PSA-Stratified Performance of 18F- and 68Ga-PSMA PET in Patients with Biochemical Recurrence of Prostate Cancer

Comparison of 18F-based PSMA radiotracers with [68Ga]Ga-PSMA-11 in PET/CT imaging of prostate cancer-a systematic review and meta-analysis

BACKGROUND

Prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) has become an increasingly established imaging modality in the staging of prostate cancer (PCa). Numerous PSMA-based tracers are currently available, however, there is a lack of consensus on the optimal radiotracer(s) for PSMA PET/CT. This study aims to investigate whether Fluorine-18 (18F)-labelled PSMA PET/CT is significantly different from Gallium-68 (68Ga) in primary diagnosis and/or secondary staging of prostate cancer following biochemical recurrence.

METHODS

A critical review of MEDLINE, EMBASE, PubMed and Web of Science databases was performed in May 2023 according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement. Studies that directly compared 18F-based PSMA radiotracers and [68Ga]Ga-PSMA-11 in terms of the normal organ SUV or the lesion SUV or the detection rate were assessed. Quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2).

RESULTS

Twenty-four studies were analysed. [18F]DCFPyL and [18F]PSMA-1007 were the two most commonly studied 18F based PSMA tracers. [18F]JK-PSMA-7, [18F]rhPSMA-7, [18F]AlF-PSMA-11 were the new tracers evaluated in a limited number of studies. Overall, [18F]DCFPyL was observed to have a similar lesion detection rate to [68Ga]Ga-PSMA-11 with no increase in false positive rates. [18F]PSMA-1007 was found to have a greater local lesion detection rate because of its predominant hepatobiliary excretory route. However, [68Ga]Ga-PSMA-11 was observed to have a similar local lesion detection rate in studies that administer patients with furosemide prior to the scan. In addition, [18F]PSMA-1007 was found to have a significant number of benign bone uptakes.

CONCLUSIONS

[18F]DCFPyL was observed to be similar to [68Ga]Ga-PSMA-11. [18F]PSMA-1007 was observed to be less preferrable to [68Ga]Ga-PSMA-11 due to its high benign bone uptakes. Overall, there was not enough evidence in differentiating the radiotracers based on their clinical impacts.

The Application of Prostate Specific Membrane Antigen in the Diagnosis and Treatment of Prostate Cancer: Status and Challenge

In recent years, the incidence of prostate cancer has been increasing globally. Early stage of the disease can obtain a better clinical prognosis from surgery and endocrine therapy. The progression of advanced stage varies significantly between individuals, with some patients developing metastatic castration-resistant prostate cancer after standardized treatment. Therefore, staging of prostate cancer by accurate imaging is particularly important for the clinical management of patients. Simultaneously, the development of targeted therapy is also urgent for the treatment of advanced prostate cancer. Prostate specific membrane antigen as a prostate specific target has been widely used in the diagnosis and treatment of prostate cancer. This review summarizes the latest research progress of targeted prostate specific membrane antigen in the diagnosis and treatment of prostate cancer in detail, analyzes their value and challenges.

Update on PSMA-based Prostate Cancer Imaging

The increased use of prostate-specific membrane antigen (PSMA) based PET imaging for prostate cancer (Pca) detection has revolutionized the clinical management of Pca, with higher diagnostic sensitivity for extraprostatic disease and increasing clinical utility across different stages of the disease. The integration of PSMA PET imaging into clinical guidelines and consensus documents reflects its growing importance in the personalized management of Pca. This review of recent literature highlights the rapid evolution of PSMA PET into the mainstream of staging and restaging and the decreasing reliance on conventional imaging modalities. This comprehensive review serves as a resource for clinicians and researchers involved in the domains of Pca diagnosis and management.

Prostate Cancer Recurrence: Examining the Role of Salvage Radiotherapy Field and Risk Factors for Regional Disease Recurrence Captured on 18F-DCFPyL PET/CT

PURPOSE

The role of elective pelvic nodal irradiation in salvage radiotherapy (sRT) remains controversial. Utilizing 18F-DCFPyL PET/CT, this study aimed to investigate differences in disease distribution after whole pelvic (WPRT) or prostate bed (PBRT) radiotherapy and to identify risk factors for pelvic lymph node (LN) relapse.

METHODS

This retrospective study included patients with PSA > 0.1 ng/mL post-radical prostatectomy (RP) or post-RP and sRT who underwent 18F-DCFPyL PET/CT. Disease distribution on 18F-DCFPyL PET/CT after sRT was compared using Chi-square tests. Risk factors were tested for association with pelvic LN relapse after RP and salvage PBRT using logistic regression.

RESULTS

979 18F-DCFPyL PET/CTs performed at our institution between 1/1/2022 - 3/24/2023 were analyzed. There were 246 patients meeting criteria, of which 84 received salvage RT after RP (post-salvage RT group) and 162 received only RP (post-RP group). Salvage PBRT patients (n = 58) had frequent pelvic nodal (53.6%) and nodal-only (42.6%) relapse. Salvage WPRT patients (n = 26) had comparatively lower rates of pelvic nodal (16.7%, p = 0.002) and nodal-only (19.2%, p = 0.04) relapse. The proportion of distant metastases did not differ between the two groups. Multiple patient characteristics, including ISUP grade and seminal vesicle invasion, were associated with pelvic LN disease in the post-RP group.

CONCLUSION

At PSA persistence or progression, salvage WPRT resulted in lower rates of nodal involvement than salvage PBRT, but did not reduce distant metastases. Certain risk factors increase the likelihood of pelvic LN relapse after RP and can help inform salvage RT field selection.

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.

Prostate-specific Membrane Antigen: Diagnostics

Since its clinical introduction in May 2011, prostate-specific membrane antigen (PSMA)-PET/computed tomography has quickly gained worldwide recognition as a significant breakthrough in prostate cancer diagnostics. In the meantime, several new PSMA radioligands for PET imaging have been introduced into routine clinical practice. This article aims to introduce the most commonly used tracers and their key areas of application.

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.

Application of next-generation imaging in biochemically recurrent prostate cancer

BACKGROUND

Biochemical recurrence (BCR) following primary interventional treatment occurs in approximately one-third of patients with prostate cancer (PCa). Next-generation imaging (NGI) can identify local and metastatic recurrence with greater sensitivity than conventional imaging, potentially allowing for more effective interventions. This narrative review examines the current clinical evidence on the utility of NGI for patients with BCR.

METHODS

A search of PubMed was conducted to identify relevant publications on NGI applied to BCR. Given other relevant recent reviews on the topic, this review focused on papers published between January 2018 to May 2023.

RESULTS

NGI technologies, including positron emission tomography (PET) radiotracers and multiparametric magnetic resonance imaging, have demonstrated increased sensitivity and selectivity for diagnosing BCR at prostate-specific antigen (PSA) concentrations <2.0 ng/ml. Detection rates range between 46% and 50%, with decreasing PSA levels for choline (1-3 ng/ml), fluciclovine (0.5-1 ng/ml), and prostate-specific membrane antigen (0.2-0.49 ng/ml) PET radiotracers. Expert working groups and European and US medical societies recommend NGI for patients with BCR.

CONCLUSIONS

Available data support the improved detection performance and selectivity of NGI modalities versus conventional imaging techniques; however, limited clinical evidence exists demonstrating the application of NGI to treatment decision-making and its impact on patient outcomes. The emergence of NGI and displacement of conventional imaging may require a reexamination of the current definitions of BCR, altering our understanding of early recurrence. Redefining the BCR disease state by formalizing the role of NGI in patient management decisions will facilitate greater alignment across research efforts and better reflect the published literature.

