for both 68Ga-PSMA-11 and 18F-FDOPA PET/CT. The SUVmax, lesion-to-striatum ratio, lesion-to-normal parenchyma ratio, and lesion-to-salivary gland ratio were calculated.

RESULTS

Good correlation between 18F-FDOPA and 68Ga-PSMA PET/CT findings was seen in 5 patients. In 4 patients, the findings of both examinations were consistent with recurrence but were better visualized with the PSMA PET/CT. Examinations of the fifth patient were suggestive of postradiation-related changes and were better analyzed with the PSMA PET/CT, which displayed relatively low uptake compared with DOPA PET/CT. Conversely, 4 patients showed conflicting results: recurrence was not detected on the PSMA PET/CT because of previously introduced bevacizumab treatment; in another patient, both examinations were consistent with recurrence, but there was an uptake mismatch at the suspected lesion sites, and 2 patients presented with inconsistent findings.

CONCLUSIONS

Despite a few discrepancies, this study highlights the potential role of 68Ga-PSMA-11 PET/CT for discriminating postradiation inflammation from recurrence. 68Ga-PSMA-11 PET/CT has an excellent lesion-to-background ratio, and false-positive and false-negative results could be minimized through implementing certain protocols before performing the examination. More powerful prospective studies are required to validate our results.

Can PSMA-Targeting PET/CT Be a Valuable Instrument to Assess the Presence of Brain Metastases in Lung Cancer Patients?: A Case Report

ABSTRACT

A 78-year-old man with synchronous diagnosis of prostate cancer and lung adenocarcinoma was referred to our institute for prostate cancer staging with [ 18 F]F-prostate-specific membrane antigen (PSMA) 1007 PET/CT. In addition to the previously known lesion of the right lung, PSMA-targeted PET/CT highlighted 2 areas of abnormal uptake in the brain, in the left frontal and temporal lobes. A subsequent MRI confirmed the lesions observed on PET/CT. Because PSMA-targeting radiopharmaceuticals do not accumulate in healthy brain parenchyma, and recent literature reported promising performances of PSMA-targeted PET/CT in gliomas and metastases from tumors other than prostate cancer, this employment of PSMA radioligands needs to be further explored.

Potential Role of PSMA-Targeted PET in Thyroid Malignant Disease: A Systematic Review

BACKGROUND

Recently, several studies introduced the potential use of positron emission tomography/computed tomography (PET/CT) with prostate-specific membrane antigen (PSMA)-targeting radiopharmaceuticals in radioiodine-refractory thyroid cancer (TC).

METHODS

The authors accomplished a comprehensive literature search of original articles concerning the performance of PSMA-targeted PET/CT in TC patients. Original papers exploring this molecular imaging examination in radioiodine-refractory TC patients undergoing restaging of their disease were included.

RESULTS

A total of 6 documents concerning the diagnostic performance of PSMA-targeted PET/CT in TC (49 patients) were included in this systematic review. The included articles reported heterogeneous values of PSMA-targeted PET/CT detection rates in TC, ranging from 25% to 100% and overall inferior to [¹⁸F]-fluorodeoxyglucose PET/CT when the two molecular imaging examinations were compared. Two studies reported the administration of [¹⁷⁷Lu]PSMA-radioligands with theragnostic purpose in three patients.

CONCLUSIONS

The available literature data in this setting are limited and heterogeneous. The employment of PET with PSMA-targeting radiopharmaceuticals in this setting did not affect patient management. Nevertheless, prospective multicentric studies are needed to properly assess its potential role in TC patients.

PCBP2 Reduced Oxidative Stress-Induced Apoptosis in Glioma through cGAS/STING Pathway by METTL3-Mediated m6A Modification

Purpose

The most prevalent primary malignant tumor of CNS is glioma, which has a dismal prognosis. The theory of oxidative stress is one of the important theories in the study of its occurrence and development mechanism. In this study, the impacts of PCBP2 on glioma sufferers and the possible mechanisms were examined.

Methods

Patients with glioma were obtained from May 2017 to July 2018. Quantitative PCR, microarray analysis, western blot analysis, and immunofluorescence were used in this experiment.

Results

PCBP2 mRNA expression level and protein expression in patients with glioma were upregulated compared with paracancerous tissue. OS and DFS of PCBP2 low expression in patients with glioma were higher than those of PCBP2 high expression. PCBP2 promoted the progression and metastasis of glioma. PCBP2 reduced oxidative stress-induced apoptosis of glioma. PCBP2 suppressed the cGAS/STING pathway of glioma. PCBP2 protein interlinked with cGAS and cGAS was one target for PCBP2. METTL3-mediated m6A modification increases PCBP2 stability.

Conclusion

Along the cGAS-STING signal pathway, PCBP2 decreased the apoptosis that oxidative stress-induced glioma caused, which might be a potential target to suppress oxidative stress-induced apoptosis of glioma.