Impact of 68Ga-PSMA-11 PET on Management in Patients with Biochemically Recurrent Prostate Cancer

Detection rate of gastrin-releasing peptide receptor (GRPr) targeted tracers for positron emission tomography (PET) imaging in primary prostate cancer: a systematic review and meta-analysis

The gastrin-releasing peptide receptor (GRPr) has gained recognition as a promising target for both diagnostic and therapeutic applications in a variety of human cancers. This study aims to explore the primary tumor detection capabilities of [68Ga] Ga-GRPr PET imaging, specifically in newly diagnosed intra-prostatic prostate cancer lesions (PCa). Following PRISMA-DTA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses of Diagnostic Test Accuracy Studies) guidelines, a systematic literature search was conducted using the Medline, Embase, Scopus, and Web of Science databases. Data regarding patient characteristics and imaging procedure details-including the type of radiotracer used, administered activity, image acquisition time, scanner modality, criteria, and detection rate of index test-were extracted from the included studies. The pooled patient-and lesion-based detection rates, along with their corresponding 95% confidence intervals (CI), were calculated using a random effects model. The final analysis included 9 studies involving 291 patients and 350 intra-prostatic lesions with [68Ga] Ga-GRPr PET imaging in primary PCa. In per-patient-based analysis of [68Ga] Ga-GRPr PET imaging, the pooled detection rates of overall and patients with Gleason score ≥ 7 were 87.09% (95% CI 74.98-93.82) and 89.01% (95% CI 68.17-96.84), respectively. In per-lesion-based analysis, the pooled detection rate [68Ga] Ga-GRPr PET imaging was 78.54% (95% CI 69.8-85.29). The pooled detection rate mpMRI (multiparametric magnetic resonance imaging) in patient-based analysis was 91.85% (95% CI 80.12-96.92). The difference between the detection rates of the mpMRI and [68Ga] Ga-GRPr PET imaging was not statistically significant (OR 0.90, 95% CI 0.23-3.51). Our findings suggest that [68Ga] Ga-GRPr PET imaging has the potential as a diagnostic target for primary PCa. Future research is needed to determine the effectiveness of [68Ga] Ga-GRPr PET in delivering additional imaging data and guiding therapeutic decisions.

Long-Term Outcomes of Prostate-Specific Membrane Antigen-PET Imaging of Recurrent Prostate Cancer

Importance

Although prostate-specific membrane antigen positron emission tomography (PSMA-PET) has shown improved sensitivity and specificity compared with conventional imaging for the detection of biochemical recurrent (BCR) prostate cancer, the long-term outcomes of a widespread shift in imaging are unknown.

Objective

To estimate long-term outcomes of integrating PSMA-PET into the staging pathway for recurrent prostate cancer.

Design, Setting, and Participants

This decision analytic modeling study simulated outcomes for patients with BCR following initial definitive local therapy. Inputs used were from the literature and a retrospective cohort study conducted at 2 institutions. The base case analysis assumed modest benefits of earlier detection and treatment, and scenario analyses considered prostate-specific antigen (PSA) level at imaging and different outcomes of earlier vs delayed treatment. The analysis was performed between April 1, 2023, and May 1, 2024.

Exposures

(1) Immediate PSMA-PET imaging, (2) conventional imaging (computed tomography and bone scan [CTBS]) followed by PSMA-PET if CTBS findings were negative or equivocal, and (3) CTBS alone.

Main Outcomes and Measures

The main outcomes were detection of metastases, deaths from prostate cancer, and life-years and quality-adjusted life-years (QALYs) gained.