First-in-human study of PSMA-targeting agent, [18F]AlF-P16-093: dosimetry and initial evaluation in prostate cancer patients

PURPOSE

This is a first-in-human study to evaluate the radiation dosimetry of a new prostate-specific membrane antigen (PSMA)-targeted radiopharmaceutical, [18F]AlF-P16-093, and also initial investigation of its ability to detect PSMA-positive tumors using PET scans in a cohort of prostate cancer (PCa) patients.

METHODS

The [18F]AlF-P16-093 was automatically synthesized with a GE TRACERlab. A total of 23 patients with histopathologically proven PCa were prospectively enrolled. Dosimetry and biodistribution study investigations were carried out on a subset of six (6) PCa patients, involving multiple time-point scanning. The mean absorbed doses were estimated with PMOD and OLINDA software.

RESULTS

[18F]AlF-P16-093 was successfully synthesized, and radiochemical purity was > 95%, and average labeling yield was 36.5 ± 8.3% (decay correction, n = 12). The highest tracer uptake was observed in the kidneys, spleen, and liver, contributing to an effective dose of 16.8 ± 1.3 μSv/MBq, which was ~ 30% lower than that of [68Ga]Ga-P16-093. All subjects tolerated the PET examination well, and no reportable side-effects were observed. The PSMA-positive tumors displayed rapid uptake, and they were all detectable within 10 min, and no additional lesions were observed in the following multi-time points scanning. Each patient had at least one detectable tumor lesion, and a total of 356 tumor lesions were observed, including intraprostatic, lymph node metastases, bone metastases, and other soft tissue metastases.

CONCLUSIONS

We report herein a streamlined method for high yield synthesis of [18F]AlF-P16-093. Preliminary study in PCa patients has demonstrated its safety and acceptable radiation dosimetry. The initial diagnostic study indicated that [18F]AlF-P16-093 PET/CT is efficacious and potentially useful for a widespread application in the diagnosis of PCa patients.

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.

Clinical Positron Emission Tomography/Computed Tomography: Quarter-Century Transformation of Prostate Cancer Molecular Imaging

Although positron emission tomography/computed tomography (PET/CT) underwent rapid growth during the last quarter-century, becoming a new standard-of-care for imaging most cancer types, CT and bone scan remained the gold standard for patients with prostate cancer. This occurred as 2-fluorine-18-fluoro-2-deoxy-d-glucose was perceived to have a limited role owing to low sensitivity in many patients. A resurgence of interest occurred with the use of fluorine-18-sodium-fluoride PET/CT as a replacement for bone scintigraphy, and then choline, fluciclovine, and dihydrotestosterone (DHT) PET/CT as prostate "specific" radiotracers. The last decade, however, has seen a true revolution with the meteoric rise of prostate-specific membrane antigen PET/CT.

Prostate-specific membrane antigen-positron emission tomography (PSMA-PET) of prostate cancer: current and emerging applications

Prostate-specific membrane antigen-positron emission tomography (PSMA-PET) is transforming the management of patients with prostate cancer. In appropriately selected patients, PSMA-PET offers superior sensitivity and specificity compared to conventional imaging (e.g., computed tomography and bone scintigraphy) as well as choline and fluciclovine PET, with the added benefit of consolidating bone and soft tissue evaluation into a single study. Despite being a newly available imaging tool, PSMA-PET has established indications, interpretation guidelines, and reporting criteria, which will be reviewed. The prostate cancer care team, from imaging specialists to those delivering treatment, should have knowledge of physiologic PSMA radiotracer uptake, patterns of disease spread, and the strengths and limitations of PSMA-PET. In this review, current and emerging applications of PSMA-PET, including appropriateness use criteria as well as image interpretation and pitfalls, will be provided with an emphasis on clinical implications.

Phase I/IIa trial of 18F-prostate specific membrane antigen (PSMA) 1007 PET/CT in healthy volunteers and prostate cancer patients

OBJECTIVE

18F-PSMA 1007 is a promising PET tracer for prostate cancer. We aimed to examine the safety, biodistribution, radiation dosimetry, and clinical effectiveness in Japanese healthy volunteers and patients with prostate cancer.

METHODS

Part A evaluated the pharmacokinetics and exposure doses in three healthy volunteers. Part B evaluated the diagnostic accuracy in patients with untreated preoperative prostate cancer (Cohort 1, n = 7) and patients with biochemical recurrence (Cohort 2, n = 3). All subjects received a single dose of 3.7 MBq/kg 18F-PSMA 1007. Results: 18F-PSMA 1007 was found to be safe and well tolerated in all subjects. No serous AEs or drug-related AEs were identified during the present study. The average blood radioactivity concentration reached a maximum of 47.87 ± 1.05 (percentage of injected dose [%ID]/ml) at 5 min and then decreased to 1.60 ± 0.78 in 6 h. The systemic radioactivity reached a maximum of 211.05 ± 6.77 (%ID$\times$103) at 5 min and decreased to 7.18 ± 3.91 in 6 h. The sensitivity and positive predictive value were 100% and 100% based on both pathologic and imaging confirmation as gold standard. In Cohort 1, 15 primary foci (11.9%) were >5 mm in the largest diameter and identified in 39 of 126 segments (30.1%). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for 60 min uptake time acquisition were 80.0, 96.5, 91.4, 91.2 and 91.3%, respectively.

CONCLUSIONS

Our study revealed that 18F-PSMA 1007 was safe, well tolerated and showed high accuracy in the diagnosis of prostate cancer.

Optimization and scale up of production of the PSMA imaging agent [18F]AlF-P16-093 on a custom automated radiosynthesis platform

BACKGROUND

Recent advancements in positron emission tomograph (PET) using prostate specific membrane antigen (PSMA)-targeted radiopharmaceuticals have changed the standard of care for prostate cancer patients by providing more accurate information during staging of primary and recurrent disease. [68Ga]Ga-P16-093 is a new PSMA-PET radiopharmaceutical that demonstrated superior imaging performance in recent head-to-head studies with [68Ga]Ga-PSMA-11. To improve the availability of this new PSMA PET imaging agent, [18F]AlF-P16-093 was developed. The 18F-analog [18F]AlF-P16-093 has been synthesized manually at low activity levels using [18F]AlF2+ and validated in pre-clinical models. This work reports the optimization of the production of > 15 GBq of [18F]AlF-P16-093 using a custom automated synthesis platform.

RESULTS

The sensitivity of the radiochemical yield of [18F]AlF-P16-093 to reaction parameters of time, temperature and reagent amounts was investigated using a custom automated system. The automated system is a low-cost, cassette-based system designed for 1-pot syntheses with flow-controlled solid phase extraction (SPE) workup and is based on the Raspberry Pi Zero 2 microcomputer/Python3 ecosystem. The optimized none-decay-corrected yield was 52 ± 4% (N = 3; 17.5 ± 2.2 GBq) with a molar activity of 109 ± 14 GBq/µmole and a radiochemical purity of 98.6 ± 0.6%. Run time was 30 min. A two-step sequence was used: SPE-purified [18F]F- was reacted with 80 nmoles of freeze-dried AlCl3·6H2O at 65 °C for 5 min followed by reaction with 160 nmoles of P16-093 ligand at 40 °C for 4 min in a 1:1 mixture of ethanol:0.5 M pH 4.5 NaOAc buffer. The mixture was purified by SPE (> 97% recovery). The final product formulation (5 mM pH 7 phosphate buffer with saline) exhibited a rate of decline in radiochemical purity of ~ 1.4%/h which was slowed to ~ 0.4%/h when stored at 4 °C.

