Intraindividual Comparison of 18F-PSMA-1007 with Renally Excreted PSMA Ligands for PSMA PET Imaging in Patients with Relapsed Prostate Cancer

The superior detection rate of total-body [68Ga]Ga-PSMA-11 PET/CT compared to short axial field-of-view [68Ga]Ga-PSMA-11 PET/CT for early recurrent prostate cancer patients with PSA < 0.2 ng/mL after radical prostatectomy

BACKGROUND AND PURPOSE

[68Ga]Ga-PSMA PET imaging has been extensively utilized for the detection of biochemical recurrence (BCR) in prostate cancer. However, the detection rate declines to merely 10-40% when PSA levels are < 0.2 ng/mL employing short axial field-of-view (SAFOV) PET. Prior studies exhibited superior detection rates with total-body [68Ga]Ga-PSMA-11 PET compared to SAFOV [68Ga]Ga-PSMA-11 PET in BCR patients with PSA > 0.2 ng/mL. Nevertheless, the diagnostic utility of total-body [68Ga]Ga-PSMA-11 PET for BCR patients when PSA is < 0.2 ng/mL remains unclear. This study aimed to assess whether total-body [68Ga]Ga-PSMA-11 PET/CT could improve the detection rate compared to SAFOV [68Ga]Ga-PSMA-11 PET/CT in BCR patients with PSA < 0.2 ng/mL.

METHODS

Eighty BCR patients with PSA < 0.2 ng/mL underwent total-body [68Ga]Ga-PSMA-11 PET/CT. These patients were matched by baseline qualities to another 80 patients who received SAFOV [68Ga]Ga-PSMA-11 PET/CT. The detection rates of total-body [68Ga]Ga-PSMA-11 PET/CT and SAFOV [68Ga]Ga-PSMA-11 PET/CT were compared utilizing a chi-square test and stratified analysis. Image quality of total-body [68Ga]Ga-PSMA PET/CT and SAFOV [68Ga]Ga-PSMA-11 PET/CT was assessed based on subjective scoring and objective parameters. The objective parameters measured were SUVmax, SUVmean, standard deviation (SD) of SUV, and signal-to-noise ratio (SNR) of liver and gluteus maximus.

RESULTS

The image quality of total-body [68Ga]Ga-PSMA PET/CT was superior to that of SAFOV [68Ga]Ga-PSMA-11 PET/CT in both early and delayed scans. The detection rate of total-body [68Ga]Ga-PSMA PET/CT for BCR patients with PSA < 0.2 ng/mL was significantly higher than that of SAFOV [68Ga]Ga-PSMA-11 PET/CT (73.75% vs. 43.75%, P < 0.001). Total-body [68Ga]Ga-PSMA PET/CT resulted in noteworthy modifications to the treatment regimen when contrasted with SAFOV [68Ga]Ga-PSMA-11 PET/CT.

CONCLUSIONS

In BCR patients with PSA < 0.2 ng/mL, total-body [68Ga]Ga-PSMA-11 PET/CT not only demonstrated a significantly higher detection rate compared to SAFOV [68Ga]Ga-PSMA-11 PET/CT but also led to significant alterations in treatment regimens.

Diagnostic Accuracy of 18F-Prostate Specific Membrane Antigen (PSMA) PET/CT Radiotracers in Staging and Restaging of Patients With High-Risk Prostate Cancer or Biochemical Recurrence: An Overview of Reviews

The aim of this overview was to consolidate existing evidence syntheses and provide a comprehensive overview of the evidence for 18F-prostate specific membrane antigen (PSMA) PET/CT in the staging of high-risk prostate cancer and restaging after biochemical recurrence. An overview of reviews was performed and reported in line with the preferred reporting items for overview of reviews (PRIOR) statement and synthesis without meta-analysis (SWiM) reporting guidelines. A comprehensive database and grey literature search were conducted up to July 18, 2023. Systematic reviews were assessed using the risk of bias in systematic reviews (ROBIS) tool. The certainty of the evidence was assessed using grading of recommendations, assessment, development and evaluations (GRADE). 11 systematic reviews were identified; 10 were at high or unclear risk of bias. Evidence reported on a per-patient, per-lymph node, and per-lesion basis for sensitivity, specificity and overall accuracy was identified. There was a lack of data on dose, adverse events and evidence directly comparing 18F-PSMA PET/CT to other imaging modalities. Evidence with moderate to very low certainty indicated high sensitivity, specificity and accuracy of 18F-PSMA PET/CT in patients with high-risk prostate cancer and biochemical recurrence. There was considerably lower certainty evidence and greater variability in effect estimates for outcomes for the combined intermediate/high-risk cohort. While evidence gaps remain for some outcomes, and most systematic reviews were at high or unclear risk of bias, the current evidence base is broadly supportive of 18F-PSMA PET/CT imaging in the staging and restaging of patients with high-risk prostate cancer and biochemical recurrence.

The Homunculus of unspecific bone uptakes associated with PSMA-targeted tracers: a systematic review-based definition

PURPOSE

Prostate-Specific Membrane Antigen (PSMA)-targeted Positron Emission Tomography (PET) has revolutionised prostate cancer (PCa) diagnosis and treatment, offering superior diagnostic accuracy over traditional methods and enabling theragnostic applications. However, a significant diagnostic challenge has emerged with identifying unspecific bone uptakes (UBUs), which could lead to over-staging and inappropriate treatment decisions if misinterpreted. This systematic review explores the phenomenon of UBUs in PCa patients undergoing PSMA-PET imaging.

METHODS

Studies assessing the prevalence, topographical distribution, and potential clinical implications of UBUs were selected according to the Preferred Reporting Items for a Systematic Review and Meta-Analysis (PRISMA) method and evaluated with the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool.

RESULTS

The percentage of PCa patients with UBUs on PSMA-PET scans ranged from 0 to 71.7%, depending on the radiopharmaceutical used, with [18F]PSMA-1007 showing the highest incidence. The ribs are the primary site of UBUs across all PSMA-targeted radiopharmaceuticals. The spine is the second most frequent UBU site for [68Ga]Ga-PSMA-11, [18F]DCFPyL, [18F]rhPSMA-7, while the pelvic girdle represents the second most frequent site for [18F]PSMA-1007. The average maximum Standardized Uptake Value (SUVmax) of UBUs varied from 3.4 to 7.7 and was generally lower than that of bone metastases.

CONCLUSIONS

Our findings underscore the need for heightened awareness and precise interpretation of UBUs to avoid potential over-staging and subsequent inappropriate treatment decisions. Considering the radiopharmaceutical used, PET-derived semiquantitative parameters, the topographical distribution of UBUs, and accurately evaluating the pre-test probability based on clinical and laboratory parameters may aid nuclear medicine physicians in interpreting PSMA-PET findings.

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.

Fluorine-18 prostate-specific membrane antigen-1007-avid indeterminate bone lesions in prostate cancer: clinical and PET/CT features to predict outcomes and prognosis

AIM

To determine clinical and fluorine-18 prostate-specific membrane antigen-1007 (18F-PSMA-1007) integrated positron-emission tomography (PET)/computed tomography (CT) features that could be used to interpret indeterminate bone lesions (IBLs) and assess the prognosis of prostate cancer (PCa) in patients with IBLs.

MATERIALS AND METHODS

Consecutive patients who underwent PSMA PET/CT were analysed retrospectively. IBLs were identified as benign or malignant based on follow-up imaging and clinical management. Lesion- and patient-based assessments were performed to define features predictive of bone lesion results and determine clinical risk. Patients' prognosis was analysed based on clinical characteristics, including prostate-specific antigen (PSA) and alkaline phosphatase (ALP), respectively.

RESULTS

A total of 105 patients (mean age ± SD, 72.1 ± 8 years) were evaluated and 158 IBLs were identified. Fifty-three (33.5%), 36 (22.8%), and 69 (43.7%) IBLs were benign, malignant, and equivocal, respectively. Variables including location, maximum standard uptake value (SUVmax), and lymph node metastases (LNM) were related to the benignancy or malignancy of IBLs (p=0.046, p<0.001 and p<0.001, respectively). Regression analysis indicated that LNM, SUVmax, and location of IBLs could be predictors of lesion interpretation (p<0.001, p=0.002 and p=0.035). Patients with benign IBLs experienced the most considerable decreases in PSA and ALP levels.

CONCLUSIONS

LNM, SUVmax, and location may contribute to IBL interpretation. A rapid decrease in PSA and ALP levels might suggest a better prognosis for patients with benign IBLs.

Evaluating the biodistribution for [68Ga]Ga-PSMA-11 and [18F]F-PSMA-1007 PET/CT with an inter- and intrapatient based analysis

BACKGROUND

Liver uptake in [68Ga]Ga-PSMA-11 PET is used as an internal reference in addition to clinical parameters to select patients for [177Lu]Lu-PSMA-617 radioligand therapy (RLT). Due to increased demand, [68Ga]Ga-PSMA-11 was replaced by [18F]F-PSMA-1007, a more lipophilic tracer with different biodistribution and splenic uptake was suggested as a new internal reference. We compared the intra-patient tracer distribution between [68Ga]Ga-PSMA-11 and [18F]F-PSMA-1007.

METHODS

Fifty patients who underwent PET examinations in two centers with both [18F]F-PSMA-1007 and [68Ga]Ga-PSMA-11 within one year were included. Mean standardized uptake values (SUVmean) were obtained for liver, spleen, salivary glands, blood pool, and bone. Primary tumor, local recurrence, lymph node, bone or visceral metastasis were also assessed for intra- and inter-individual comparison.

RESULTS

Liver SUVmean was significantly higher with [18F]F-PSMA-1007 (11.7 ± 3.9) compared to [68Ga]Ga-PSMA-11 (5.4 ± 1.7, p < .05) as well as splenic SUVmean (11.2 ± 3.5 vs.8.1 ± 3.5, p < .05). The blood pool was comparable between the two scans. Malignant lesions did not show higher SUVmean on [18F]F-PSMA-1007. Intra-individual comparison of liver uptake between the two scans showed a linear association for liver uptake with SUVmean [68Ga]Ga-PSMA-11 = 0.33 x SUVmean [18F]F-PSMA-1007 + 1.52 (r = .78, p < .001).

CONCLUSION

Comparing biodistribution of [68Ga]Ga and [18F]F tracers, liver uptake on [68Ga]Ga-PSMA-11 PET is the most robust internal reference value. Liver uptake of [18F]F-PSMA-1007 was significantly higher, but so was the splenic uptake. The strong intra-individual association of hepatic accumulation between the two scans may allow using of a conversion factor for [18F]F-PSMA-1007 as a basis for RLT selection.