Results

The model estimated that per 1000 simulated patients with BCR (assumed median age, 66 years), PSMA-PET is expected to diagnose 611 (95% uncertainty interval [UI], 565-656) patients with metastasis compared with 630 (95% UI, 586-675) patients diagnosed using CTBS followed by PSMA-PET and 297 (95% UI, 202-410) patients diagnosed using CTBS alone. Moreover, the estimated number of prostate cancer deaths was 512 (95% UI, 472-552 deaths) with PSMA-PET, 520 (95% UI, 480-559 deaths) with CTBS followed by PSMA-PET, and 587 (95% UI, 538-632 deaths) with CTBS alone. Imaging with PSMA-PET yielded the highest number of QALYs, which were 824 (95% UI, 698-885) higher than CTBS. These results differed by PSA level at the time of testing, with the highest incremental life-years and QALYs and lowest number of deaths from prostate cancer among patients with PSA levels of at least 5.0 ng/mL. Finally, the estimates were sensitive to the expected benefit of initiating therapy for recurrent prostate cancer earlier in the disease course.

Conclusions and Relevance

The results of this decision-analytic model suggest that upfront PSMA-PET imaging for the evaluation of BCR is expected to be associated with reduced cancer mortality and gains in life-years and QALYs compared with the conventional imaging strategy, assuming modest benefits of earlier detection and treatment.

Utility of 64Cu-Sarcophagine-Bombesin PET/CT in Men with Biochemically Recurrent Prostate Cancer and Negative or Equivocal Findings on 68Ga-PSMA-11 PET/CT

Despite a high detection rate of 68Ga-prostate-specific membrane antigen (PSMA) PET/CT in biochemical recurrence (BCR) of prostate cancer, a significant proportion of men have negative 68Ga-PSMA-11 PET/CT results. Gastrin-releasing peptide receptor, targeted by the copper-chelated bombesin analog 64Cu-sarcophagine-bombesin (SAR-BBN) PET/CT, is also overexpressed in prostate cancer. In this prospective imaging study, we investigate the detection rate of 64Cu-SAR-BBN PET/CT in patients with BCR and negative or equivocal 68Ga-PSMA-11 PET/CT results. Methods: Men with confirmed adenocarcinoma of the prostate, prior definitive therapy, and BCR (defined as a prostate-specific antigen [PSA] level > 0.2 ng/mL) with negative or equivocal 68Ga-PSMA-11 PET/CT results within 3 mo were eligible for enrollment. 64Cu-SAR-BBN PET/CT scans were acquired at 1 and 3 h after administration of 200 MBq of 64Cu-SAR-BBN, with further delayed imaging undertaken optionally at 24 h. PSA (ng/mL) was determined at baseline. All PET (PSMA and bombesin) scans were assessed visually. Images were read with masking of the clinical results by 2 experienced nuclear medicine specialists, with a third reader in cases of discordance. Accuracy was defined using a standard of truth that included biopsy confirmation, confirmatory imaging, or response to targeted treatment. Results: Twenty-five patients were enrolled. Prior definitive therapy was radical prostatectomy (n = 24, 96%) or radiotherapy (n = 1, 4%). The median time since definitive therapy was 7 y (interquartile range [IQR], 4-11 y), and the Gleason score was 7 or less (n = 15, 60%), 8 (n = 3, 12%), or 9 (n = 7, 28%). The median PSA was 0.69 ng/mL (IQR, 0.28-2.45 ng/mL). Baseline PSMA PET scans were negative in 19 patients (76%) and equivocal in 6 (24%). 64Cu-SAR-BBN PET-avid disease was identified in 44% (11/25): 12% (3/25) with local recurrence, 20% (5/25) with pelvic node metastases, and 12% (3/25) with distant metastases. The κ-score between readers was 0.49 (95% CI, 0.16-0.82). Patients were followed up for a median of 10 mo (IQR, 9-12 mo). Bombesin PET/CT results were true-positive in 5 of 25 patients (20%), false-positive in 2 of 25 (8%), false-negative in 7 of 25 (28%), and unverified in 11 of 25 (44%). Conclusion: 64Cu-SAR-BBN PET/CT demonstrated sites of disease recurrence in 44% of BCR cases with negative or equivocal 68Ga-PSMA-11 PET/CT results. Further evaluation to confirm diagnostic benefit is warranted.