CONCLUSION

The optimized method using a custom automated system enabled the efficient (> 50% none-decay-corrected yield) production of [18F]AlF-P16-093 with high radiochemical purity (> 95%). The method and automation system are simple and robust, facilitating further clinical studies with [18F]AlF-P16-093.

Circulating and Imaging Biomarkers of Radium-223 Response in Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Radium-223 improves overall survival (OS) and reduces skeletal events in patients with bone metastatic castration-resistant prostate cancer (CRPC), but relevant biomarkers are lacking. We evaluated automated bone scan index (aBSI) and circulating tumor cell (CTC) analyses as potential biomarkers of prognosis and activity.

PATIENTS AND METHODS

Patients with bone metastatic CRPC were enrolled on a prospective single-arm study of standard radium-223. 99mTc-MDP bone scan images at baseline, 2 months, and 6 months were quantitated using aBSI. CTCs at baseline, 1 month, and 2 months were enumerated and assessed for RNA expression of prostate cancer-specific genes using microfluidic enrichment followed by droplet digital polymerase chain reaction.

RESULTS

The median OS was 21.3 months in 22 patients. Lower baseline aBSI and minimal change in aBSI (<+0.7) from baseline to 2 months were each associated with better OS (P = .00341 and P = .0139, respectively). The higher baseline CTC count of ≥5 CTC/7.5 mL was associated with worse OS (median, 10.1 v 32.9 months; P = .00568). CTCs declined at 2 months in four of 15 patients with detectable baseline CTCs. Among individual genes in CTCs, baseline expression of the splice variant AR-V7 was significantly associated with worse OS (hazard ratio, 5.20 [95% CI, 1.657 to 16.31]; P = .00195). Baseline detectable AR-V7, higher aBSI, and CTC count ≥5 CTC/7.5 mL continued to have a significant independent negative impact on OS after controlling for prostate-specific antigen or alkaline phosphatase.

CONCLUSION

Quantitative bone scan assessment with aBSI and CTC analyses are prognostic markers in patients treated with radium-223. AR-V7 expression in CTCs is a particularly promising prognostic biomarker and warrants validation in larger cohorts.

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.

Application of Advanced Imaging to Prostate Cancer Diagnosis and Management: A Narrative Review of Current Practice and Unanswered Questions

Major advances in prostate cancer diagnosis, staging, and management have occurred over the past decade, largely due to our improved understanding of the technical aspects and clinical applications of advanced imaging, specifically magnetic resonance imaging (MRI) and prostate-cancer-specific positron emission tomography (PET). Herein, we review the established utility of these important and exciting technologies, as well as areas of controversy and uncertainty that remain important areas for future study. There is strong evidence supporting the utility of MRI in guiding initial biopsy and assessing local disease. There is debate, however, regarding how to best use the imaging modality in risk stratification, treatment planning, and assessment of biochemical failure. Prostate-cancer-specific PET is a relatively new technology that provides great value to the evaluation of newly diagnosed, treated, and recurrent prostate cancer. However, its ideal use in treatment decision making, staging, recurrence detection, and surveillance necessitates further research. Continued study of both imaging modalities will allow for an improved understanding of their best utilization in improving cancer care.

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.

Using 18F-DCFPyL Prostate-Specific Membrane Antigen-Directed Positron Emission Tomography/Magnetic Resonance Imaging to Define Intraprostatic Boosts for Prostate Stereotactic Body Radiation Therapy

Purpose

The recently reported FLAME trial demonstrated a biochemical disease-free survival benefit to using a focal intraprostatic boost to multiparametric magnetic resonance imaging (mpMRI)-identified lesions in men with localized prostate cancer treated with definitive radiation therapy. Prostate-specific membrane antigen (PSMA)-directed positron emission tomography (PET) may identify additional areas of disease. In this work, we investigated using both PSMA PET and mpMRI in planning focal intraprostatic boosts using stereotactic body radiation therapy (SBRT).

Methods and Materials

We evaluated a cohort of patients (n = 13) with localized prostate cancer who were imaged with 2-(3-(1-carboxy-5-[(6-[18F]fluoro-pyridine-2-carbonyl)-amino]-pentyl)-ureido)-pentanedioic acid (¹⁸F-DCFPyL) PET/MRI on a prospective imaging trial before undergoing definitive therapy. The number of lesions concordant (overlapping) and discordant (no overlap) on PET and MRI was assessed. Overlap between concordant lesions was evaluated using the Dice and Jaccard similarity coefficients. Prostate SBRT plans were created fusing the PET/MRI imaging to computed tomography scans acquired the same day. Plans were created using only MRI-identified lesions, only PET-identified lesions, and the combined PET/MRI lesions. Coverage of the intraprostatic lesions and doses to the rectum and urethra were assessed for each of these plans.

Results

The majority of lesions (21/39, 53.8%) were discordant between MRI and PET, with more lesions seen by PET alone (12) than MRI alone (9). Of lesions that were concordant between PET and MRI, there were still areas that did not overlap between scans (average Dice coefficient, 0.34). Prostate SBRT planning using all lesions to define a focal intraprostatic boost provided the best coverage of all lesions without compromising constraints on the rectum and urethra.

Conclusions

Using both mpMRI and PSMA-directed PET may better identify all areas of gross disease within the prostate. Using both imaging modalities could improve the planning of focal intraprostatic boosts.

Application of targeted diagnosis of PSMA in the modality shift of prostate cancer diagnosis: a review

Prostate cancer (PCa) is a serious threat to the health of men all over the world. The progression of PCa varies greatly among different individuals. In clinical practice, some patients often progress to advanced PCa. Therefore, accurate imaging for diagnosis and staging of PCa is particularly important for clinical management of patients. Conventional imaging examinations such as MRI and CT cannot accurately diagnose the pathological stages of advanced PCa, especially metastatic lymph node (LN) stages. As a result, developing an accurate molecular targeted diagnosis is crucial for advanced PCa. Prostate specific membrane antigen (PSMA) is of great value in the diagnosis of PCa because of its specific expression in PCa. At present, researchers have developed positron emission tomography (PET) targeting PSMA. A large number of studies have confirmed that it not only has a higher tumor detection rate, but also has a higher diagnostic efficacy in the pathological stage of advanced PCa compared with traditional imaging methods. This review summarizes recent studies on PSMA targeted PET in PCa diagnosis, analyzes its value in PCa diagnosis in detail, and provides new ideas for urological clinicians in PCa diagnosis and clinical management.

What's to come in PSMA therapies and diagnostics: A summary of clinical trials involving PSMA radioligand-based therapeutic and/or diagnostic approaches with active recruitment

INTRODUCTION

Prostate-Specific Membrane Antigen (PSMA)-based diagnostics and therapeutics are proving highly valuable in identifying disease sites and providing targeted radioligand therapy (RLT) for disseminated disease in prostate cancer (PC). With successful integration of these tools in limited PC presentations, there is a real need and excitement for trials testing PSMA-based approaches more broadly.

AREAS COVERED

We review the ongoing trials registered on ClinicalTrials.gov which aim to evaluate PSMA-PET or PSMA-RLT applications. We outline clinical contexts which have significant ongoing study and therefore may see imminent change, as well as contexts which are lacking in study in the hopes of guiding future research.