Dependence of Renal Uptake on Kidney Function in [68Ga]Ga-PSMA-11 PET/CT Imaging

(1) Background: PSMA ligand PET/CT is increasingly important for diagnostics of prostate cancer and other tumor diseases. In particular, the radiopharmaceutical [68Ga]Ga-PSMA-11 is widely used. Besides its tumor-specific binding, the uptake within the kidneys is dominant and seems to visualize the renal cortex specifically. Kidney diseases may alter the uptake of radiopharmaceuticals. Therefore, the correlation between renal uptake in PET/CT imaging and renal function should be investigated. (2) Methods: A group of 103 male patients were retrospectively evaluated for eGFR according to the CKD-EPI equation, tracer uptake intensity (SUVmax, SUVpeak, SUVmean), the molecular volume of the renal cortex, morphological kidney size, and total renal uptake. Manual and three different computer-assisted contouring methods (thresholds at 50% of SUVmax, 30% of SUVmax, and absolute SUV of 20) were used for measurements. Correlations between parameters were calculated using linear regression models. (3) Results: Renal SUVmax, SUVpeak, and SUVmean do not correlate with eGFR for manual or computer-assisted measurements. In contrast, molecular cortex volume shows a moderate correlation with eGFR (R2 = 0.231, p < 0.001), superior to morphological kidney size. A contouring threshold of 30% of SUVmax outperformed the other settings for renal cortex volume and total renal uptake. (4) Conclusions: Renal uptake of [68Ga]Ga-PSMA-11 cannot predict eGFR, but the functional renal cortex can be quantified by PET/CT imaging.

Radiotheranostics in advanced prostate cancer: Current and future directions

The discovery of small molecules that target the extracellular domain of prostate-specific membrane antigen (PSMA) has led to advancements in diagnostic imaging and the development of precision radiopharmaceutical therapies. In this review, we present the available existing data and highlight the key ongoing clinical evaluations of PSMA-based imaging in the management of primary, biochemically recurrent, and metastatic prostate cancer. We also discuss clinical studies that explore the use of PSMA-based radiopharmaceutical therapy (RPT) in metastatic prostate cancer and forthcoming trials that investigate PSMA RPT in earlier disease states. Multidisciplinary collaboration in clinical trial design and therapeutic administration is critical to the continued progress of this evolving radiotheranostics field.

Clinical value of 18F-PSMA-1007 PET/MRI in primary staging of patients with intermediate- to high-risk prostate cancer

OBJECTIVE

To assess the utility of 18F-PSMA-1007 PET/MRI in initial staging of intermediate- to high-risk prostate cancer (HRPCa).

METHODS

A total of 46 patients with pathologically verified intermediate and/or HRPCa who underwent 18F-PSMA-1007 PET/MRI with dedicated pelvic high-resolution multiparametric MRI (mpMRI) were included.

RESULTS

PET/MRI showed 100% sensitivity (SN), specificity (SP), positive predictive value (PPV), negative predictive value (NPV), and accuracy in detecting seminal vesicle (SV) and rectal invasion, versus 87.5%, 100%, 100% 93.8%, 95.7% and 50%, 100%,100%, 95.5%, and 95.7% for mpMRI respectively. However, PET/MRI had poor SN (40% and 0%) but high SP (94.4% and 100%) in detection of UB and neurovascular bundle (NV) invasion compared to 100% SN and SP for mpMRI. PET/MRI demonstrated stronger TNM staging agreement with the gold standard than mpMRI-WBMRI. It demonstrated concordance with T, N, and M stages in 40, 41, and 36 patients (k 0.84, 0.60, and 0.68, respectively) versus 29, 33, and 31 patients (k 0.54, 0.22, and 0.50) with accurate over all staging of 38/46 patients versus 30/46 patients (K 0.52 versus 0.22).

CONCLUSION

18F-PSMA-1007 PET/MRI is a promising imaging modality with high diagnostic accuracy in staging intermediate- and HRPCa; it improves local tumour evaluation and provides precise TNM staging.

ADVANCES IN KNOWLEDGE

18F-PSMA-1007 PET/MRI could have high diagnostic accuracy as shown in the current study for staging HRPCa patients that is crucial for treatment selection. We think that our study will contribute to the body of knowledge and improve the literature surrounding the clinical uses of integrated 18F-PSMA-1007 PET/MRI.

The Impact of Positron Emission Tomography Imaging and Tumor Molecular Profiling on Risk Stratification, Treatment Choice, and Oncological Outcomes of Patients with Primary or Relapsed Prostate Cancer: An International Collaborative Review of the Existing Literature

CONTEXT

The clinical introduction of next-generation imaging methods and molecular biomarkers ("radiogenomics") has revolutionized the field of prostate cancer (PCa). While the clinical validity of these tests has thoroughly been vetted, their clinical utility remains a matter of investigation.

OBJECTIVE

To systematically review the evidence to date on the impact of positron emission tomography (PET) imaging and tissue-based prognostic biomarkers, including Decipher, Prolaris, and Oncotype Dx, on the risk stratification, treatment choice, and oncological outcomes of men with newly diagnosed PCa or those with biochemical failure (BCF).

EVIDENCE ACQUISITION

We performed a quantitative systematic review of the literature using the MEDLINE, EMBASE, and Web of Science databases (2010-2022) following the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement guidelines. The validated Quality Assessment of Diagnostic Accuracy Studies 2 scoring system was used to assess the risk of bias.

EVIDENCE SYNTHESIS

A total of 148 studies (130 on PET and 18 on biomarkers) were included. In the primary PCa setting, prostate-specific membrane antigen (PSMA) PET imaging was not useful in improving T staging, moderately useful in improving N staging, but consistently useful in improving M staging in patients with National Comprehensive Cancer Network (NCCN) unfavorable intermediate- to very-high-risk PCa. Its use led to a management change in 20-30% of patients. However, the effect of these treatment changes on survival outcomes was not clear. Similarly, biomarkers in the pretherapy primary PCa setting increased and decreased the risk, respectively, in 7-30% and 32-36% of NCCN low-risk and 31-65% and 4-15% of NCCN favorable intermediate-risk patients being considered for active surveillance. A change in management was noted in up to 65% of patients, with the change being in line with the molecular risk-based reclassification, but again, the impact of these changes on survival outcomes remained unclear. Notably, in the postsurgical primary PCa setting, biomarker-guided adjuvant radiation therapy (RT) was associated with improved oncological control: Δ↓ 2-yr BCF by 22% (level 2b). In the BCF setting, the data were more mature. PSMA PET was consistently useful in improving disease localization-Δ↑ detection for T, N, and M staging was 13-32%, 19-58%, and 9-29%, respectively. Between 29% and 73% of patients had a change in management. Most importantly, these management changes were associated with improved survival outcomes in three trials: Δ↑ 4-yr disease-free survival by 24.3%, Δ↑ 6-mo metastasis-free survival (MFS) by 46.7%, and Δ↑ androgen deprivation therapy-free survival by 8 mo in patients who received PET-concordant RT (level 1b-2b). Biomarker testing in these patients also appeared to be helpful in risk stratifying and guiding the use of early salvage RT (sRT) and concomitant hormonal therapy. Patients with high-genomic-risk scores benefitted from treatment intensification: Δ↑ 8-yr MFS by 20% with the use of early sRT and Δ↑ 12-yr MFS by 11.2% with the use of hormonal therapy alongside early sRT, while low-genomic-risk score patients did equally well with initial conservative management (level 3).

CONCLUSIONS

Both PSMA PET imaging and tumor molecular profiling provide actionable information in the management of men with primary PCa and those with BCF. Emerging data suggest that radiogenomics-guided treatments translate into direct survival benefits for patients, however, additional prospective data are awaited.

PATIENT SUMMARY

In this review, we evaluated the utility of prostate-specific membrane antigen positron emission tomography and tumor molecular profiling in guiding the care of men with prostate cancer (PCa). We found that these tests augmented risk stratification, altered management, and improved cancer control in men with a new diagnosis of PCa or for those experiencing a relapse.

A Practical Guide to the Pearls and Pitfalls of PSMA PET Imaging

Prostate-specific membrane antigen (PSMA)-targeted PET agents have revolutionized the care of patients with prostate cancer, supplanting traditional methods of imaging prostate cancer, and improving the selection and delivery of therapies. This has led to a rapid expansion in both the number of PSMA PET scans performed and the imaging specialists required to interpret those scans. To aid those imagers and clinicians who are new to the interpretation of PSMA PET, this review provides an overview of the interpretation of PSMA PET/CT imaging and pearls for overcoming commonly encountered pitfalls. We discuss the physiologic distribution of the clinically available PSMA-targeted radiotracers, the commonly encountered patterns of prostate cancer spread, as well as the benign and malignant mimics of prostate cancer. Additionally, we review the standardized PSMA PET reporting systems and the role of PSMA in selecting appropriate patients for PSMA-targeted therapies.

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.

Diagnostic performance of 18F-labeled PSMA PET/CT in patients with biochemical recurrence of prostate cancer: a systematic review and meta-analysis

BACKGROUND

After initial treatment of prostate cancer, increases in prostate-specific antigen (PSA) levels commonly signify potential relapse or metastasis. 18F-labeled prostate-specific membrane antigen (PSMA) is considered a promising treatment due to its favorable physical properties.

PURPOSE

To investigate the diagnostic value of 18F-PSMA PET/CT for the recurrence and/or metastasis of biochemical recurrence of prostate cancer (BRPca).

MATERIAL AND METHODS

A comprehensive literature search was conducted in PubMed, EMBASE, Web of Science, and the Cochrane Library databases. Combined sensitivity and specificity values for the use of 18F-PSMA PET/CT in patients with BRPca were obtained. The quality of the studies was tested using the Diagnostic Accuracy Research Quality Assessment tool. Meta-analysis was performed using STATA 15 software, and heterogeneity was subsequently tested.

RESULTS

A total of 16 studies (1162 patients) were enrolled and had significant heterogeneity. The pooled sensitivity, specificity, and AUC values for 18F-PSMA PET/CT in the diagnosis of prostate recurrence and/or metastasis were 0.93 (0.89-0.95), 0.94 (0.85-0.98), and 0.96 (0,94-0.98), respectively. Meta-regression analyses showed that the sources of heterogeneity did not relate to ligands, study designs, or participants. The pooled sensitivity and specificity values of 18F-DCFPyL PET/CT were 0.90 (0.85-0.94) and 0.89 (0.85-0.93), respectively. The pooled sensitivity and specificity values of 18F-PSMA-1007 PET/CT were 0.89 (0.85-0.93) and 0.93 (0.70-0.99), respectively. The per-patient pooled sensitivity and specificity values were 0.92 (0.86-0.96) and 0.83 (0.41-0.97), respectively. The per-lesion pooled sensitivity and specificity values were 0.91 (0.86-0.94) and 0.91 (0.86-0.94), respectively.

CONCLUSION

According to our meta-analysis, 18F-PSMA PET/CT has the potential to be critical for the diagnosis of recurrence and/or metastasis in patients with BRPca.

Threshold for defining PSMA-positivity prior to 177Lu-PSMA therapy: a comparison of [68Ga]Ga-PSMA-11 and [18F]F-DCFPyL in metastatic prostate cancer

BACKGROUND

In 2022, the American Food and Drug Administration and the European Medicines Agency approved [177Lu]Lu-PSMA-617 (PLUVICTO™, Novartis AG, Basel, Switzerland) for radionuclide therapy with prostate-specific membrane antigen (PSMA) ligands in metastatic prostate cancer. Theranostics require appropriate patients to be identified by positron emission tomography (PET) prior to radionuclide therapy, usually employing [68Ga]Ga-PSMA-11. Alternatively, several 18F-labelled PSMA-PET tracers are available and may increasingly replace 68Ga-labelled compounds, with respect to their image quality, availability and other practical advantages. However, alternative tracers may differ in uptake behaviour, and their comparability with regard to patient selection for [177Lu]Lu-PSMA therapy has not yet been established. Here, we analysed whether tumour-to-background ratios determined by PET using the 18F-labelled PSMA-specific radiopharmaceutical [18F]F-DCFPyL were comparable to those determined by PET using [68Ga]Ga-PSMA-11.