Dual-time-point dynamic 68Ga-PSMA-11 PET/CT for parametric imaging generation in prostate cancer

PURPOSE

To investigate the optimal dual-time-point (DTP) approaches using dynamic 68Ga-PSMA-11 PET/CT imaging to generate parametric images for prostate cancer patients.

METHODS

Fifteen patients with prostate cancer were intravenously administered 68Ga-PSMA-11 of 181.9 ± 47.2 MBq, followed by an immediate 60 min dynamic PET/CT scan. List-mode data were reconstructed into 25 timeframes (6 × 10 s, 8 × 30 s, and 11 × 300 s) and corrected for motion and partial volume effect. DTP parametric images were generated using different interval time points of 5 min and 10 min, with a minimum of 30 min time interval. Net influx rates (Ki) were calculated through the fitting of a single irreversible two-tissue compartmental model. Intraclass correlation coefficient (ICC) values between DTP protocols and 60 min Ki were obtained. Lesion-to-background ratios (LBRs) of Ki and standardized uptake value (SUV) images in each DTP protocol were determined.

RESULTS

The DTP protocol of 5-10 min with a 40-45 min interval showed the highest ICC of 0.988 compared with the 60 min Ki, whereas the ICC values for the intervals of 0-5 min with 55-60 min and 0-10 min with 50-60 min were 0.941. The LBRs of the 60 min Ki, 5-10 min with 40-45 min Ki, 0-5 min with 55-60 min Ki, 0-10 min with 50-60 min Ki, SUVmean, and SUVmax images were 29.53 ± 27.33, 13.05 ± 15.28, 45.15 ± 53.11, 45.52 ± 70.31, 19.77 ± 23.43, and 25.06 ± 30.07, respectively.

CONCLUSION

The 0-5 min with 55-60 min DTP parametric imaging exhibits a comparable Ki to 60 min parametric imaging and remarkable image quality and contrast than SUV imaging, enhancing prostate cancer diagnosis while maintaining time efficiency.

Impact of Clinical Factors on 18F-Flotufolastat Detection Rates in Men With Recurrent Prostate Cancer: Exploratory Analysis of the Phase 3 SPOTLIGHT Study

Purpose

18F-Flotufolastat (18F-rhPSMA-7.3) is a newly approved prostate-specific membrane antigen targeting radiopharmaceutical for diagnostic imaging of prostate cancer (PCa). SPOTLIGHT (National Clinical Trials 04186845) evaluated 18F-flotufolastat in men with suspected PCa recurrence. Here, we present results of predefined exploratory endpoints from SPOTLIGHT to evaluate the impact of clinical factors on 18F-flotufolastat detection rates (DR).

Methods and Materials

The impact of baseline prostate-specific antigen (PSA), PSA doubling time (PSAdt), and International Society of Urologic Pathology Grade Group (GG) on 18F-flotufolastat DR was evaluated among all SPOTLIGHT patients with an evaluable scan, with DR stratified according to the patients' prior treatment (radical prostatectomy ± radiation therapy [RP] or radiation therapy only [RT]). The patients underwent positron emission tomography 50 to 70 minutes after receiving 18F-flotufolastat (296 MBq IV), and scans were read by 3 blinded central readers, with the majority read representing agreement between ≥2 readers.

Results

In total, 389 men (median PSA: 1.10 ng/mL) were evaluable. By majority read, 18F-flotufolastat identified distant lesions in 39% and 43% of patients treated with prior RP or RT, respectively. The overall DR broadly increased with increasing PSA (<0.2 ng/mL: 33%; ≥10 ng/mL: 100%). Among patients with PSA <1 ng/mL, 68% had positive scans, and 27% had extrapelvic findings. PSAdt was available for 145/389 (37%) patients. PSAdt did not appear to influence 18F-flotufolastat DR (77%-90% across all PSAdt categories). Among patients with prior RP, DR ranged from 70% to 83% across PSAdt categories, and 100% DR was reported for all post-RT patients. In total, 362/389 (93%) patients had baseline GG data. Overall DRs were uniformly high (75%‒95%) across all GG. When stratified by prior treatment, DRs across all GG were 69% to 89% in patients with prior RP and ≥96% in patients with prior RT.