EXPERT OPINION

Trials examining intensification strategies through targeted radiotherapy, combination systemic therapies, and RLTs have the potential to demonstrate improved clinical outcomes using PSMA-PET CT for guidance. We expect that PSMA-PET will become fundamental in the work-up of patients before targeted radiotherapy or surgery. The results of ongoing trials will likely clarify the benefits of PSMA-RLT in metastatic PC including in oligometastatic and hormone-sensitive disease; however, there is a sparsity of trials evaluating PSMA-RLT outside of metastatic PC. Clinical trials with PSMA PET/CT as an endpoint for disease control are emerging and standardized reporting and metrics for PSMA staging and response will facilitate the inclusion of PSMA PET endpoints into therapeutic trials.

Synthesis and Evaluation of 99mTc-Labeled PSMA-Targeted Tracers Based on the Lys-Urea-Aad Pharmacophore for Detecting Prostate Cancer with Single Photon Emission Computed Tomography

Prostate-specific membrane antigen (PSMA) is a well-validated prostate cancer marker but reported PSMA-targeted tracers derived from the Lys-urea-Glu pharmacophore including the clinically validated [^99mTc]Tc-EDDA/HYNIC-iPSMA have high off-target uptake in kidneys, spleen, and salivary glands. In this study, we synthesized and evaluated three novel ^99mTc-labeled PSMA-targeted tracers and investigated if the tracers derived from the Lys-urea-Aad pharmacophore could have minimized uptake in off-target organs/tissues. In vitro competition binding assays showed that compared with HYNIC-iPSMA, the three novel ligands had slightly weaker PSMA binding affinity (average K_i = 3.11 vs. 8.96-11.6 nM). Imaging and ex vivo biodistribution studies in LNCaP tumor-bearing mice showed that [^99mTc]Tc-EDDA/HYNIC-iPSMA and the three novel tracers successfully visualized LNCaP tumor xenografts in SPECT images and were excreted mainly via the renal pathway. The average tumor uptake at 1 h post-injection varied from 5.40 to 18.8%ID/g, and the tracers derived from the Lys-urea-Aad pharmacophore had much lower uptake in the spleen and salivary glands. Compared with the clinical tracer [^99mTc]Tc-EDDA/HYNIC-iPSMA, the Lys-urea-Aad-derived [^99mTc]Tc-EDDA-KL01127 had lower background uptake and superior tumor-to-background contrast ratios and is therefore promising for clinical translation to detect prostate cancer lesions with SPECT.

ACR Appropriateness Criteria® Post-Treatment Follow-up of Prostate Cancer: 2022 Update

Prostate cancer has a wide spectrum ranging between low-grade localized disease and castrate-resistant metastatic disease. Although whole gland and systematic therapies result in cure in the majority of patients, recurrent and metastatic prostate cancer can still occur. Imaging approaches including anatomic, functional, and molecular modalities are continuously expanding. Currently, recurrent and metastatic prostate cancer is grouped in three major categories: 1) Clinical concern for residual or recurrent disease after radical prostatectomy, 2) Clinical concern for residual or recurrent disease after nonsurgical local and pelvic treatments, and 3) Metastatic prostate cancer treated by systemic therapy (androgen deprivation therapy, chemotherapy, immunotherapy). This document is a review of the current literature regarding imaging in these settings and the resulting recommendations for imaging. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Comparing digital to analog prostate-specific membrane antigen-targeted piflufolastat 18 F PET/CT in prostate cancer patients in early biochemical failure

PURPOSE

Prostate-specific membrane antigen (PSMA) positron emission tomography/computer tomography (PET/CT) in prostate cancer patients with biochemical failure(BCF) showslimited sensitivity when the prostate-specific antigen(PSA) <0.5 ng/mL. The development of digital PET/CT has greatly improved smaller lesion detection. This study's goal was to compare the performance and clinical value of PSMA-targeted piflufolastat PET/CT for prostate cancer BCF with digital versus analog PET/CT.

METHODS

In this retrospective study, all piflufolastat PET/CT scans in subjects with PSA ≤ 3.0 ng/mL who were referred for prostate cancer BCF were included. The performance characteristics of 171 analog PET/CT studies in 155 subjects from May 2017 to January 2020 and 106 digital PET/CT studies in 103 subjects from February 2020 to December 2020 were compared. Lesions were considered malignant if they did not match the known physiological distribution of piflufolastat and did not represent uptake in benign lesions. PSMA PET/CT studies were considered positive if at least one malignant lesion was detected and negative if none were detected.

RESULTS

Digital piflufolastat PET/CT outperformed analog piflufolastat PET/CT in subjects with PSA < 0.5 ng/mL with a positivity rate of 69% versus 37%, respectively. In patients with PSA ≥ 0.5 ng/mL, both technologies performed similarly. There was no statistically significant difference between the number or size of piflufolastat-avid lesions detected per PET/CT study.

CONCLUSION

In prostate cancer patients with BCF and PSA < 0.5 ng/mL, digital piflufolastat PET/CT has a higher detection rate of malignant lesions than analog piflufolastat PET/CT.

Development of a high-performance liquid chromatography method for rapid radiochemical purity measurement of [18 F]PSMA-1007, a PET radiopharmaceutical for detection of prostate cancer

Since first becoming commercially available in 2018, the PET radiopharmaceutical [¹⁸ F]PSMA-1007 has been used widely for the diagnosis and staging of prostate cancer. A pharmacopoeia monograph first became available in 2021, prescribing a radiochemical purity specification of >91%, based on analytical results from both TLC (for [¹⁸ F]fluoride impurity alone) and HPLC (for all other ¹⁸ F-impurities). Though this monograph has provided clarity for the quality control testing of [¹⁸ F]PSMA-1007, it prescribes a HPLC method using phosphate buffer mobile phase that may present a risk of precipitation of phosphate salts in the HPLC system. The method also requires specialised hardware not immediately available to all laboratories. This work describes the development of a simple, rapid reversed-phase HPLC method utilising 0.1 M ammonium formate mobile phase for the accurate assessment of both [¹⁸ F]fluoride impurity and overall radiochemical purity in a single test. This method is especially useful for assessment of product stability over time. A more accurate TLC method for [¹⁸ F]fluoride impurity is also described.

PSMA-PET/CT-Guided Intensification of Radiation Therapy for Prostate Cancer (PSMAgRT): Findings of Detection Rate, Effect on Cancer Management, and Early Toxicity From a Phase 2 Randomized Controlled Trial

PURPOSE

Prostate-specific membrane antigen (PSMA) ligand positron emission tomography (PET) is increasingly integrated in prostate cancer management because of its diagnostic performance. We sought to evaluate the effect of PSMA-PET/computed tomography (CT)-guided intensification of radiation therapy (PSMAgRT) on patient outcomes. Here, we report secondary trial endpoints including the rate of new lesion detection, effect on prostate cancer management, and treatment-related toxicities.

METHODS AND MATERIALS

In this phase 2 cohort multiple randomized controlled trial across 2 institutions, men with prostate cancer planned for RT were randomly selected for PSMAgRT across 4 strata: oligometastatic, high risk (Cancer of the Prostate Risk Assessment ≥6 or cN1), salvage post-RT, and salvage postprostatectomy (RP). Primary endpoint was failure-free survival at 5 years, with analysis pending further follow-up. Secondary endpoints included new lesion detection yield of PSMA-PET/CT, acute and delayed toxicities, effect on prostate cancer management, and health-related quality-of-life outcomes. This trial is registered with ClinicalTrials.gov, identifier NCT03525288, companion to registry NCT03378856.