RESULTS

No differences could be observed between [68Ga]Ga-PSMA-11-PET and [18F]F-DCFPyL-PET regarding tumour-to-liver ratios or tumour-to-mediastinum ratios (e. g. tumour-to-liver ratios using maximum SUV of the tumour lesion for ultra-high definition reconstructed PET images with a median of 2.5 (0.6-9.0) on [68Ga]Ga-PSMA-11-PET vs. 2,0 (0.6-11.4) on [18F]F-DCFPyL-PET). However, significant differences were observed in terms of contrast-to-noise ratios, thereby demonstrating the better image quality obtained with [18F]F-DCFPyL-PET.

CONCLUSIONS

Our data showed that [18F]F-DCFPyl-PET and [68Ga]Ga-PSMA-11-PET provide comparable tumour-to-liver and tumour-to-mediastinum ratios. Therefore, a tumour uptake of [18F]F-DCFPyL above the liver background, like using [68Ga]Ga-PSMA-11, can be considered as equally suitable for defining PSMA-positivity by a semiquantitative assessment based on the liver background, e. g. prior to radioligand therapy with 177Lu-labelled PSMA ligands. In addition, our data suggest a tending advantage of [18F]F-DCFPyL in terms of lesion detectability.

Management of Patients with Advanced Prostate Cancer. Part I: Intermediate-/High-risk and Locally Advanced Disease, Biochemical Relapse, and Side Effects of Hormonal Treatment: Report of the Advanced Prostate Cancer Consensus Conference 2022

BACKGROUND

Innovations in imaging and molecular characterisation and the evolution of new therapies have improved outcomes in advanced prostate cancer. Nonetheless, we continue to lack high-level evidence on a variety of clinical topics that greatly impact daily practice. To supplement evidence-based guidelines, the 2022 Advanced Prostate Cancer Consensus Conference (APCCC 2022) surveyed experts about key dilemmas in clinical management.

OBJECTIVE

To present consensus voting results for select questions from APCCC 2022.

DESIGN, SETTING, AND PARTICIPANTS

Before the conference, a panel of 117 international prostate cancer experts used a modified Delphi process to develop 198 multiple-choice consensus questions on (1) intermediate- and high-risk and locally advanced prostate cancer, (2) biochemical recurrence after local treatment, (3) side effects from hormonal therapies, (4) metastatic hormone-sensitive prostate cancer, (5) nonmetastatic castration-resistant prostate cancer, (6) metastatic castration-resistant prostate cancer, and (7) oligometastatic and oligoprogressive prostate cancer. Before the conference, these questions were administered via a web-based survey to the 105 physician panel members ("panellists") who directly engage in prostate cancer treatment decision-making. Herein, we present results for the 82 questions on topics 1-3.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Consensus was defined as ≥75% agreement, with strong consensus defined as ≥90% agreement.

RESULTS AND LIMITATIONS

The voting results reveal varying degrees of consensus, as is discussed in this article and shown in the detailed results in the Supplementary material. The findings reflect the opinions of an international panel of experts and did not incorporate a formal literature review and meta-analysis.

CONCLUSIONS

These voting results by a panel of international experts in advanced prostate cancer can help physicians and patients navigate controversial areas of clinical management for which high-level evidence is scant or conflicting. The findings can also help funders and policymakers prioritise areas for future research. Diagnostic and treatment decisions should always be individualised based on patient and cancer characteristics (disease extent and location, treatment history, comorbidities, and patient preferences) and should incorporate current and emerging clinical evidence, therapeutic guidelines, and logistic and economic factors. Enrolment in clinical trials is always strongly encouraged. Importantly, APCCC 2022 once again identified important gaps (areas of nonconsensus) that merit evaluation in specifically designed trials.

PATIENT SUMMARY

The Advanced Prostate Cancer Consensus Conference (APCCC) provides a forum to discuss and debate current diagnostic and treatment options for patients with advanced prostate cancer. The conference aims to share the knowledge of international experts in prostate cancer with health care providers and patients worldwide. At each APCCC, a panel of physician experts vote in response to multiple-choice questions about their clinical opinions and approaches to managing advanced prostate cancer. This report presents voting results for the subset of questions pertaining to intermediate- and high-risk and locally advanced prostate cancer, biochemical relapse after definitive treatment, advanced (next-generation) imaging, and management of side effects caused by hormonal therapies. The results provide a practical guide to help clinicians and patients discuss treatment options as part of shared multidisciplinary decision-making. The findings may be especially useful when there is little or no high-level evidence to guide treatment decisions.

Multi-timepoint imaging with PSMA-targeted [18F]F-Florastamin PET/CT: lesion detection and comparison to conventional imaging

OBJECTIVE

The aims of this study were to investigate the utility of [¹⁸F]F-Florastamin, a novel prostate-specific membrane antigen (PSMA)-targeted PET radiotracer with facile radiochemistry, relative to the conventional imaging for the detection of sties of disease and evaluate the effect of multi-timepoint imaging with [¹⁸F]F-Florastamin PET on lesion detectability.

METHODS

Eight prostate cancer patients with known or suspected recurrence who underwent [¹⁸F]F-Florastamin PET/CT at 1-h and 2-h imaging time-points were included in this prospective pilot study. [¹⁸F]F-Florastamin PET images were interpreted visually and quantitatively at both time points and compared with CIM.

RESULTS

[¹⁸F]F-Florastamin PET was superior to CT in the detection of active osseous metastases and small-sized metastatic lymph nodes that do not fall under the anatomic imaging size criteria for metastasis. Multi-timepoint imaging showed a significant reduction in the blood pool, bone marrow and muscular uptake, and increase in liver uptake over time. There is a significant improvement in tumor-to-background ratio (TBR) at the 2-h imaging time-point (P = 0.04). The mean percentage change in TBR at 2-h was 21% (SD = 0.31).

CONCLUSIONS

[¹⁸F]F-Florastamin is a promising new radioligand for PSMA-targeted PET with suitable lesion detectability and high TBR at both time points.

Comparison of 18 F-PSMA-1007 PET/CT With 68 Ga-PSMA-11 PET/CT for Initial Staging in Intermediate- and High-Risk Prostate Cancer

PURPOSE

This study aimed to compare 18 F-PSMA-1007 PET/CT with 68 Ga-PSMA-11 PET/CT for initial staging in intermediate- and high-risk prostate cancer (PCa) patients.

METHODS

Forty treatment-naive, biopsy-proven, intermediate- or high-risk PCa patients were prospectively recruited. Each patient underwent PET/CT with 68 Ga-PSMA-11 and 18 F-PSMA-1007 (within 2 weeks). Assessment of both set of images included delineating number and characteristics of lesions, measurement of tracer uptake (SUV max ), miPSMA scoring, and PET-based stage categorization.

RESULTS

Intraprostatic lesions were detected in all patients by both tracers with concordant PET-based T stage. Median SUV max of the dominant PSMA-positive prostatic lesions was not significantly different with 18 F-PSMA-1007 and 68 Ga-PSMA-11 (19.9 vs 19.4, P = 0.127, n = 40). Prostatic miPSMA scores were similar in 31/40 (77.5%) patients with both tracers (weighted κ = 0.71). In 23/40 (57.5%) patients, regional lymph nodes (n = 171) were detected by both tracers. Few additional PET-positive regional lymph nodes (n = 3) were exclusively detected by 18 F-PSMA in 2 patients without altering PET-based N stage. Extraregional lymph nodes (n = 123 in 17/40 patients) and visceral metastatic lesions (n = 18 in 3/40 patients) were detected concordantly by both tracers. PET-positive marrow based and skeletal metastases (n = 71) were detected in 14/40 (35%) patients by both tracers. Few additional marrow and skeletal lesions (n = 7) were exclusively detected on 18 F-PSMA-1007 in 5/14 patients, potentially upstaging PET-based M stage in 2/5 patients. Both radiotracers showed excellent interreader agreement for region-wise detection of lesions.

CONCLUSIONS

Our results suggest that 18 F-PSMA-1007 PET/CT is comparable to 68 Ga-PSMA-11 PET/CT in detecting primary and metastatic lesions of PCa.

Preclinical Evaluation of a Companion Diagnostic Radiopharmaceutical, [18F]PSMA-1007, in a Subcutaneous Prostate Cancer Xenograft Mouse Model

Several radiolabeled prostate-specific membrane antigen (PSMA)-targeted agents have been developed for detecting prostate cancer, using positron emission tomography imaging and targeted radionuclide therapy. Among them, [¹⁸F]PSMA-1007 has several advantages, including a comparatively long half-life, delayed renal excretion, and compatible structure with α-/β-particle emitter-labeled therapeutics. This study aimed to characterize the preclinical pharmacokinetics and internal radiation dosimetry of [¹⁸F]PSMA-1007, as well as its repeatability and specificity for target binding using prostate tumor-bearing mice. In PSMA-positive tumor-bearing mice, the kidney showed the greatest accumulation of [¹⁸F]PSMA-1007. The distribution in the tumor attained its peak concentration of 2.8%ID/g at 112 min after intravenous injection. The absorbed doses in the tumor and salivary glands were 0.079 ± 0.010 Gy/MBq and 0.036 ± 0.006 Gy/MBq, respectively. The variance of the net influx (K_i) of [¹⁸F]PSMA-1007 to the tumor was minimal between scans performed in the same animals (within-subject coefficient of variation = 7.57%). [¹⁸F]PSMA-1007 uptake in the tumor was specifically decreased by 32% in K_i after treatment with a PSMA inhibitor 2-(phosphonomethyl)-pentanedioic acid (2-PMPA). In the present study, we investigated the in vivo preclinical characteristics of [¹⁸F]PSMA-1007. Our data from [¹⁸F]PSMA-1007 PET/computed tomography (CT) studies in a subcutaneous prostate cancer xenograft mouse model supports clinical therapeutic strategies that use paired therapeutic radiopharmaceuticals (such as [¹⁷⁷Lu]Lu-PSMA-617), especially strategies with a quantitative radiation dose estimate for target lesions while minimizing radiation-induced toxicity to off-target tissues.

Recurrent Prostate Cancer Diagnostics with 18F-PSMA-1007 PET/CT: A Systematic Review of the Current State

BACKGROUND

Early diagnosis of recurrent prostate cancer is a cornerstone for further adequate therapy planning. Therefore, clinical practice and research still focuses on diagnostic tools that can detect prostate cancer in early recurrence when it is undetectable in conventional diagnostic imaging. ¹⁸F-PSMA-1007 PET/CT is a novel method to evaluate patients with biochemical recurrent PCa. The aim of this review was to evaluate the role of ¹⁸F-PSMA-1007 PET/CT in prostate cancer local recurrence, lymph node metastases and bone metastases detection.

METHODS

Original studies, reviews and five meta-analyses were included in this article. A total of 70 studies were retrieved, 31 were included in the study.

RESULTS

All patients described in the studies underwent ¹⁸F-PSMA-1007 PET/CT. The administered ¹⁸F-PSMA-1007 individual dose ranged from 159 ± 31 MBq to 363.93 ± 69.40 MBq. Results showed that ¹⁸F-PSMA-1007 PET/CT demonstrates a good detection rate in recurrent prostate cancer.