Conclusions

18F-Flotufolastat-positron emission tomography enabled the accurate detection of recurrent PCa lesions across a wide range of PSA, PSAdt, and International Society of Urologic Pathology GG, thus supporting its clinical utility for a broad range of patients with recurrent PCa.

Evaluating appropriateness of 18F-fluciclovine PET/CT relative to standard of care imaging guidelines and the impact of ADT on positivity: a prospective study in 62 Veterans Administration patients at a single institution

BACKGROUND

According to the National Comprehensive Cancer Network Guidelines, 18F-fluciclovine PET/CT is considered appropriate after negative standard of care (SOC) imaging.

OBJECTIVE

To prospectively compare 18F-fluciclovine to SOC imaging, investigate whether it should be done when SOC imaging is (+), and evaluate its detection rate in patients receiving androgen deprivation therapy.

METHODS

We recruited 57 prostate cancer patients with biochemical recurrence with 18F-fluciclovine PET/CT and SOC imaging within 30 days. Prostate-specific antigen (PSA) level, Gleason score (GS), history of radical prostatectomy (RP), radiation therapy (RT) or hormone therapy (HT) were reviewed.

RESULTS

The 57 patients had a median PSA of 2.6 and average GS of 7.4; 27 (47.4%) had RP, 28 (49.1%) had RT, 1 (1.75%) had HT and 1 (1.75%) observation only. 18F-fluciclovine identified disease recurrence in 45/57 patients (78.9%), including oligometastasis in 18/45 (40%). SOC imaging identified recurrent disease in 12/57 patients (21.1%) while 18F-fluciclvoine identified additional sites of disease in 11/12 (91.7%). The (+) 18F-fluciclovine studies had a median PSA 2.6 ng/ml compared to 6.0 ng/ml in the (+) SOC studies.

CONCLUSION

18F-fluciclovine was superior to SOC imaging for lesion detection, identification of oligometastasis and identification of additional sites of disease.

A prospective study on the early evaluation of response to androgen receptor-targeted agents with 11C-Choline, 68Ga-PSMA, and 18F-FACBC PET in metastatic castration-resistant prostate cancer: a single-center experience

BACKGROUND

The early identification of responsive and resistant patients to androgen receptor-targeting agents (ARTA) in metastatic castration-resistant prostate cancer (mCRPC) is not completely possible with prostate-specific antigen (PSA) assessment and conventional imaging. Considering its ability to determine metabolic activity of lesions, positron emission tomography (PET) assessment might be a promising tool.

PATIENTS AND METHODS

We carried out a monocentric prospective study in patients with mCRPC treated with ARTA to evaluate the role of different PET radiotracers: 49 patients were randomized to receive 11C-Choline, Fluorine 18 fluciclovine (anti-1-amino-3-18F-fluorocyclobutane-1-carboxylic acid - FACBC) (18F-FACBC), or Gallium-68-prostate-specific-membrane-antigen (68Ga-PSMA) PET, one scan before therapy and one 2 months later. The primary aim was to investigate the performance of three novel PET radiotracers for the early evaluation of response to ARTA in metastatic CRPC patients; the outcome evaluated was biochemical response (PSA reduction ≥50%). The secondary aim was to investigate the prognostic role of several semiquantitative PET parameters and their variations with the different radiotracers in terms of biochemical progression-free survival (bPFS) and overall survival (OS). The study was promoted by the Italian Department of Health (code RF-2016-02364809).