RESULTS

Between May 2018 and February 2021, 262 patients were enrolled and randomized. Nine patients were later excluded (5 control, 4 PSMAgRT), leaving 253 patients for analysis (23 oligometastatic, 86 high risk, 16 salvage post-RT, and 128 salvage post-RP). New lesions were detected in 45.5% of oligometastatic, 39.5% of high risk, 14.3% of salvage post-RT, and 51.6% of salvage post-RP. Overall, PSMA-PET/CT led to intensification of RT in over half of patients (52.0%), with minimal intensification of systemic therapy (4.0%). With a median follow-up of 12.9 months, this intensification was associated with 3 attributable grade 3+ events (2.5% of patients undergoing PSMAgRT) but no difference in the rate of grade 2+ events attributable to RT compared with controls (43%, both arms).

CONCLUSIONS

In this randomized trial, PSMA-PET/CT led to intensification of RT in more than half of patients. Longer follow-up is required to determine whether this intensification translates to effect on cancer control and long-term toxicity and health-related quality-of-life outcomes.

68Ga-PSMA PET/CT in early relapsed prostate cancer patients after radical therapy

Biochemical recurrence (BCR) of prostate cancer (PCa) occurs in about 25% of patients treated with radical prostatectomy (RP) and up to 45% in patients who receive external beam radiotherapy (RT). Early diagnosis of PCa recurrence is of high importance for successful salvage therapy. The aim of the present study is to analyze the efficacy of ⁶⁸ Ga-PSMA PET/CT in detecting the presence of local and/or systemic disease in patients with a history of PCa who have BCR. A total of 52 PCa patients with BCR referred for ⁶⁸ Ga-PSMA PET/CT were recruited from the American University of Beirut Medical Center between November 2017 and December 2019. We compared the performance of PSMA PET/CT to the results and clinical factors based on follow up: PSA, PSA kinetics, primary treatment, and Gleason score. The relationship between the PET/CT findings and clinical indicators of disease were assessed by univariate and multivariate logistic regression. From a total of 52 patients, 34 (65.4%) had positive PSMA-PET/CT scans. Among those, 8/34 (23.5%) received primary RT. For all patients with a positive PSMA-PET: the detection rate was 2/4 (50%) for PSA < 0.2, 5/10 (50%) for PSA 0.2-0.49, 3/6 (50%) for PSA 0.5-0.99, 6/12 (50%) for PSA 1-1.99, 8/9 (88.9%) for PSA 2-3.99, and 10/11 (90.9%) for PSA 4-10.PSMA-PET/CT positivity was significantly associated with PSA level at time of PET scan, PSA doubling time, Gleason score and TNM staging. However, it did not show a significant correlation with radiotherapy as primary treatment, ongoing androgen deprivation therapy (ADT), time to relapse, and initial PSA before therapy. In our single center prospective trial, ⁶⁸ Ga-PSMA PET/CT successfully detected the recurrence of PCa in patients with BCR. Scan positivity was significantly associated with PSA level at time of PET scan, PSA doubling time, Gleason score, and TNM staging. PSMA- PET/CT is a highly promising modality in the work up of patients with PCa in the setting of BCR for earlier detection of disease recurrence.

Comparing the diagnostic performance of radiotracers in prostate cancer biochemical recurrence: a systematic review and meta-analysis

OBJECTIVES

To systematically assess the early detection rate of biochemical prostate cancer recurrence using choline, fluciclovine, and PSMA.

METHODS

Under the guidance of the Preferred Reporting Items for Systematic reviews and Meta-Analysis Diagnostic Test Accuracy guidelines, literature that assessed the detection rates (DRs) of choline, fluciclovine, and PSMA in prostate cancer biochemical recurrence was searched in PubMed and EMBASE databases for our systematic review from 2012 to July 15, 2021. In addition, the PSA-stratified performance of detection positivity was obtained to assess the DRs for various methods, including fluciclovine, PSMA, or choline PET/CT, with respect to biochemical recurrence based on different PSA levels.

RESULTS

In total, 64 studies involving 11,173 patients met the inclusion criteria. Of the studies, 12, 7, and 48 focused on choline, fluciclovine, and PSMA, respectively. The pooled DRs were 24%, 37%, and 44%, respectively, for a PSA level less than 0.5 ng/mL (p < 0.001); 36%, 44%, and 60% for a PSA level of 0.5-0.99 ng/mL (p < 0.001); and 50%, 61%, and 80% for a PSA level of 1.0-1.99 ng/mL (p < 0.001). The DR with 18F-labeled PSMA was higher than that with 68Ga-labeled PSMA, and the DR was 58%, 72%, and 88% for PSA levels < 0.5 ng/mL, 0.5-0.9 ng/mL, and 1.0-1.99 ng/mL, respectively.

CONCLUSION

The DRs of PSMA-radiotracers were greater than those of choline-radiotracers and fluciclovine-radiotracers at the patient level. 18F-labeled PSMA achieved a higher DR than 68Ga-labeled PSMA.

KEY POINTS

• The DRs of PSMA-radiotracers were greater than those of choline-radiotracers and fluciclovine-radiotracers at the patient level. • 18F-labeled PSMA achieved a higher DR than 68Ga-labeled PSMA.

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

Positron emission tomography (PET) incorporated with X-ray computed tomography (PET/CT) or magnetic resonance imaging (PET/MRI) is increasingly being used as a diagnostic tool for prostate cancer (PCa). In this review, we describe and evaluate the clinical performance of some Food and Drug Administration (FDA)-approved agents used for visualizing PCa: [¹⁸F]FDG, [¹¹C]choline, [¹⁸F]FACBC, [⁶⁸Ga]Ga-PSMA-11, [¹⁸F]DCFPyL, and [¹⁸F]-NaF. We carried out a comprehensive literature search based on articles published from 1 January 2010 to 1 March 2022. We selected English language articles associated with the discovery, preclinical study, clinical study, and diagnostic performance of the imaging agents for the evaluation. Prostate-specific membrane antigen (PSMA)-targeted imaging agents demonstrated superior diagnostic performance in both primary and recurrent PCa, compared with [¹¹C]choline and [¹⁸F]FACBC, both of which target dividing cells and are used especially in patients with low prostate-specific antigen (PSA) values. When compared to [¹⁸F]-NaF (which is suitable for the detection of bone metastases), PSMA-targeted agents were also capable of detecting lesions in the lymph nodes, soft tissues, and bone. However, a limitation of PSMA-targeted imaging was the heterogeneity of PSMA expression in PCa, and consequently, a combination of two PET tracers was proposed to overcome this obstacle. The preliminary studies indicated that the use of PSMA-targeted scanning is more cost efficient than conventional imaging modalities for high-risk PCa patients. Furthering the development of imaging agents that target PCa-associated receptors and molecules could improve PET-based diagnosis of PCa.

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.

18F-PSMA-11 Versus 68Ga-PSMA-11 Positron Emission Tomography/Computed Tomography for Staging and Biochemical Recurrence of Prostate Cancer: A Prospective Double-blind Randomised Cross-over Trial

BACKGROUND

Fluorine-18 (¹⁸F)-labelled prostate-specific membrane antigen (PSMA) offers several advantages over gallium-68 (⁶⁸Ga) in terms of costs, yield, transport/distribution, and image resolution.