CONCLUSIONS

¹⁸F-PSMA-1007 PET/CT appears to achieve reliable performance in detecting recurrent prostate cancer. The high detection rate of ¹⁸F-PSMA-1007 PET/CT in recurrent prostate cancer was confirmed, especially in local recurrence and small lymph nodes with non-specific characteristics on conventional diagnostic imaging methods. However, several authors emphasize some limitations for this tracer-for example, non-specific uptake in bone lesions that can mimic bone metastases.

Preclinical evaluation and first in human study of Al18F radiolabeled ODAP-urea-based PSMA targeting ligand for PET imaging of prostate cancer

PURPOSE

This study aimed to introduce a novel [18F]AlF-labeled ODAP-Urea-based Prostate-specific membrane antigen (PSMA) probe, named [18F]AlF-PSMA-137, which was derived from the successful modification of glutamate-like functional group. The preclinically physical and biological characteristics of the probe were analyzed. Polit clinical PET/CT translation was performed to analyze its feasibility in clinical diagnosis of prostate cancer.

METHODS

[18F]AlF-PSMA-137 was maturely labeled with the [18F]AlF2+ labeling technique. It was analyzed by radio-HPLC for radiochemical purity and stability analysis in vitro and in vivo. The PSMA specificity was investigated in PSMA-positive (LNCaP) and PSMA-negative (PC3) cells, and the binding affinity was evaluated in LNCaP cells. Micro-PET/CT imaging was performed in mice bearing LNCaP or PC3 tumors. Thirteen patients with newly diagnosed prostate cancer were included for [18F]AlF-PSMA-137 PET/CT imaging. Physiologic biodistribution and tumor burden were semi-quantitatively evaluated and the radiation dosimetry of [18F]AlF-PSMA-137 was estimated.

RESULTS

The radiochemical yield of [18F]AlF-PSMA-137 was 54.2 ± 10.7% (n = 16) with the radiochemical purity over 99% and the specific activity of 26.36 ± 7.33 GBq/μmol. The binding affinity to PSMA was 2.11 ± 0.63 nM. [18F]AlF-PSMA-137 showed high cell/tumor uptake which can be specifically blocked by PSMA inhibitor. According to the biodistribution in patients, [18F]AlF-PSMA-137 was mainly accumulated in kidneys, lacrimal glands, parotid glands, submandibular glands and liver which was similar to the extensive Glu-Ureas based probes. A total of 81 lesions were detected in PET/CT imaging and over 91% of lesions increased between 1 h p.i. (SUVmean: 10.98 ± 18.12) and 2 h p.i. (SUVmean: 14.25 ± 21.28) (p < 0.001). Additionally, the probe showed intensive accumulation in lesions which provided excellent imaging contrast with the high tumor-to-muscle ratio of 15.57 ± 27.21 at 1 h p.i. and 25.42 ± 36.60 at 2 h p.i. (p < 0.001), respectively. The effective dose of [18F]AlF-PSMA-137 was estimated as 0.0119 ± 0.0009 mSv/MBq.

CONCLUSION

An ODAP-Urea-based PSMA probe [18F]AlF-PSMA-137 was successfully prepared with high specificity and binding affinity to PSMA. Micro-PET/CT imaging study demonstrated its feasibility for prostate cancer imaging. Pilot clinical study showed its potential for delay-imaging and prostate cancer detection.

Preclinical comparative study of [18F]AlF-PSMA-11 and [18F]PSMA-1007 in varying PSMA expressing tumors

A wide variety of ¹⁸F-labeled PSMA-targeting PET radiotracers have been developed, including [¹⁸F]AlF-PSMA-11. As there is only limited data on the comparison with other ¹⁸F-labeled PSMA PET tracers, a comparative preclinical study between [¹⁸F]AlF-PSMA-11 and [¹⁸F]PSMA-1007 was conducted. Mice with varying PSMA expressing tumors (C4-2, 22Rv1 and PC-3, each n = 5) underwent two PET/CT scans with both [¹⁸F]AlF-PSMA-11 and [¹⁸F]PSMA-1007. Ten additional mice bearing C4-2 xenografts were subjected to ex vivo biodistribution with either [¹⁸F]AlF-PSMA-11 (n = 5) or [¹⁸F]PSMA-1007 (n = 5). Absolute SUV_mean and SUV_max values were significantly higher for [¹⁸F]PSMA-1007 scans in both C4-2 tumors (p < 0.01) and 22Rv1 tumors (p < 0.01). In C4-2 xenograft bearing mice, the tumor-to-organ ratios did not significantly differ between [¹⁸F]AlF-PSMA-11 and [¹⁸F]PSMA-1007 for liver, muscle, blood and salivary glands (p > 0.05). However, in 22Rv1 xenograft bearing mice, all tumor-to-organ ratios were higher for [¹⁸F]AlF-PSMA-11 (p < 0.01). In healthy organs, [¹⁸F]PSMA-1007 uptake was higher in the liver, gallbladder, small intestines and glands. Biodistribution data confirmed the increased uptake in the heart, small intestines and liver with [¹⁸F]PSMA-1007. Absolute tumor uptake was higher with [¹⁸F]PSMA-1007 in all tumors. Tumor-to-organ ratios did not differ significantly in high PSMA expressing tumors, but were higher for [¹⁸F]AlF-PSMA-11 in low PSMA expressing tumors. Furthermore, [¹⁸F]PSMA-1007 showed higher uptake in healthy organs.

Urothelial Carcinoma and Prostate-specific Membrane Antigen: Cellular, Imaging, and Prognostic Implications

CONTEXT

Staging, restaging, and surveillance of urothelial carcinoma (UC) is challenging due to suboptimal accuracy of standard of care imaging modalities. Prostate-specific membrane antigen (PSMA) imaging may serve to improve characterisation of UC.

OBJECTIVE

To appraise available literature regarding cellular, imaging, and prognostic implications of PSMA for UC.

EVIDENCE ACQUISITION

A systematic review was performed considering all available literature (including conference abstracts) published from 1990 to 2020 and reported according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines following registration in PROSPERO (CRD42020186744). All relevant texts relating to immunohistochemical analysis and PSMA-based imaging in UC were included and collated. Additionally, FOLH1 (gene encoding PSMA) expression according to The Cancer Genome Atlas (TCGA) database was analysed as well as according to consensus and TCGA molecular classification subtypes and subsequently compared with clinical outcomes.

EVIDENCE SYNTHESIS

PSMA expression across UC tumour tissue was heterogeneous (0-100%) but appeared to decrease with increased grade and stage. The TCGA analysis demonstrated loss of FOLH1 expression with increasing T stage (p = 0.0180) and N stage (p = 0.0269), and reduced FOLH1 expression was associated with worse disease-free survival. PSMA expression in UC neovasculature was variable but mostly increased (44-100%). Eleven reports of PSMA-based imaging for UC were identified, reporting on 18 patients. PSMA positron emission tomography (PET) imaging was positive in 17 out of 18 patients. The included literature review data were limited by mostly low-quality, retrospective studies.

CONCLUSIONS

Tissue PSMA, or FOLH1 expression, may inversely be associated with pathological and survival outcomes in localised UC. PSMA PET imaging may improve detection of metastatic disease and response to systemic therapy due to PSMA expression in neovasculature. Available evidence is limited; thus, larger, prospective studies are required to confirm early results and define populations that benefit most.

PATIENT SUMMARY

In this systematic review, we assess the potential role of prostate-specific membrane antigen in urothelial cancer. We found that its utility is in expression of blood vessels surrounding metastasis. We conclude that it may be beneficial in detecting metastasis and response to systemic therapies.

Clinical Applications of PSMA PET Examination in Patients with Prostate Cancer

Simple Summary

The prostate specific membrane antigens, abbreviated as PSMAs, are type II membrane proteins that are highly ex-pressed on the surface of malignant prostate tissue in prostate cancer (PCa), particularly in aggressive, andro-gen-deprived, metastatic, and hormone-refractory PCa. Today, radionuclides that bind to these PSMA peptides are widely available for diagnostic and therapeutic purposes to specifically image and target prostate tumor cells at molec-ular level. In this descriptive review, we aimed to emphasize the usefulness of PSMA positron emission tomography (PET) examination in the management of patients with various stages of PCa. In addition, we outlined the main pitfalls and limitations of this scan to avoid misinterpretation of the results and to improve the decision making process in rela-tion to the patient’s further treatment. We concluded that PSMA PET examination in primary PCa patients has an es-sential role in the high-risk group. It is the new imaging standard in patients with in biochemical recurrence PCa and plays an important role in treatment decision. Furthermore, PSMA PET scan is a gold standard for the evaluation of PSMA targeted therapies in patients having progress of the disease. Future prospective studies, particularly on the im-pact of PSMA PET on therapy stratification, may further strengthen the role of PSMA in the treatment of PCa patients.

Abstract

With the progressive aging of the population in industrially developed countries, as well as advances in diagnostic and biopsy techniques and improvements in patient awareness, the incidence of prostate cancer (PCa) is continuously increasing worldwide. Therefore, PCa is currently considered as the second leading cause of tumor-related death. Early detection of the tumor and its metastasis is essential, as the rate of disease recurrence is high and occurs in 27% to 53% of all patients who underwent curative therapy with radical prostatectomy or local radiotherapy. In this regard, the prostate specific membrane antigens, abbreviated as PSMAs, are type II membrane proteins that are highly expressed on the surface of malignant prostate tissue in PCa, particularly in aggressive, androgen-deprived, metastatic, and hormone-refractory PCa, and they are inversely associated with the androgen level. Up to 95% of adenocarcinomas of the prostate express PSMA receptors on their surface. Today, radionuclides that bind to these PSMA peptides are widely accepted for diagnostic and therapeutic purposes to specifically image and target prostate tumor cells at the molecular level, a process referred to as targeted theranostics. Numerous studies have demonstrated that the integration of these peptides into diagnostic and therapeutic procedures plays a critical role in the primary staging and treatment decisions of especially high-risk PCa, expands therapeutic options for patients with advanced stage of prostate tumor, and prolongs patients’ survival rate. In this review article, we intend to briefly spotlight the latest clinical utilization of the PSMA-targeted radioligand PET imaging modality in patients with different stages of PCa. Furthermore, limitations and pitfalls of this diagnostic technique are presented.

A randomised, prospective and head-to-head comparison of [68Ga]Ga-PSMA-11 and [18F]PSMA-1007 for the detection of recurrent prostate cancer in PSMA-ligand PET/CT-Protocol design and rationale

Background

A number of radiopharmaceuticals are available for the detection of recurrent prostate cancer (rPC), but few comparative imaging trials have been performed comparing them. In particular, there are no prospective head-to-head comparisons of the recently introduced [¹⁸F]PSMA-1007 to the existing standard of care [⁶⁸Ga]Ga-PSMA-11. The purpose of this trial is to establish the non-inferiority of the new radiopharmaceutical in terms of the rate of PET-positive findings and to obtain an intra-individual comparison of accuracy and radiopharmaceutical kinetics.

Methods

In this cross-over trial we will randomise 100 individuals to receive either first a standard-of-care PET/CT using [⁶⁸Ga]Ga-PSMA-11 followed by an additional [¹⁸F]PSMA-1007 PET/CT within 2 weeks, or vice-versa. Inclusion criteria include patients 18 years and older with biochemical recurrence of prostate cancer following radical prostatectomy, defined as two consecutive prostate specific antigen (PSA) levels > 0.2 ng/ml. Detection rate at the patient-based level is the primary end-point. Each scan will be interpreted by a panel of six independent and masked readers (three for [⁶⁸Ga]Ga-PSMA-11 and three for [¹⁸F]PSMA-1007) which consensus majority in cases of discrepancy. To confirm the PET-positivity rate at a patient based level, follow up at 6 months following the first scan will be performed to a composite standard of truth. Secondary endpoints shall include an intra-individual comparison of radiopharmaceutical-kinetics, per-region detection rate and positive predictive value.