RESULTS

Regarding the primary endpoint, at log-rank test a statistically significant correlation was found between metabolic tumor volume (MTV) (P = 0.018) and total lesion activity (TLA) (P = 0.025) percentage variation among the two scans with 68Ga-PSMA PET and biochemical response. As for the secondary endpoints, significant correlations with bPFS were found for 68Ga-PSMA total MTV and TLA at the first scan (P = 0.001 and P = 0.025, respectively), and MTV percentage variation (P = 0.031). For OS, statistically significant correlations were found for different 68Ga-PSMA and 18F-FACBC parameters and for major maximum standardized uptake value at the first 11C-Choline PET scan.

CONCLUSIONS

Our study highlighted that 11C-Choline, 68Ga-PSMA, and 18F-FACBC semiquantitative PET parameters and their variations present a prognostic value in terms of OS and bPFS, and MTV and TLA variations with 68Ga-PSMA PET a correlation with biochemical response, which could help to assess the response to ARTA.

Detection Rate of PSMA PET Using Different Ligands in Men with Biochemical Recurrent Prostate Cancer Following Radical Treatment: A Systematic Review and Meta-analysis of Prospective Studies

BACKGROUND

Despite the acknowledged diagnostic detection rate of prostate-specific membrane antigen (PSMA) positron emission tomography (PET) imaging in prostate cancer, little is known about the quality of evidence, particularly focusing on prospective studies. Most systematic reviews are based on retrospective reports.

RATIONALE AND OBJECTIVES

To conduct systematic review and meta-analysis of prospective studies reporting the diagnostic detection rate of PSMA PET (computed tomography (CT) and MR) for the detection of biochemically recurrent metastatic prostate cancer.

MATERIALS AND METHODS

We systematically searched PubMed, MEDLINE, Embase, and Scopus, from database until March 1, 2023 for randomized controlled trials and prospective studies using PSMA PET imaging in prostate cancer. The primary endpoint was to assess diagnostic detection rate of PSMA PET imaging in the detection of recurrent prostate cancer in men with biochemical relapse following radical treatment. We calculated the pooled overall diagnostic detection rate with 95% CI using a random-effects model and assessed the heterogeneity between the studies including risk of biases estimation.

RESULTS

A total of 6800 patients from 32 articles were included in this study. The overall detection rate of PSMA PET for prostate cancer was 0.67 (95% CI, 0.63, 0.71). For histologically confirmed lymph nodes, the PPV from 13 prospective studies containing 1496 patients was 0.96 (95% CI, 0.93, 0.99). We performed a subgroup analysis of PSMA PET detection rates according to categorically grouped Prostate Specific Antigen (PSA) values of 0-0.5, 0.5-1.0, 1.0-2.0, and >2.0 ng/ml and obtained detection rates of 0.44, 0.63, 0.82, and 0.94, respectively. The detection rate of 18F PSMA was better in men with a PSA between 1 ng/ml and 2 ng/ml in comparison to 68Ga PSMA (0.91 with 95% CI 0.81-0.99 vs. 0.79 with 95% CI 0.73, 0.85).

CONCLUSION

PSMA PET imaging provides a good detection rate for the metastatic recurrence of prostate cancer in men with biochemical relapse following radical treatment. The detection rate improves significantly above a serum PSA value of 1 ng/ml. The diagnostic detection rate of 18F-PSMA is best at PSA values between 1 and 2 ng/ml, in comparison to 68Ga PSMA. This conclusion is heavily biased, further research needs to focus on better methodology to minimize the risk of biases.

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.