OBJECTIVE

This trial investigates the new radiotracer ¹⁸F-PSMA-11 via a prospective, intraindividual crossover design. The trial was powered for noninferiority of ¹⁸F-PSMA-11 over ⁶⁸Ga-PSMA-11 positron emission tomography (PET)/computed tomography (CT) in terms of the number of positive PET scans. Secondary endpoints were as follows: (1) superiority of ¹⁸F-PSMA-11 over ⁶⁸Ga-PSMA-11 with respect to the number of positive PET scans, the total number of suspicious prostate cancer lesions, and the miPSMA expression score of corresponding lesions; (2) correlation of the PET/CT images with available follow-up data for ¹⁸F-PSMA-11 and ⁶⁸Ga-PSMA-11; and (3) assessment of the interobserver variability.

DESIGN, SETTING, AND PARTICIPANTS

Prostate cancer patients (primary or biochemical recurrence) were randomised in a double-blind crossover design whereby each patient received both ¹⁸F-PSMA-11 and ⁶⁸Ga-PSMA-11 PET/CT.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

All scans were reviewed and scored by three independent experienced nuclear physicians following the proposed guideline for the interpretation of PSMA-ligand PET/CT, as described by Eiber et al. RESULTS AND LIMITATIONS: In total, 82 patients were included for scan analyses. The primary endpoint was met: per patient, the proportions of positive scans rated by the three readers were 67%/67%, 65%/65%, and 73%/70% for ¹⁸F-PSMA-11/⁶⁸Ga-PSMA-11 PET/CT. The miPSMA expression score was higher for ¹⁸F-PSMA-11 than for ⁶⁸Ga-PSMA-11 for the reference reader. Follow-up data showed identical estimated sensitivity for both the ¹⁸F-PSMA-11 and the ⁶⁸Ga-PSMA-11 scan (0.92, 0.83, and 0.92 for the three readers). A fair to good agreement among readers (at patient level) was obtained, which was demonstrated by a Light's kappa value of 0.59 for both tracers.

CONCLUSIONS

The tracer ¹⁸F-PSMA-11 is noninferior to⁶⁸Ga-PSMA-11. Superiority of ¹⁸F-PSMA-11 was limited to the miPSMA expression score, given by the reference reader. Inter-rater agreement was fair to good, and equal for both radiotracers.

PATIENT SUMMARY

In this study, we compared two radiotracers: ¹⁸F-PSMA-11 and ⁶⁸Ga-PSMA-11. We proved that ¹⁸F-PSMA-11 is not inferior to ⁶⁸Ga-PSMA-11 for detecting prostate cancer and thus can be used as an alternative. Possible superiority of this tracer should be further investigated in specific subpopulations.

Pathological predictors of 18 F-DCFPyL prostate-specific membrane antigen-positive recurrence after radical prostatectomy

Objectives

To assess the correlation of pathological radical prostatectomy (RP) specimen features and prostate‐specific antigen (PSA) characteristics to imaging findings on subsequent ¹⁸F‐DCFPyL positron emission tomography/computed tomography (PET/CT) in patients with biochemical failure (BF).

Patients and Methods

Retrospective analysis of combined ¹⁸F‐DCFPyL PET/CT database of patients from centres in Australia and New Zealand was performed. A total of 205 patients presenting with BF after RP were included in this study. Imaging findings on ¹⁸F‐DCFPyL PET/CT were recorded and correlated with the PSA characteristics at BF and pathological features of the original tumour.

Results

Of the 205 patients, 120 (58.5%) had evidence of abnormal prostate‐specific membrane antigen (PSMA) expression compatible with recurrent prostate cancer. Increasing PSA velocity (P = 0.01), International Society of Urological Pathology (ISUP) Grade Group (P = 0.02), lymphovascular invasion (P = 0.05) and nodal positivity (P = 0.02) at the time of RP were more likely to demonstrate PSMA positivity. Multivariable logistic regression revealed a higher PSA level prior to PSMA PET/CT (P < 0.01), adjuvant radiotherapy (P = 0.09), Gleason score ≥8 (P < 0.01) and nodal positivity (P = 0.05) were all predictive of PSMA positivity.

Conclusion

¹⁸F‐DCFPyL PET/CT positivity, both generally and site specific, correlates with PSA and RP pathological factors. Our results echo cohorts focussing on post‐RP patients, those imaged with ⁶⁸Ga‐PSMA and those concerning biochemical persistence. Nomograms that include risk factors for ‘PSMA‐positive recurrence’ in the BF population may increase the catchment of patients with disease confined to the prostate bed or pelvis who have a greater probability of prolonged disease‐free survival.

[18F]DCFPyL PET/CT for Imaging of Prostate Cancer

Prostate-specific membrane antigen (PSMA)-directed positron emission tomography (PET) has gained increasing interest for imaging of men affected by prostate cancer (PC). In recent years, ⁶⁸Ga-labeled PSMA compounds have been widely utilized, although there is a trend towards increased utilization of ¹⁸F-labeled agents. Among others, [¹⁸F]DCFPyL (piflufolastat F 18, PYLARIFY) has been tested in multiple major trials, such as OSPREY and CONDOR, which provided robust evidence on the clinical utility of this compound for staging, restaging, and change in management. Recent explorative prospective trials have also utilized [¹⁸F]DCFPyL PET/CT for response assessment, e.g., in patients under abiraterone or enzalutamide, rendering this ¹⁸F-labeled PSMA radiotracer as an attractive biomarker for image-guided strategies in men with PC. After recent approval by the U.S. Food and Drug Administration, one may expect more widespread use, not only in the U.S., but also in Europe in the long term. In the present review, we will provide an overview of the current clinical utility of [¹⁸F]DCFPyL in various clinical settings for men with PC.

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.

Fluorine-18 Labeled Urea-Based Ligands Targeting Prostate-Specific Membrane Antigen (PSMA) with Increased Tumor and Decreased Renal Uptake

High expression of prostate-specific membrane antigen (PSMA) in prostate cancers prompted the development of the PSMA-targeted PET-imaging agent [18F]DCFPyL, which was recently approved by the FDA. Fluorine-18-labeled Lys-Urea-Glu-based oxime derivatives of [18F]DCFPyL were prepared for the comparison of their in vitro and in vivo properties to potentially improve kidney clearance and tumor targeting. The oxime radiotracers were produced by condensation of an aminooxy functionalized PSMA-inhibitor Lys-Urea-Glu scaffold with fluorine-18-labeled aldehydes. The radiochemical yields were between 15-42% (decay uncorrected) in 50-60 min. In vitro saturation and competition binding assays with human prostate cancer cells transfected with PSMA, PC3(+), indicated similar high nM binding affinities to PSMA for all radiotracers. In vivo biodistribution studies with positive control PC3(+) tumor xenografts showed that the kidneys had the highest uptake followed by tumors at 60 min. The PC3(+) tumor uptake was blocked with non-radioactive DCFPyL, and PC3(-) tumor xenograft (negative control) tumor uptake was negligible indicating that PSMA targeting was preserved. The most lipophilic tracer, [18F]2a, displayed comparable tumor-targeting to [18F]DCFPyL and a desirable alteration in pharmacokinetics and metabolism, resulting in significantly lower kidney uptake with a shift towards hepatobiliary clearance and increased liver uptake.

Synthesis, preclinical evaluation, and first-in-human study of Al18F-PSMA-Q for prostate cancer imaging

PURPOSE

To investigate the potential of a novel Al¹⁸F-labeled PSMA-targeted radiotracer for PCa diagnosis through both preclinical and pilot clinical studies.