Discussion

This is the first randomised prospective comparative imaging trial to compare the established [⁶⁸Ga]Ga-PSMA-11 with [¹⁸F]PSMA-1007 and will determine whether the new radiopharmaceutical is non-inferior to the established standard-of-care in terms of patient-level detection rate.

Clinical trial registration

Registered with and approved by the regional ethics authority #2020–02903 (submitted 09.12.2020, approval 16.12.2021) and the regulatory authority SwissMedic 2020DR2103. Registered with ClinicalTrials.gov Identifier NCT05079828 and additionally in a national language in the Swiss National Clinical Trials Portal (SNCTP).

Detection rate of fluorine-18 prostate-specific membrane antigen-1007 PET/CT for prostate cancer in primary staging and biochemical recurrence with different serum PSA levels: A systematic review and meta-analysis

Background

We performed a systematic review and meta-analysis to evaluate the detection rate (DR) of fluoro-prostate-specific membrane antigen (¹⁸F-PSMA-1007) PET/CT in patients with different serum prostate-specific antigen (PSA) levels in the setting of primary staging of prostate cancer (PCa) or biochemically recurring PCa.

Methods

A comprehensive electronic literature search of the PubMed, Embase, and Cochrane Library databases was conducted in accordance with the PRISMA statement. This study was registered in the PROSPERO database (registration number: CRD42022331595). We calculated the DR of ¹⁸F-PSMA-1007 PET/CT in PCa.

Results

The final analysis included 15 studies that described 1,022 patients and 2,034 lesions with ¹⁸F-PSMA-1007 PET/CT in PCa. The DR of ¹⁸F-PSMA-1007 PET/CT in patients with PCa in primary staging ranged from 90% to 100%, with a pooled estimate of 94% (95% CI: 92%–96%). The DR of ¹⁸F-PSMA-1007 PET/CT in patients with PCa in BCR ranged from 47% to 100%, with a pooled estimate of 86% (95% CI: 76%–95%). The DRs of PSA levels >2.0, 1.1–2.0, 0.51–1.0, and ≤0.5 ng/ml detected by ¹⁸F-PSMA-1007 PET/CT in a patient-based analysis were 97% (95% CI: 93%–99%), 95% (95% CI: 88%–99%), 79% (95% CI: 68%–88%), and 68% (95% CI: 58%–78%), respectively.

Conclusion

This meta-analysis concluded that ¹⁸F-PSMA-1007 PET/CT had a high application value for prostate cancer, including primary tumors and biochemical recurrence. The DR of ¹⁸F-PSMA-1007 PET/CT was slightly higher in primary prostate tumors than in biochemical recurrence.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022331595.

The future of PSMA PET and WB MRI as next-generation imaging tools in prostate cancer

Radiolabelled prostate-specific membrane antigen (PSMA)-based PET-CT has been shown in numerous studies to be superior to conventional imaging in the detection of nodal or distant metastatic lesions. ⁶⁸Ga-PSMA PET-CT is now recommended by many guidelines for the detection of biochemically relapsed disease after radical local therapy. PSMA radioligands can also function as radiotheranostics, and Lu-PSMA has been shown to be a potential new line of treatment for metastatic castration-resistant prostate cancer. Whole-body (WB) MRI has been shown to have a high diagnostic performance in the detection and monitoring of metastatic bone disease. Prospective, randomized, multicentre studies comparing ⁶⁸Ga-PSMA PET-CT and WB MRI for pelvic nodal and metastatic disease detection are yet to be performed. Challenges for interpretation of PSMA include tracer trapping in non-target tissues and also urinary excretion of tracers, which confounds image interpretation at the vesicoureteral junction. Additionally, studies have shown how long-term androgen deprivation therapy (ADT) affects PSMA expression and could, therefore, reduce tracer uptake and visibility of PSMA⁺ lesions. Furthermore, ADT of short duration might increase PSMA expression, leading to the PSMA flare phenomenon, which makes the accurate monitoring of treatment response to ADT with PSMA PET challenging. Scan duration, detection of incidentalomas and presence of metallic implants are some of the major challenges with WB MRI. Emerging data support the wider adoption of PSMA PET and WB MRI for diagnosis, staging, disease burden evaluation and response monitoring, although their relative roles in the standard-of-care management of patients are yet to be fully defined.

Diagnostic accuracy of [18F]PSMA-1007 PET/CT in biochemical recurrence of prostate cancer

AIM

Despite increasing use for the detection of biochemically recurrent prostate cancer (rPC), the diagnostic accuracy of positron emission tomography/computed tomography (PET/CT) with [18F]PSMA-1007 remains only partially investigated. The aim of this study was to determine the sensitivity (SE), specificity (SP), positive predictive value (PPV), and negative predictive value (NPV) for PC-local recurrence and metastases on a per region basis.

MATERIALS AND METHODS

One hundred seventy-seven consecutive patients undergoing [18F]PSMA-1007 PET/CT for rPC were retrospectively analysed. Six body regions were defined: prostate fossa, pelvic lymph nodes (LN), retroperitoneal LN, supradiaphragmatic LN, bones, and soft tissue. A region was counted positive if at least one PSMA-positive lesion suspicious for PC was observed. Confirmation of a true-positive PSMA-avid lesion was defined as positive by histopathology, fall in serum prostate-specific antigen (PSA) (> 50%) after targeted therapy or confirmatory further CT, MRI, PET/CT, or bone scan imaging. Regions where additional imaging was able to confirm the absence of suspicious PC lesions or regions outside exclusively targeted RT with serum PSA decline (> 50%) were counted as true-negative regions. SE, SP, PPV, and NPV were calculated for all six regions.

RESULTS

The overall PET-positivity rate was 91%. Conclusive follow-up for affirmation or refutation of a PSMA-positive lesion was available for 81/152 patients on a per region basis. In this subgroup, overall sensitivity, specificity, PPV, and NPV were 95% (CI: 0.90-0.98), 89% (CI: 0.83-0.93), 86% (0.80-0.90), and 96% (CI: 0.92-0.98), respectively. On a per region basis, PPV was 97% (CI: 0.83-0.99) for local recurrence, 93% (CI: 0.78-0.98) for pelvic LN, 87% (CI: 0.62-0.96) for retroperitoneal LN, 82% (CI: 0.52-0.95) for supradiaphragmatic LN, and 79% (0.65-0.89) for bone lesions. The number of solid organ metastases (n = 6) was too small for an accurate statistical analysis.

CONCLUSION

The known high PET-positivity rate of [18F]PSMA-1007 PET/CT in rPC was confirmed, with corresponding high (> 90%) sensitivity and NPV on a per region basis. However, overall PPV was limited (86%), particularly for bone lesions (79%), which are a potential diagnostic weaknesses when using this tracer.

Prospective intraindividual comparison of 18F-PSMA-7Q and 18F-DCFPyL PET/CT in patients with newly diagnosed prostate cancer

OBJECTIVE

Fluorine 18 (18F)-2-(3-{1-Carboxy-5-[(6-[(18)F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (DCFPyL) is an early 18F-labeled prostate-specific membrane antigen (PSMA) targeted PET tracer that has shown promise in the diagnostic workup of prostate cancer and was recently approved by the US Food and Drug Administration. 18F-PSMA-7Q is a novel 18F-labeled PSMA-ligand PET tracer designed and synthesized by our team. This study compared the tracer-specific positron emission tomography/computed tomography (PET/CT) characteristics of 18F-PSMA-7Q with those of 18F-DCFPyL in patients with newly diagnosed prostate cancer.

METHODS

Ten patients received similar doses of 18F-DCFPyL and 18F-PSMA-7Q 48 h apart and were imaged 1 h after injection on the same PET/CT scanner. Normal-organ biodistribution and tumor uptake were quantified using maximum and mean standardized uptake values (SUVmax and SUVmean), and all lesions were assigned a molecular imaging PSMA (miPSMA) score based on Prostate Cancer Molecular Imaging Standardized Evaluation criteria.

RESULTS

Seventeen lesions were detected in the 10 patients by both 18F-DCFPyL and 18F-PSMA-7Q. No statistically significant difference was observed when comparing the SUVmax and SUVmean of 18F-DCFPyL and 18F-PSMA-7Q in the lesions and parotid gland. The κ value for the miPSMA scores of the lesions between the two tracers was 0.907, indicating excellent agreement.

CONCLUSION

18F-PSMA-7Q can be used in clinical research as reliably as 18F-DCFPyL. The limited urinary excretion of 18F-PSMA-7Q may represent a potential advantage over 18F-DCFPyL for detection of lesions in the pelvis, which need to be verified by further studies.

PSMA theragnostics for metastatic castration resistant prostate cancer

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PSMA targeted theragnostic agents have shown tremendous potential in detecting and treating metastatic prostate cancer.

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The PSMA small molecular inhibitor-based imaging agents achieve extraordinary tumor to background ratios and the PSMA small molecule therapeutic agents have shown impressive therapeutic index in mCRPC.

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The development and optimization of PSMA theragnostic agents provides invaluable information that may help guide development of future theragnostics for other solid tumors.

There has been tremendous growth in the development of theragnostics for personalized cancer diagnosis and treatment over the past two decades. In prostate cancer, the new generation of prostate specific membrane antigen (PSMA) small molecular inhibitor-based imaging agents achieve extraordinary tumor to background ratios and allow their therapeutic counterparts to deliver effective tumor doses while minimizing normal tissue toxicity. The PSMA targeted small molecule positron emission tomography (PET) agents ¹⁸F-DCFPyL (2-(3-{1-carboxy-5-((6-(18)F-fluoro-pyridine-3-carbonyl)-amino)-pentyl}-ureido)-pentanedioic acid) and Gallium-68 (⁶⁸Ga)-PSMA-11 have been approved by the United States Food and Drug Administration (FDA) for newly diagnosed high risk prostate cancer patients and for patients with biochemical recurrence. More recently, the Phase III VISION trial showed that Lutetium-177 (¹⁷⁷Lu)-PSMA-617 treatment increases progression-free survival and overall survival in patients with heavily pre-treated advanced PSMA-positive metastatic castration-resistant prostate cancer (mCRPC). Here, we review the PSMA targeted theragnostic pairs under clinical investigation for detection and treatment of metastatic prostate cancer.

Imaging Biomarkers in Prostate Stereotactic Body Radiotherapy: A Review and Clinical Trial Protocol

Advances in imaging have changed prostate radiotherapy through improved biochemical control from focal boost and improved detection of recurrence. These advances are reviewed in the context of prostate stereotactic body radiation therapy (SBRT) and the ARGOS/CLIMBER trial protocol. ARGOS/CLIMBER will evaluate 1) the safety and feasibility of SBRT with focal boost guided by multiparametric MRI (mpMRI) and ¹⁸F-PSMA-1007 PET and 2) imaging and laboratory biomarkers for response to SBRT. To date, response to prostate SBRT is most commonly evaluated using the Phoenix Criteria for biochemical failure. The drawbacks of this approach include lack of lesion identification, a high false-positive rate, and delay in identifying treatment failure. Patients in ARGOS/CLIMBER will receive dynamic ¹⁸F-PSMA-1007 PET and mpMRI prior to SBRT for treatment planning and at 6 and 24 months after SBRT to assess response. Imaging findings will be correlated with prostate-specific antigen (PSA) and biopsy results, with the goal of early, non-invasive, and accurate identification of treatment failure.