Prostate-Specific Membrane Antigen: Gateway to Management of Advanced Prostate Cancer

Prostate-specific membrane antigen (PSMA) as a transmembrane protein is overexpressed by prostate cancer (PC) cells and is accessible for binding antibodies or low-molecular-weight radioligands due to its extracellular portion. Successful targeting of PSMA began with the development of humanized J591 antibody. Due to their faster clearance compared to antibodies, small-molecule radioligands for targeted imaging and therapy of PC have been favored in recent development efforts. PSMA positron emission tomography (PET) imaging has higher diagnostic performance than conventional imaging for initial staging of high-risk PC and biochemical recurrence detection/localization. However, it remains to be demonstrated how to integrate PSMA PET imaging for therapy response assessment and as an outcome endpoint measure in clinical trials. With the recent approval of 177Lu-PSMA-617 by the US Food and Drug Administration for metastatic castration-resistant PC progressing after chemotherapy, the high value of PSMA-targeted therapy was confirmed. Compared to standard of care, PSMA-based radioligand therapy led to a better outcome and a higher quality of life. This review, focusing on the advanced PC setting, provides an overview of different approved and nonapproved PSMA-targeted imaging and therapeutic modalities and discusses the future of PSMA-targeted theranostics, also with an outlook on non-radiopharmaceutical-based PSMA-targeted therapies.

Medicinal (Radio) Chemistry: Building Radiopharmaceuticals for the Future

Radiopharmaceuticals are increasingly playing a leading role in diagnosing, monitoring, and treating disease. In comparison with conventional pharmaceuticals, the development of radiopharmaceuticals does follow the principles of medicinal chemistry in the context of imaging-altered physiological processes. The design of a novel radiopharmaceutical has several steps similar to conventional drug discovery and some particularity. In the present work, we revisited the insights of medicinal chemistry in the current radiopharmaceutical development giving examples in oncology, neurology, and cardiology. In this regard, we overviewed the literature on radiopharmaceutical development to study overexpressed targets such as prostate-specific membrane antigen and fibroblast activation protein in cancer; β-amyloid plaques and tau protein in brain disorders; and angiotensin II type 1 receptor in cardiac disease. The work addresses concepts in the field of radiopharmacy with a special focus on the potential use of radiopharmaceuticals for nuclear imaging and theranostics.

A Clinical Role of PET-MRI in Prostate Cancer?

PET/MRI is a relevant application field for prostate cancer management, offering advantages in early diagnosis, staging, and therapy planning. Despite drawbacks such as higher costs, longer acquisition time, and the need for skilled personnel, the technical integration of PET and MRI provides valuable information for detecting primary tumors, identifying metastases, and characterizing the disease, leading to more accurate staging and personalized treatment strategies. However, PET/MRI adoption has been slow, but ongoing technological advancements and AI integration might overcome challenges and improve clinical utility. As precision medicine gains importance in oncology, PET/MRI's multiparametric data can tailor treatment plans to individual patients, providing a comprehensive assessment of tumor biology and aggressiveness for more effective therapeutic strategies.

PSMA PET imaging in the diagnosis and management of prostate cancer

Prostate cancer is the second leading cause of cancer-related deaths in men in the United States. Imaging techniques such as CT, MRI, and bone scans have traditionally been used for diagnosis and staging. Molecular imaging modalities targeting the prostate-specific membrane antigen (PSMA) have recently gained attention due to their high affinity and accuracy. PSMA PET has been combined with other modalities such as multiparametric MRI for better diagnostic and prognostic performance. PSMA imaging has been studied at different clinical settings with a wide range of disease aggressiveness. In this review we will explore the role of PSMA PET in high-risk prostate cancer staging, biochemical recurrence, and castration-resistant prostate cancer. The primary focus of this review article is to examine the latest developments in the use of PSMA imaging and emphasize the clinical situations where its effectiveness has been demonstrated to significantly impact the treatment of prostate cancer. In addition, we will touch upon the potential future advancements of PSMA PET imaging and its evolving significance in the management of prostate cancer.

Effectiveness of shielding materials against 177Lu gamma rays and the corresponding distance relationship

OBJECTIVE

The purpose of this study is to determine the dose reduction of different shielding materials at various distances from a 177Lu photon radiation source.