METHODS

Al¹⁸F-PSMA-Q was prepared automatically. The binding affinity to PSMA was evaluated in vitro using the 22Rv1 (PSMA +) and PC-3 (PSMA -) cell lines. Pharmacokinetics evaluation, biodistribution study, Micro-PET imaging of Al¹⁸F-PSMA-Q in normal mice and tumor-bearing mice, and a comparison with ¹⁸F-DCFPyL were performed. PET/CT imaging was performed on 8 healthy volunteers and 20 newly diagnosed PCa patients at 1 h post-injection (p.i.). The biodistribution in human and preliminary diagnostic efficacy of Al¹⁸F-PSMA-Q were evaluated, and the radiation dosimetry was estimated using OLINDA/EXM 2.0 software.

RESULT

Qualified Al¹⁸F-PSMA-Q was efficiently prepared with a non-decay-corrected radiochemical yield (RCY) of 22.0-28.3%, a specific activity (SA) of > 50 GBq/μmol. The hydrophilicity was comparably high with a log P value of - 3.69 ± 0.39. Al¹⁸F-PSMA-Q was found to bind to PSMA specifically with a Ki value of 17.05 ± 1.14 nM. The distribution and elimination half-lives of Al¹⁸F-PSMA-Q were 3.93 min and 14.22 min, respectively, which were shorter than those of ¹⁸F-DCFPyL. Micro-PET imaging of Al¹⁸F-PSMA-Q can clearly differentiate 22Rv1 tumors from PC-3 tumors and background with a high SUVmax of 2.17 ± 0.42 and a tumor-to-muscle ratio of 84.37 ± 31.62, which were higher than those of ¹⁸F-DCFPyL (1.79 ± 0.39 and 13.25 ± 1.65). The uptake of Al¹⁸F-PSMA-Q in 22Rv1 cells and tumors can be substantially blocked by 2-PMPA. High level accumulation of Al¹⁸F-PSMA-Q was observed in organs physiologically expressing PSMA. Twenty-six tumor lesions were detected in 20 PCa patients, and the mean SUVmax values of primary tumors, lymph node metastasis, bone metastases, and tumor-muscle ratios were 19.71 ± 16.52, 5.11, 31.30 ± 29.85, and 44.77 ± 22.29, respectively. The mean SUVmax of tumors in patients with PSA > 10 ng/mL was significantly higher than that in patients with PSA ≤ 10 ng/mL (25.97 ± 18.64 vs. 10.33 ± 3.74). Meanwhile, the mean SUVmax of tumors in patients with a Gleason score ≥ 8 was significantly higher than that in patients with a Gleason score < 8 (31.85 ± 22.09 vs. 13.18 ± 11.58). The kidneys received the highest estimated dose of 0.098 ± 0.006 mGy/MBq, and the effective dose was calculated as 0.0128 ± 0.007 mGy/MBq.

CONCLUSION

The novel qualified PSMA-targeted radiotracer Al¹⁸F-PSMA-Q was conveniently prepared with favorable yield and SA. The results of preclinical and pilot clinical studies exhibited a high specific uptake in PCa lesions and an excellent tumor-to-background ratio with a reasonable radiation exposure, which indicated the great potential of Al¹⁸F-PSMA-Q for PCa imaging.

TRIAL REGISTRATION

Chinese Clinical trial registry ChiCTR2100053507, Registered 23 November 2021, retrospectively registered.

Oligometastatic disease in biochemical recurrence of prostate cancer: Prevalence on PSMA PET/CT and consecutive metastasis-directed therapy - Experience at a tertiary referral center

AIM

The aim of our study was to address the prevalence of oligometastatic recurrent prostate cancer (PCa) on PSMA-PET and the associated practice of metastasis-directed therapy (MDT). Next, we aimed to determine a PSA threshold below which most patients had local and/or oligometastatic recurrence on PSMA-PET.

METHODS

One hundred and ten consecutive patients with biochemical recurrence (BCR) after radical prostatectomy (RP) ± radiation were referred for ⁶⁸Ga-PSMA-11 or ¹⁸F-DCFPyL PET/CT. We correlated the location and number of PSMA-positive lesions against the treatment choice after imaging. Detection rates were stratified by PSA levels at the time of PET/CT. The study design was monocentric retrospective.

RESULTS

Thirty-four patients (30.9%) had a PSMA-negative scan, while 17 (15.5%) had local recurrence and 59 (53.6%) had metastatic recurrence on PSMA-PET. ROC analysis revealed a cut-off of ≤3 metastatic lesions on PSMA-PET for the steering of treatment decisions towards MDT rather than solely systemic therapy (AUC: 0.88). Defined as 3 or fewer metastatic lesions, oligometastatic recurrent PCa was found in up to 30% (33/110) of all patients. At PSA levels below 3.5 ng/ml, the rate of PSMA-positive disease that was locally confined or oligometastatic was 76% (45/59), dropping significantly to 29.4% (5/17) above this threshold (p<0.001) as polymetastatic findings became more frequent.

CONCLUSION

The detection of ≤3 oligometastases on PSMA-PET encouraged the consecutive pursuit of MDT instead of systemic therapy alone. PSMA-PET predominantly captured patients at recurrence stages amenable to localized treatment when initiated at PSA levels below 3.5 ng/ml.

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.

PSMA-Targeting Imaging and Theranostic Agents-Current Status and Future Perspective

In the past two decades, extensive efforts have been made to develop agents targeting prostate-specific membrane antigen (PSMA) for prostate cancer imaging and therapy. To date, represented by two recent approvals of [⁶⁸Ga]Ga-PSMA-11 and [¹⁸F]F-DCFPyL by the United States Food and Drug Administration (US-FDA) for positron emission tomography (PET) imaging to identify suspected metastases or recurrence in patients with prostate cancer, PSMA-targeting imaging and theranostic agents derived from small molecule PSMA inhibitors have advanced to clinical practice and trials of prostate cancer. The focus of current development of new PSMA-targeting agents has thus shifted to the improvement of in vivo pharmacokinetics and higher specific binding affinity with the aims to further increase the detection sensitivity and specificity and minimize the toxicity to non-target tissues, particularly the kidneys. The main strategies involve systematic chemical modifications of the linkage between the targeting moiety and imaging/therapy payloads. In addition to a summary of the development history of PSMA-targeting agents, this review provides an overview of current advances and future promise of PSMA-targeted imaging and theranostics with focuses on the structural determinants of the chemical modification towards the next generation of PSMA-targeting agents.

Patterns of Prostate Cancer Recurrence After Brachytherapy Determined by Prostate-Specific Membrane Antigen-Positron Emission Tomography and Computed Tomography Imaging

PURPOSE

The aim of this study was to characterize the patterns of prostate cancer recurrence after brachytherapy (BT) using 2-(3-[1-carboxy-5-([6-¹⁸F-fluoropyridine-3-carbonyl]-amino)-pentyl]-ureido)-pentanedioic acid ([¹⁸F]DCFPyL) prostate-specific membrane antigen (PSMA) positron emission tomography (PET) and computed tomography (CT) imaging.

METHODS AND MATERIALS

Patients were selected from an ongoing prospective institutional trial investigating the use of [¹⁸F]DCFPyL PSMA PET and CT in recurrent prostate cancer (NCT02899312). This report included patients who underwent BT (either monotherapy or boost) and experienced a biochemical failure (BF) defined by the Phoenix definition (prostate-specific antigen [PSA] > 2 ng/mL above nadir).