Head-to-Head Comparison of 68Ga-PSMA-11 PET/CT and 99mTc-MDP Bone Scintigraphy for the Detection of Bone Metastases in Patients With Prostate Cancer: A Meta-Analysis

Background: Bone scintigraphy (BS) using 99mTc-MDP remains the recommended imaging modality for the detection of bone metastases in patients with prostate cancer (PCa). However, PET/CT using prostate-specific membrane antigen (PSMA) ligands is increasingly recognized for evaluating disease extent in patients with PCa, including as a possible standalone test in high-risk patients. Objective: To compare the diagnostic performance of 68Ga-PSMA-PET/CT and 99mTc-MDP BS for the detection of bone metastases in patients with PCa. Evidence Acquisition: PubMed, Embase, and Cochrane Library databases were searched through October 2021 for studies reporting a head-to-head comparison of 68Ga-PSMA-PET/CT and 99mTc-MDP BS for the detection of bone metastases in patients with PCa. Only studies with a well-defined reference standard (including various combinations of imaging and/or clinical follow-up) were included. Pooled diagnostic performance was calculated using bivariate random-effects model, and AUC was derived for each test from hierarchical summary ROC analysis. The two tests' complementary roles in identifying bone metastases in patients in whom the other test was negative were summarized. Evidence Synthesis: Six studies with 546 patients were included. The pooled sensitivity and specificity were 98% (95% CI: 94%-99%) and 97% (95% CI: 91%-99%) for 68Ga-PSMA-11 PET/CT versus 83% (95% CI: 69%-91%) and 68% (95% CI: 41%-87%) for 99mTc-MDP BS. The AUC was 0.99 (95% CI: 0.96-1.00) for 68Ga-PSMA-11 PET/CT and 0.85 (95% CI: 0.81-0.87) for 99mTc-MDP BS. In 408 patients from five included studies, 68Ga-PSMA-11 PET/CT correctly identified bone metastases in 43 (22.3%) of 193 patients with negative 99mTc-MDP BS results, whereas 99mTc-MDP BS correctly identified bone metastases in 4 (1.9%) of 210 patients with negative 68Ga-PSMA-11 PET/CT results. Conclusion: On a per-patient basis, 68Ga-PSMA-11 PET/CT has superior diagnostic performance than 99mTc-MDP BS for the detection of prostate cancer bone metastases. Furthermore, 99mTc-MDP BS offers limited additional information in patients with negative 68Ga-PSMA-11 PET/CT results. Clinical impact: According to current evidence, 99mTc-MDP BS is highly unlikely to be additive to 68Ga-PSMA-11 PET/CT in identifying bone metastases in patients with prostate cancer.

The Diagnostic Performance of 18F-PSMA-1007 PET/CT in Prostate Cancer Patients with Early Recurrence after Definitive Therapy with a PSA <10 ng/ml

AIM

The prostate bed is one of the common sites of early recurrence of prostate cancer. The currently used PSMA ligands (⁶⁸Ga-PSMA-11 and ^99mTc-PSMA) undergo early urinary clearance resulting in interfering physiological activity within and surrounding the prostate. This can result in sites of cancer recurrence being obscured. ¹⁸F-PSMA-1007 has an advantage of delayed urinary clearance thus the prostate region is reviewed without any interfering physiological activity. The aim of this study was to determine the diagnostic performance of ¹⁸F-PSMA-1007 PET/CT in patients with early biochemical recurrence after definitive therapy.

METHODS

Forty-six Prostate cancer (mean age 66.7±7.5, range 48-87 years) presenting with biochemical recurrence (median PSA 1.6ng/ml, range 0.1-10.0) underwent non-contrast-enhanced ¹⁸F-PSMA-1007 PET/CT. PET/CT findings were evaluated qualitatively and semiquantitatively (SUVmax) and compared to the results of histology, Gleason grade, and conventional imaging.

RESULTS

Twenty-four of the 46 (52.2%) patients demonstrated a site of recurrence on ¹⁸F-PSMA-1007 PET/CT. Oligometastatic disease was detected in 15 (32.6%) of these patients. Of these 10 (37.5%) demonstrated intra-prostatic recurrence, lymph node disease was noted in 11 (45.8%) whilst two patients demonstrated skeletal metastases. The detection rates for PSA levels 0-<0.5, 0.5-<1, 1-2, >2 were 31.3%, 33.3%, 55.6% and 72.2% respectively. 7 (29.2%) of the positive patients had been described as negative or equivocal on conventional imaging. An optimal PSA cut-off level of 1.3ng/ml was found.

CONCLUSION

¹⁸F-PSMA-1007 demonstrated good diagnostic performance detecting sites of recurrence. Its ability to detect sites of recurrence in the setting of early biochemical recurrence will have a significant impact on patient management.

Comparison of [18F]PSMA-1007 with [68Ga]Ga-PSMA-11 PET/CT in Restaging of Prostate Cancer Patients with PSA Relapse

This study aimed to compare the diagnostic performance of [18F]PSMA-1007 positron emission tomography/computed tomography (PET/CT) (18F-PSMA) and [68Ga]Ga-PSMA-11 PET/CT (68Ga-PSMA) by identifying prostate-specific antigen (PSA) threshold levels for optimal detecting recurrent prostate cancer (PC) and to compare both methods. Retrospectively, the study included 264 patients. The performances of 18F-PSMA and 68Ga-PSMA in relation to the pre-scan PSA were assessed by receiver operating characteristic (ROC) curve. 18F-PSMA showed PC-lesions in 87.5% (112/128 patients), while 68Ga-PSMA identified them in 88.9% (121/136). For 18F-PSMA biochemical recurrent (BCR) patients treated with radical prostatectomy (78/128, patient group: F-RP), a PSA of 1.08 ng/mL was found to be the optimal cut-off level for predicting positive and negative scans (AUC = 0.821; 95%, CI: 0.710−0.932), while for prostatectomized 68Ga-PSMA BCR-patients (89/136, patient group: Ga-RP), the cut-off was 1.84 ng/mL (AUC = 0.588; 95%, CI: 0.410−0.766). In patients with PSA < 1.08 ng/mL (F-RP) 76.3% and <1.84 ng/mL (Ga-RP) 78.6% scans were positive, whereas patients with PSA ≥ 1.08 ng/mL (F-RP) or 1.84 ng/mL (Ga-RP) had positive scan results in 100% and 91.5% (p < 0.001/p = 0.085). The identified PSA thresholds for PSMA-mappable PC lesions in BCR-patients (RP) showed a better separation for 18F-PSMA with regard to the distinguishing of positive and negative PC-lesions compared to 68Ga-PSMA. However, the two PSMA PET/CT tracers gave similar overall findings.

Diagnostic value of integrated 18F-PSMA-1007 PET/MRI Compared with that of Biparametric MRI for the detection of Prostate Cancer

Objective

Materials and methods

Results

Conclusion

Standardised Uptake Values as Determined on PSMA PET/CT is associated with Oncological Outcomes in Prostate Cancer Patients

Objectives

To investigate the association between intraprostatic, intratumoral maximum standardised uptake values (SUV_max) on prostate‐specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) in patients with prostate cancer (PCa) prior to robot‐assisted radical prostatectomy (RARP) and pathology outcomes, including pathological International Society of Urological Pathology score (pISUP) and lymph node (LN) status (pN0/pN1).

Patients and Methods

A bi‐centric, secondary analysis of two previous, prospective cohort studies was performed in 318 patients with biopsy confirmed PCa and who were scheduled for RARP. Before surgery, patients received a PSMA PET/CT with either ⁶⁸Ga‐PSMA‐11 (59% of the patients) or ¹⁸F‐PSMA (DCFPyL; 41%) as radiotracer. PET/CT images were analysed both visually and semi‐quantitatively by measuring the SUV_max of the most intense suspect lesion in the prostate. The association between the SUV_max of the primary tumour and pre‐ and postoperative variables was analysed.

Results

The SUV_max was associated with clinical and biopsy preoperative variables, as well as with pISUP score and pathological tumour stage. Patients with a pISUP of ≤2 showed significantly lower SUV_max compared to patients with a pISUP of >2 for both tracers (SUV_max¹⁸F‐PSMA: median 5.1 vs 9.6, P = 0.002; SUV_max⁶⁸Ga‐PSMA‐11: 6.6 vs 8.6, P = 0.003). Moreover, patients with pN1 had significantly higher median SUV_max than those with pN0/pNx for both tracers (SUV_max¹⁸F‐PSMA: 7.9 vs 12.3, P = 0.04; SUV_max⁶⁸Ga‐PSMA‐11: 7.6 vs 12.0, P < 0.001). On multivariable logistic regression analysis, the intraprostatic SUV_max was an independent predictor of pN1 for both ⁶⁸Ga‐PSMA‐11 (per doubling: odds ratio [OR] 1.96, 95% confidence interval [CI] 1.27–3.01)) and ¹⁸F‐PSMA (per doubling: OR 1.79, 95% CI 1.06–3.03).

Conclusion

Intraprostatic, intratumoral PSMA intensity on PET/CT, as semi‐quantitatively expressed by SUV_max, may be a valuable innovative biomarker in patients with localised PCa, as it is highly associated with known conventional prognostic factors, such as pISUP and LN status.

Identification of the Optimal Cut-Off Value of PSA for Assessing Severity of Disease in [68Ga]Ga-PSMA-11 PET/CT Study in Prostate Cancer Patients after Radical Prostatectomy

Objective: The objective of this study was to identify the optimal cut-off value of prostate specific antigen (PSA) to assess the extent of the disease in [68Ga]Ga-PSMA-11 PET/CT study in patients after radical prostatectomy. Materials and Methods: Retrospective analysis was performed on a group of 215 patients who underwent a [68Ga]Ga-PSMA-11 PET/CT examination because of suspected recurrence after radical prostatectomy. Patients were divided into four groups: 1, no active lesions suggesting recurrence (n = 92); 2, suspected isolated local recurrence (n = 19); 3, oligometastatic disease (n = 82); and 4, polymetastatic disease (n = 22). Results: In group 1, the mean PSA level was 0.962 ng/mL (median: 0.376; min: 0.004; max: 25 ng/mL); in group 2, it was 4.970 ng/mL (median 1.320; min: 0.003; max: 40.350 ng/mL); in group 3, it was 2.802 ng/mL (median: 1.270; min: 0.020; max: 59.670 ng/mL); and in group 4, it was 4.997 ng/mL (median: 3.795; min: 0.007; max 21.110 ng/mL). Statistically significant differences were shown in PSA levels when comparing groups 1 and 2 (p = 0.0025) and groups 3 and 4 (p = 0.0474). The PSA cut-off point for discriminating groups 1 and 2 was 0.831 (sensitivity: 0.684; specificity: 0.772; area under the curve (AUC): 0.775), and for groups 3 and 4, it was 2.51 (sensitivity: 0.682; specificity: 0.780; AUC: 0.720). Conclusions: Our preliminary data suggested that the PSA level has an essential influence on determining the extent of disease in a [68Ga]Ga-PSMA-11 PET/CT study in patients after radical prostatectomy. Identification of the optimal cut-off values for the oligo- and polymetastatic diseases might be helpful in stratifying these patients.