METHODS

Two protective aprons with lead equivalent thicknesses of 0.25 mm and 0.35 mm and tungsten-containing rubber (TCR) were used as shielding materials. A vial containing 177Lu was sealed in a lead container so that a narrow beam went out through a 3 mm-diameter hole. The dose rate was measured at distances of 0, 10, 50, 100, and 200 cm from the source using a NaI scintillation survey meter to obtain the rate of dose reduction. TCR was tested with thicknesses ranging from 0.3 to 1.0 mm at 0.1 mm intervals and from 1.0 to 4.0 mm at 0.5 mm intervals.

RESULTS

At distances of 0, 10, 50, 100, and 200 cm, the dose reduction for the lead equivalent thickness of 0.25 mm were 32.7%, 54.5%, 93.1%, 97.9%, and 99.6%, respectively; and for the lead equivalent thickness of 0.35 mm were 53.4%, 70.6%, 95.6%, 98.9%, and 99.6%, respectively. Without any shielding, the dose rate decreased by 34.4% at 10 cm and by 88.8% at 50 cm from the radiation source. The dose reduction for the TCR thickness of 3.5 mm was 89.8% at 0 cm and 93.3% at 10 cm. The TCR thickness of 0.4 mm provided a dose reduction comparable to or greater than that of the 0.25 mm lead equivalent, whereas the TCR thickness of 1.0 mm or greater provided a dose reduction comparable to that of the 0.35 mm lead equivalent.

CONCLUSIONS

Achieving a reduction of 95% or more requires the 0.25 mm lead equivalent for a distance of 100 cm, the 0.35 mm lead equivalent for 50 cm, the TCR thickness of 0.3 mm for 100 cm, or the TCR thickness of 0.9 mm for 50 cm. Without wearing a protective apron, a reduction of approximately 95% is observed at distances greater than 100 cm. These findings would be useful for medical staff engaging in related activities.

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

PURPOSE OF THE REPORT

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

nmCRPC, a look in the continuous care of prostate cancer patients: state of art and future perspectives

Non-metastatic castration resistant prostate cancer (nmCRPC) is a clinical setting defined as confirmed rising levels of PSA in patients treated with ADT but without detectable metastases on conventional imaging with computerized tomography (CT) and technetium-99 m scintigraphy. Men with nmCRPC and a PSA doubling time (PSADT) ≤ 10 months are considered at high risk of rapidly developing metastases with a consequent possible impact on survival. Three recent phase III trials have demonstrated, in this setting, the efficacy of adding a next-generation androgen receptor targeted agent (ARTA) to ADT in respect to ADT only, in delaying the development of metastases (metastasis-free survival, MFS) and prolong overall survival. The magnitude of clinical benefit of these agents was even more meaningful if considering the low incidence of drug related adverse events. Our review described the latest advances in the management of nmCRPC, deriving from the pivotal clinical trials, SPARTAN, PROSPER and ARAMIS, in order to support clinicians to optimally manage these patients. Of note, the emergence of novel, more accurate, next-generation imaging techniques (including Ga PSMA-PET/CT), as well as eventual future tumor biomarkers, is modifying the entity and definition of the nmCRPC setting, with a consequent impact on patient's diagnosis and management.

Altered Glucose Metabolism Postchemotherapy Precedes PSMA Expression in Poorly Differentiated Prostate Cancer

ABSTRACT

A 73-year-old man presented with gastric lesion on upper endoscopy, biopsy-proven as poorly differentiated carcinoma. Staging FDG PET/CT scan showed gastric, intraprostatic, nodal, and extensive osseous lesions. Prostate-specific antigen levels were greater than 1000. The patient was treated as metastatic poorly differentiated prostate cancer with chemotherapy. Posttherapy 18 F-PSMA-1007 and FDG PET/CT scans were obtained. PSMA PET/CT scan revealed extensive disease similar in appearance as staging FDG PET/CT scan, indicating no apparent treatment response. FDG PET/CT scan showed partial metabolic response, correlating with improved prostate-specific antigen levels. This case indicates that chemotherapy-induced changes in glucose metabolism likely precede change in PSMA expression in poorly differentiated prostate cancer.