RESULTS

Between March 2017 and April 2020, 670 patients underwent [¹⁸F]DCFPyL PSMA PET and CT imaging. Of these 670 patients, 93 were treated with BT; 73 underwent monotherapy, and 20 underwent BT boost (19 low-dose rate and 1 high-dose rate). To report on patterns of recurrence outcomes, 86 patients (median prescan PSA 6.0) with a positive [¹⁸F]DCFPyL PSMA PET and CT scan and true BF were included. The most common location of relapse was local; 62.8% had a component of local failure (defined as prostate and/or seminal vesicles), and 46.5% had isolated local failure only, with no other sites of involvement. Regional failure occurred in 40.7% of patients, and 36.0% had metastatic failure. Isolated local recurrence was seen in 54.3% of monotherapy patients versus only in 12.5% of boost patients. Metastatic failure was seen in 28.6% of monotherapy patients versus 68.8% of the boost patients. Local recurrences (69.0%) were found within the same prostate biopsy sextant involved with the tumor at diagnosis, and 76.0% of patients with seminal vesicle recurrences had prostate-base involvement at diagnosis.

CONCLUSIONS

Contrary to previous evidence, our study suggests that in prostate BT patients with biochemical recurrence, the most common site of failure is local for the patients treated with monotherapy and metastatic for patients treated with a combination of external beam radiation and BT boost.

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.

Diagnostic performance and clinical impact of 68Ga-PSMA-11 imaging in early relapsed prostate cancer after radical therapy: a prospective multicenter study (IAEA-PSMA study)

Biochemical recurrence (BCR) is a clinical challenge in prostate cancer (PCa) patients, as recurrence localization guides subsequent therapies. The use of PET with prostate-specific membrane antigen (PSMA) provides better accuracy than conventional imaging practice. This prospective, multicenter, international study was performed to evaluate the diagnostic performance and clinical impact of PSMA PET/CT for evaluating BCR in PCa patients in a worldwide scenario. Methods: Patients were recruited from 17 centers in 15 countries. Inclusion criteria were histopathologically proven prostate adenocarcinoma, previous primary treatment, clinically established BCR, and negative conventional imaging (CT plus bone scintigraphy) and MRI results for patients with PSA levels of 4–10 ng/mL. All patients underwent PET/CT scanning with ⁶⁸Ga-PSMA-11. Images and data were centrally reviewed. Multivariate logistic regression analysis was applied to identify the independent predictors of PSMA-positive results. Variables were selected for this regression model on the basis of significant associations in the univariate analysis and previous clinical knowledge: Gleason score, the PSA level at the time of the PET scan, PSA doubling time, and primary treatment strategy. All patients were monitored for a minimum of 6 mo. Results: From a total of 1,004 patients, 77.7% were treated initially with radical prostatectomy and 22.3% were treated with radiotherapy. Overall, 65.1% had positive PSMA PET/CT results. PSMA PET/CT positivity was correlated with the Gleason score, PSA level at the time of the PET scan, PSA doubling time, and radiotherapy as the primary treatment (P < 0.001). Treatment was modified on the basis of PSMA PET/CT results in 56.8% of patients. PSMA PET/CT positivity rates were consistent and not statistically different among countries with different incomes. Conclusion: This multicenter, international, prospective trial of PSMA PET/CT confirmed its capability for detecting local and metastatic recurrence in most PCa patients in the setting of BCR. PSMA PET/CT positivity was correlated with the Gleason score, PSA level at the time of the PET scan, PSA doubling time, and radiotherapy as the primary treatment. PSMA PET/CT results led to changes in therapeutic management in more than half of the cohort. The study demonstrated the reliability and worldwide feasibility of PSMA PET/CT in the workup of PCa patients with BCR.

[18F]DCFPyL PET/CT in detection and localization of recurrent prostate cancer following prostatectomy including low PSA < 0.5 ng/mL

PURPOSE

The primary aim of this retrospective multicenter analysis was to assess the performance of PSMA PET/CT using [18F]DCFPyL in the detection and localization of recurrent prostate cancer post radical prostatectomy (RP). Particular reference is given to low PSA groups < 0.5 ng/mL to aid discussion around the inclusion of this group in PSMA guidelines and funding pathways.

METHODS

Retrospective analysis of combined PSMA database patients from centers in Australia and New Zealand. Two hundred twenty-two patients presenting with recurrence post RP were stratified into five PSA groups (ng/mL): 0-0.19, 0.2-0.49, 0.5-0.99, 1-1.99, and ≥ 2. Lesions detected by [18F]DCFPyL PET/CT were recorded as local recurrence, locoregional nodes, and metastases.

RESULTS

Of 222 patients, 155 (69.8%) had evidence of abnormal uptake suggestive of recurrent prostate cancer. The detection efficacies for [18F]DCFPyL PET/CT were 91.7% (44/48) for PSA levels ≥ 2 ng/mL, 82.1% (23/28) for PSA levels 1-1.99 ng/mL, 62.8% (27/43) for PSA levels 0.5-0.99 ng/mL, 58.7% (54/92) for PSA levels 0.2-0.49 ng/mL, and 63.6% (7/11) for PSA levels ≤ 0.2 ng/mL. In those with PSA < 0.5 ng/mL, 47.6% (49/103) had detectable lesions, 71.4% (35/49) had disease confined to the pelvis, 22.4% (11/49) had prostate bed recurrence, 49.0% (24/49) had pelvic lymph nodes, and 28.6% (14/49) had extra pelvic disease.

CONCLUSION

[18F]DCFPyL PET/CT has a high detection rate in recurrence following RP even at low PSA levels with similar detection levels in the PSA subgroups < 0.5 ng/mL. Employing rigid PSA thresholds when constructing guidelines for PSMA PET/CT funding eligibility may result in a significant number of patients below such thresholds having delayed or inappropriate treatment.

Performance of 18F-DCFPyL PET/CT Imaging in Early Detection of Biochemically Recurrent Prostate Cancer: A Systematic Review and Meta-Analysis

Background: Prostate-specific membrane antigen (PSMA)-targeted 2-(3-{1-carboxy-5-[(6-[18F] fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (18F-DCFPyL) positron emission tomography/computed tomography (PET/CT) has shown advantages in primary staging, restaging, and metastasis detection of prostate cancer (PCa). However, little is known about the role of 18F-DCFPyL PET/CT in biochemically recurrent prostate cancer (BRPCa). Hence, we performed a systematic review and meta-analysis to evaluate 18F-DCFPyL PET/CT as first-line imaging modality in early detection of BRPCa. Methods: A comprehensive literature search of PubMed, Web of Science, Embase, and Cochrane Library was conducted until December 2020. The pooled detection rate on a per-person basis and together with 95% confidence interval (CI) was calculated. Furthermore, a prostate-specific antigen (PSA)-stratified performance of detection positivity was obtained to assess the sensitivity of 18F-DCFPyL PET/CT in BRPCa with different PSA levels. Results: A total of nine eligible studies (844 patients) were included in this meta-analysis. The pooled detection rate (DR) of 18F-DCFPyL PET/CT in BRPCa was 81% (95% CI: 76.9-85.1%). The pooled DR was 88.8% for PSA ≥ 0.5 ng/ml (95% CI: 86.2-91.3%) and 47.2% for PSA < 0.5 ng/ml (95% CI: 32.6-61.8%). We also noticed that the regional lymph node was the most common site with local recurrence compared with other sites (45.8%, 95% CI: 42.1-49.6%). Statistical heterogeneity and publication bias were found. Conclusion: The results suggest that 18F-DCFPyL PET/CT has a relatively high detection rate in BRPCa. The results also indicate that imaging with 18F-DCFPyL may exhibit improved sensitivity in BRPCa with increased PSA levels. Considering the publication bias, further large-scale multicenter studies are warranted for validation.