Pretherapeutic estimated glomerular filtration rate predicts development of chronic kidney disease in patients receiving PSMA-targeted radioligand therapy

BACKGROUND

Prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) may be associated with renal toxicity. We aimed to identify predictive parameters for the development of chronic kidney disease (CKD) in patients with metastatic castration resistant prostate cancer (mCRPC) undergoing RLT.

METHODS

In 46 mCRPC patients scheduled for Lu-177-PSMA-RLT, pretherapeutic estimated glomerular filtration rate (eGFR [ml/min/1.73 m² ]), Tc-99m-mercaptoacetyltriglycine (Tc-99m-MAG3) clearance and baseline Ga-68-PSMA-ligand positron emission tomography (PET)-derived renal cortical uptake and PSMA-tumor volume (TV) were determined. We tested the predictive capability of these parameters and clinical risk factors for the occurrence of CKD (defined as CTCAE vers. 5.0 grade 2 or higher) during follow-up.

RESULTS

After 4 ± 3 cycles of RLT average eGFR declined from 76 ± 17 to 72 ± 20 ml/min/1.73 m² (p = 0.003). Increased estimated renal radiation dose (eRRD) was significantly associated with renal functional decline (p = 0.008). During follow-up, 16/46 (30.4%) developed CKD grade 2 (no grade 3 or higher). In receiver operating characteristic (ROC) analysis, pretherapeutic eGFR was highly accurate in identifying the occurrence of CKD vs no CKD with an area under the curve (AUC) of 0.945 (p < 0.001; best threshold, 77 ml/min/1.73 m² ), followed by Tc-99m-MAG3-derived tubular extraction rate (TER; AUC, 0.831, p < 0.001; best threshold, 200 ml/min/1.73 m² ). Renal PET signal (p = 0.751) and PSMA-TV (p = 0.942), however, were not predictive. Kaplan-Meier analyses revealed adverse renal outcome for patients with lower eGFR (p = 0.001) and lower scintigraphy-derived TER (p = 0.009), with pretherapeutic eGFR emerging as the sole predictive parameter in multivariate analysis (p = 0.007).

CONCLUSION

Serious adverse renal events are not a frequent phenomenon after PSMA-targeted RLT. However, in patients developing moderate CKD after RLT, pretherapeutic eGFR is an independent predictor for renal impairment during follow-up.

Differences in Distribution and Detection Rate of the [68Ga]Ga-PSMA Ligands PSMA-617, -I&T and -11-Inter-Individual Comparison in Patients with Biochemical Relapse of Prostate Cancer

The biochemical relapse of prostate cancer is diagnostically challenging but of high clinical impact for subsequent patient treatment. PET/CT with radiolabeled PSMA ligands outperforms conventional diagnostic methods in the detection of tumor recurrence. Several radiopharmaceuticals were and are available for use. The aim of this study was to investigate whether the routinely applied [⁶⁸Ga]Ga-PSMA ligands PSMA-617, -I&T and -11 (HBED-CC) differ in physiological and pathological distribution, or in tumor detection rate. A retrospective evaluation of 190 patients (39 patients received PSMA-617, 68 patients PSMA-I&T and 83 patients PSMA-11) showed significant differences in tracer accumulation within all organs examined. The low retention within the compartments blood pool, bone and muscle tissue is a theoretical advantage of PSMA-11. Evaluation of tumor lesion uptake and detection rate did not reveal superiority of one of the three radiopharmaceuticals, neither in the whole population, nor in particularly challenging subgroups like patients with very low PSA levels. We conclude that all three [⁶⁸Ga]Ga-PSMA ligands are equally feasible in this clinically important scenario, and may replace each other in case of unavailability or production restrictions.

18F-PSMA-1007 PET in Biochemical Recurrent Prostate Cancer: An Updated Meta-Analysis

Background

Prostate-specific membrane antigen- (PSMA-) targeted agents labeled with fluorine-18 (¹⁸F) have recently become available to evaluate patients with biochemical recurrent prostate cancer (BRPCa) by using positron emission tomography/computed tomography (PET/CT) or positron emission tomography/magnetic resonance imaging (PET/MRI). We performed a systematic review and meta-analysis about the detection rate (DR) of ¹⁸F-PSMA-1007 PET/CT or PET/MRI in BRPCa patients.

Methods

A comprehensive computer literature search of PubMed/MEDLINE, EMBASE, and Cochrane Library databases for studies published through 17 May 2021 was carried out using the following search algorithm: “PSMA” AND “1007”. Only studies providing data on the DR of ¹⁸F-PSMA-1007 PET/CT or PET/MRI in BRPCa were included. A random-effects model was used to calculate the pooled DR on a per scan basis.

Results

Fifteen articles (853 patients) were selected and included in the systematic review, and ten were included in the quantitative analysis. Most of the studies reported a good DR of ¹⁸F-PSMA-1007 PET/CT or PET/MRI in BRPCa including also patients with low prostate-specific membrane antigen (PSA) values. The DR of ¹⁸F-PSMA-1007 PET/CT or PET/MRI was dependent on PSA serum values. The pooled DR was 81.3% (95% confidence interval: 74.6–88%) with statistical heterogeneity. A significant reporting bias (publication bias) was not detected.

Conclusions

¹⁸F-PSMA-1007 PET/CT or PET/MRI showed a good DR in BRPCa patients in line with other PSMA-targeted agents. The DR of ¹⁸F-PSMA-1007 PET/CT or PET/MRI is influenced by serum PSA values. These findings should be confirmed by prospective multicentric trials.

Clinical insignificance of [18F]PSMA-1007 avid non-specific bone lesions: a retrospective evaluation

PURPOSE

[18F]PSMA-1007 offers advantages of low urinary tracer excretion and theoretical improved spatial resolution for imaging prostate cancer. However, non-specific bone lesions (NSBLs), defined as mild to moderate focal bone uptake without a typical morphological correlate on CT, are a common finding on [18F]PSMA-1007 PET/CT. The purpose of this study was to investigate the clinical outcomes of patients with [18F]PSMA-1007 avid NSBLs, to determine whether patients with NSBLs represent a higher risk clinical cohort, and to determine whether SUVmax can be used as a classifier of bone metastasis.

METHODS

A retrospective audit of 214 men with prostate cancer was performed to investigate the clinical outcomes of [18F]PSMA-1007 avid NSBLs according to defined criteria. We also compared the serum PSA, Gleason score, and uptake time of patients with [18F]PSMA-1007 avid NSBLs to patients without [18F]PSMA-1007 avid bone lesions. Finally, we analysed an SUVmax threshold to identify bone metastases using ROC curve analysis.

RESULTS

Ninety-four of 214 patients (43.9%) demonstrated at least one NSBL. No [18F]PSMA-1007 avid NSBLs met criteria for a likely malignant or definitely malignant lesion after a median 15.8-month follow-up interval (11.9% definitely benign, 50.3% likely benign, and 37.7% equivocal). There were no statistically significant differences in serum PSA, Gleason score, and uptake time between patients with [18F]PSMA-1007 avid NSBLs and those without [18F]PSMA-1007 avid bone lesions. All NSBLs with adequate follow-up had SUVmax ≤ 11.1. The value of the highest SUVmax distinguished between NSBLs and definite prostate cancer bone metastases, whereby an SUVmax threshold of ≥ 7.2 maximized the Youden's index.

CONCLUSION

[18F]PSMA-1007 avid NSBLs rarely represent prostate cancer bone metastases. When identified in the absence of definite metastatic disease elsewhere, it is appropriate to classify those with SUVmax < 7.2 as likely benign. NSBLs with SUVmax 7.2-11.1 may be classified as equivocal or metastatic, with patient clinical risk factors, scan appearance, and potential management implications used to guide interpretation.

Enzymatic synthesis of fluorinated compounds

Fluorinated compounds are widely used in the fields of molecular imaging, pharmaceuticals, and materials. Fluorinated natural products in nature are rare, and the introduction of fluorine atoms into organic compound molecules can give these compounds new functions and make them have better performance. Therefore, the synthesis of fluorides has attracted more and more attention from biologists and chemists. Even so, achieving selective fluorination is still a huge challenge under mild conditions. In this review, the research progress of enzymatic synthesis of fluorinated compounds is summarized since 2015, including cytochrome P450 enzymes, aldolases, fluoroacetyl coenzyme A thioesterases, lipases, transaminases, reductive aminases, purine nucleoside phosphorylases, polyketide synthases, fluoroacetate dehalogenases, tyrosine phenol-lyases, glycosidases, fluorinases, and multienzyme system. Of all enzyme-catalyzed synthesis methods, the direct formation of the C-F bond by fluorinase is the most effective and promising method. The structure and catalytic mechanism of fluorinase are introduced to understand fluorobiochemistry. Furthermore, the distribution, applications, and future development trends of fluorinated compounds are also outlined. Hopefully, this review will help researchers to understand the significance of enzymatic methods for the synthesis of fluorinated compounds and find or create excellent fluoride synthase in future research.Key points• Fluorinated compounds are distributed in plants and microorganisms, and are used in imaging, medicine, materials science.• Enzyme catalysis is essential for the synthesis of fluorinated compounds.• The loop structure of fluorinase is the key to forming the C-F bond.

Intraindividual comparison of [68 Ga]-Ga-PSMA-11 and [18F]-F-PSMA-1007 in prostate cancer patients: a retrospective single-center analysis

BACKGROUND

The analysis aimed to compare the radiotracers [⁶⁸Ga]-Ga-PSMA-11 and [¹⁸F]-F-PSMA-1007 intraindividually in terms of malignant lesions, mi(molecular-imaging)TNM staging and presumable unspecific lesions retrospectively as used in routine clinical practice.

METHODS

A retrospective analysis of 46 prostate cancer patients (median age: 71 years) who underwent consecutive [⁶⁸Ga]-Ga-PSMA-11- and [¹⁸F]-F-PSMA-1007-PET/CT or PET/MRI within a mean of 12 ± 8.0 days was performed. MiTNM staging was performed in both studies by two nuclear medicine physicians who were blinded to the results of the other tracer. After intradisciplinary and interdisciplinary consensus with two radiologists was reached, differences in both malignant and presumable nonspecific tracer accumulation were analyzed.

RESULTS

Differences in terms of miTNM stages in both studies occurred in nine of the 46 patients (19.6%). The miT stages differed in five patients (10.9%), the miN stages differed in three patients (6.5%), and different miM stages occurred only in one patient who was upstaged in [¹⁸F]-F-PSMA-1007 PET. Concordant miTNM stages were obtained in 37 patients (80.4%). There was no significant difference between [¹⁸F]-F-PSMA-1007 and [⁶⁸Ga]-Ga-PSMA-11 in the SUV_max locally (31.5 vs. 32.7; p = 0.658), in lymph node metastases (28.9 vs. 24.9; p = 0.30) or in bone metastases (22.9 vs. 27.6; p = 0.286). In [¹⁸F]-F-PSMA-1007 PET, more patients featured presumable unspecific uptake in the lymph nodes (52.2% vs. 28.3%; p: < 0.001), bones (71.7% vs. 23.9%; p < 0.001) and ganglia (71.7% vs. 43.5%; p < 0.001). Probable unspecific, exclusively [¹⁸F]-F-PSMA-1007-positive lesions mainly occurred in the ribs (58.7%), axillary lymph nodes (39.1%) and cervical ganglia (28.3%).

CONCLUSION

In terms of miTNM staging, both tracers appeared widely exchangeable, as no tracer relevantly outperformed the other. The differences between the two tracers were far more common in presumable unspecific lesions than in malignant spots. A routinely performed two-tracer study could not be shown to be superior. Since it seems at least challenging for most nuclear medicine departments to provide both [¹⁸F]-F-PSMA-1007 and [⁶⁸Ga]-Ga-PSMA-11, it appears reasonable to choose the PSMA radiotracer depending on local availability with attention to the greater occurrence of nonspecific bone findings with [¹⁸F]-F-PSMA-1007.

Prospective intra-individual blinded comparison of [18F]PSMA-1007 and [68 Ga]Ga-PSMA-11 PET/CT imaging in patients with confirmed prostate cancer

INTRODUCTION

[¹⁸F]PSMA-1007 has potential advantages over [⁶⁸ Ga]Ga-PSMA-11, although limited prospective data evaluating diagnostic performance exist. The aims of this study are to describe the concordance of [¹⁸FPSMA-1007 and [⁶⁸ Ga]Ga-PSMA-11 for TNM with the American Joint Committee on Cancer (AJCC) prognostic stage and assess differences in tracer uptake.

METHODS

Fifty men (mean age 71.8) were imaged with [⁶⁸ Ga]Ga-PSMA-11 and [¹⁸F]PSMA-1007 < 4 weeks apart. Images were independently reported according to TNM by two experienced nuclear medicine specialists blinded to the other scan and prior imaging. Discordant results were resolved by a third independent nuclear medicine specialist. Quantitative analysis of lesion uptake and physiologic tissue for each tracer was performed by one experienced reader.

RESULTS

Scan indications were initial staging (n = 12), biochemical recurrence (n = 27) and metastatic disease evaluation (n = 11). Most patients had ISUP grade group 3 or higher. Median PSA value was 2.7 ng/ml (IQR 0.7-12.0), and a minority of patients (28%) were currently treated with androgen deprivation therapy. [¹⁸F]PSMA-1007 uptake was significantly higher than [⁶⁸Ga]Ga-PSMA-11 in local recurrence, nodal and distant metastases and most physiologic sites (including bone) except for urinary bladder which was significantly lower. [¹⁸F]PSMA-1007 upstaged local prostate staging in 5/17 patients, local recurrence in 3/33 patients, regional nodal disease in 3/50 patients and 1 distant metastasis (bladder). [⁶⁸Ga]Ga-PSMA-11 upstaged regional nodal disease in 1/50 patients and distant metastasis in one patient (right adrenal). Overall AJCC prognostic stage was concordant in 46/50 (92%) patients, with two patients upstaged for both [¹⁸F]PSMA-1007 and [⁶⁸Ga]Ga-PSMA-11. [¹⁸F]PSMA-1007 had more equivocal results (one regional node; six equivocal bone lesions, one of which was subsequently confirmed metastatic) than [⁶⁸Ga]Ga-PSMA-11 (one equivocal local recurrence).

CONCLUSION

Overall AJCC prognostic stage was similar (92%) between [¹⁸F]PSMA-1007 and [⁶⁸Ga]Ga-PSMA-11. [¹⁸F]PSMA-1007 demonstrates higher uptake within involved nodes and distant metastases and most physiologic sites except urinary bladder which aided [¹⁸F]PSMA-1007 local staging of the prostate primary/local recurrence and regional nodal disease adjacent ureters. However, [¹⁸F]PSMA-1007 liver uptake obscured a solitary right adrenal metastasis, and more equivocal bone lesions were identified. Trial registration The study was registered with Australia New Zealand Clinical Trials Registry (ACTRN12618000665235) on 24 April 2018.

An 89Zr-labeled PSMA tracer for PET/CT imaging of prostate cancer patients

The short half-life of existing prostate-specific membrane antigen (PSMA) tracers limits their time for internalization into tumor cells after injection, which is an essential prerequisite for robust detection of tumor lesions with low PSMA expression on PET/CT scans. Due to its longer half-life, the ⁸⁹Zr-labeled ligand ⁸⁹Zr-PSMA-Df allows acquisition of PET scans up to 6 days after injection, thereby overcoming the above limitation. We investigated whether ⁸⁹Zr-PSMA-Df allowed more sensitive detection of weak PSMA-positive prostate cancer lesions. Methods: We selected 14 prostate cancer patients with biochemical recurrence who exhibited no PSMA-positive lesions on a PET scan acquired with existing PSMA tracers (⁶⁸Ga-PSMA-11, ¹⁸F-JK-PSMA-7). Within 5 weeks after the negative scan, we performed a second PSMA-PET scan using ⁸⁹Zr-PSMA-Df (117±16 MBq, PET acquisition within 6 days of injection). Results: ⁸⁹Zr-PSMA-Df detected 15 PSMA-positive lesions in 8/14 patients, who had a PET-negative reading of their initial PET scans with existing tracers. In these 8 patients, the new scans revealed localized recurrence of disease (3/8), metastases in lymph nodes (3/8), or lesions at distant sites (2/8). Based on these results, patients received lesion-targeted radiotherapies (5/8), androgen deprivation therapies (2/8), or no therapy (1/8). The plausibility of 14/15 lesions was supported by histology, clinical follow-up after radiotherapy or subsequent imaging. Furthermore, comparison of the 15 ⁸⁹Zr-PSMA-Df-positive lesions with their correlates on the original PET scan revealed that established tracers exhibited mild accumulation in 7/15 lesions but contrast-to-noise ratios (CNR) were too low for robust detection of these lesions (CNR 2.4±3.7 for established tracers vs. 10.2±8.5 for ⁸⁹Zr-PSMA-Df, P = 0.0014). The SUV_max of the 15 ⁸⁹Zr-PSMA-Df-positive lesions (11.5±5.8) was significantly higher than the SUV_max on the original PET scans (4.7±2.8, P = 0.0001). Kidneys were the most exposed organ with doses of 3.3±0.7 mGy/MBq. The effective dose was 0.15±0.04 mSv/MBq. Conclusion: In patients with weak PSMA expression, a longer period of time might be needed for ligand internalization than that offered by existing PSMA tracers to make lesions visible on PET/CT scans. Hence, ⁸⁹Zr-PSMA-Df might be of significant benefit to patients in whom the search for weak PSMA-positive lesions is challenging. Radiation exposure should be weighed against the potential benefit of metastasis-directed therapy or salvage radiotherapy, which we initiated in 36% (5/14) of our patients based on their ⁸⁹Zr-PSMA-Df PET scans.

Parameters predicting [18F]PSMA-1007 scan positivity and type and number of detected lesions in patients with biochemical recurrence of prostate cancer

BACKGROUND

Detection of the site of recurrence using PSMA-PET/CT is important to guide treatment in patients with biochemical recurrence of prostate cancer (PCa). The aim of this study was to evaluate the positivity rate of [¹⁸F]PSMA-1007-PET/CT in patients with biochemically recurrent PCa and identify parameters that predict scan positivity as well as the type and number of detected lesions. This monocentric retrospective study included 137 PCa patients with biochemical recurrence who underwent one or more [¹⁸F]PSMA-1007-PET/CT scans between August 2018 and June 2019. PET-positive malignant lesions were classified as local recurrence, lymph node (LN), bone or soft tissue lesions. The association between biochemical/paraclinical parameters, as PSA value, PSA doubling time, PSA velocity, Gleason score (GS) and androgen deprivation therapy (ADT), and scan positivity as well as type and number of detected lesions was evaluated using logistic regression analysis (binary outcomes) and Poisson models (count-type outcomes).

RESULTS

We included 175 [¹⁸F]PSMA-1007-PET/CT scans after radical prostatectomy (78%), external beam radiation therapy (8.8%), ADT (7.3%), brachytherapy (5.1%) and high intensity focused ultrasound (0.7%) as primary treatment (median PSA value 1.6 ng/ml). Positivity rate was 80%. PSA value and PSA velocity were significant predictors of scan positivity as well as of the presence of bone and soft tissue lesions and number of bone, LN and soft tissue lesions, both in uni- and/or multivariable analysis. Multivariable analysis also showed prior ADT as predictor of bone and soft tissue lesions, GS as predictor of the number of bone lesions and ongoing ADT as predictor of the number of LN lesions.

CONCLUSION

[¹⁸F]PSMA-1007-PET/CT showed a high positivity rate in patients with biochemically recurrent PCa. PSA value and PSA velocity were significant predictors of scan positivity as well as of the presence and number of bone and soft tissue lesions and the number of LN lesions. Our findings can guide clinicians in optimal patient selection for [¹⁸F]PSMA-1007-PET/CT and support further research leading to the development of a prediction nomogram.

Synthesis, Preclinical Evaluation, and First-in-Human PET Study of Quinoline-Containing PSMA Tracers with Decreased Renal Excretion

The prostate-specific membrane antigen (PSMA) is considered to be an excellent theranostic target of prostate cancer (PCa). In this study, three 18F-labeled PSMA tracers with a more lipophilic quinoline functional spacer were designed, synthesized, and evaluated based on the Glu-Ureido-Lys binding motif. The effect of structure-related lipophilic difference on distribution and excretion of these tracers in vitro and in vivo (cells, rodent, primate, and human) was investigated by comparing with [18F]DCFPyL. There is no significant correlation between the renal elimination and the lipophilicity of the tracers in all species. However, the higher the lipophilicity of tracer, the higher the radioactivity accumulation in the liver of primate and human, and the less radioactivity is to excrete to the bladder with urine. The screened tracer [18F]8c, with a Ki value of 4.58 nM, displayed notable low bladder retention and demonstrated good imaging properties in patients with PCa.

Development and Validation of a GMP-Compliant High-Pressure Liquid Chromatography Method for the Determination of the Chemical and Radiochemical Purity of [18F]PSMA-1007, a PET Tracer for the Imaging of Prostate Cancer

For the PET imaging of prostate cancer, radiotracers targeting the prostate-specific membrane antigen (PSMA) are nowadays used in clinical practice. [¹⁸F]PSMA-1007, a radiopharmaceutical labeled with fluorine-18, has excellent properties for the detection of prostate cancer. Essential for the human use of a radiotracer is its production and quality control under GMP-compliance. For this purpose, all analytical methods have to be validated. [¹⁸F]PSMA-1007 is easily radiosynthesized in a one-step procedure and isolated using solid phase extraction (SPE) cartridges followed by formulation of a buffered injection solution and for the determination of its chemical and radiochemical purity a robust, fast and reliable quality control method using radio-HPLC is necessary. After development and optimizations overcoming problems in reproducibility, the here described radio-HPLC method fulfills all acceptance criteria—for e.g., specificity, linearity, and accuracy—and is therefore well suited for the routine quality control of [¹⁸F]PSMA-1007 before release of the radiopharmaceutical. Recently a European Pharmacopeia monograph for [¹⁸F]PSMA-1007 was published suggesting a different radio-HPLC method for the determination of its chemical and radiochemical purity. Since the here described method has certain advantages, not least of all easier technical implementation, it can be an attractive alternative to the monograph method. The here described method was successfully validated on several radio-HPLC systems in our lab and used for the analysis of more than 60 batches of [¹⁸F]PSMA-1007. Using this method, the chemical and radiochemical purity of [¹⁸F]PSMA-1007 can routinely be evaluated assuring patient safety.