Management of Patients with Recurrent and Metachronous Oligometastatic Prostate Cancer in the Era of PSMA PET

Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) scans have higher sensitivity and specificity for detecting lymph nodes or metastatic disease relative to conventional imaging in prostate cancer staging. Since its FDA approval and incorporation into treatment guidelines, the use of PSMA PET has increased in patients undergoing initial staging, those with recurrence after initial definitive treatment, and patients with metastatic disease. Although the early detection of metastatic lesions is changing disease management, it is unclear whether this impact on management translates into clinical benefit. This review will summarize evidence pertaining to the change in patient management due to PSMA PET use and will discuss the implications of PSMA PET on treatment decisions in prostate cancer, particularly in the settings of biochemical recurrence and metachronous oligometastatic disease.

Peptide Modification Diminishes HLA Class II-restricted CD4+ T Cell Recognition of Prostate Cancer Cells

Prostate cancer poses an ongoing problem in the western world accounting for significant morbidity and mortality in the male population. Current therapy options are effective in treating most prostate cancer patients, but a significant number of patients progress beyond a manageable disease. For these patients, immunotherapy has emerged as a real option in the treatment of the late-stage metastatic disease. Unfortunately, even the most successful immunotherapy strategies have only led to a four-month increase in survival. One issue responsible for the shortcomings in cancer immunotherapy is the inability to stimulate helper CD4⁺ T cells via the HLA class II pathway to generate a potent antitumor response. Obstacles to proper HLA class II stimulation in prostate cancer vaccine design include the lack of detectable class II proteins in prostate tumors and the absence of defined class II specific prostate tumor antigens. Here, for the first time, we show that the insertion of a lysosomal thiol reductase (GILT) into prostate cancer cells directly enhances HLA class II antigen processing and results in increased CD4⁺ T cell activation by prostate cancer cells. We also show that GILT insertion does not alter the expression of prostate-specific membrane antigen (PSMA), an important target in prostate cancer vaccine strategies. Our study suggests that GILT expression enhances the presentation of the immunodominant PSMA₄₅₉ epitope via the HLA class II pathway. Biochemical analysis showed that the PSMA₄₅₉ peptide was cysteinylated under a normal physiologic concentration of cystine, and this cysteinylated form of PSMA₄₅₉ inhibited T cell activation. Taken together, these results suggest that GILT has the potential to increase HLA class II Ag presentation and CD4⁺ T cell recognition of prostate cancer cells, and GILT-expressing prostate cancer cells could be used in designing cell therapy and/or vaccines against prostate cancer.

Failure Patterns by PSMA PET for Recurrent Prostate Cancer after Prostatectomy and Salvage Radiation

OBJECTIVE

To characterize patterns of failure using prostate-specific membrane antigen positron emission tomography (PSMA PET) after radical prostatectomy (RP) and salvage radiotherapy (SRT).

METHODS

Patients with rising PSA post-RP+SRT underwent 68Ga-HBED-iPSMA PET/CT on a single-arm, prospective imaging trial (NCT03204123). Scans were centrally reviewed with pattern-of-failure analysis by involved site. Positive scans were classified using 3 failure categories: pelvic nodal, extra-pelvic nodal or distant non-nodal. Associations with failure categories were analyzed using cumulative incidence and generalized logits regression.

RESULTS

We included 133 men who received SRT a median of 20 months post-RP; 56% received SRT to the prostatic fossa alone, while 44% received pelvic SRT. PSMA PET/CT was performed a median of 48 months post-SRT. Overall, 31% of PSMA PET/CT scans were negative, 2% equivocal and 67% had at least 1 positive site. Scan detection was significantly associated with PSA level prior to PSMA PET/CT. Analysis of 89 positive scans demonstrated pelvic nodal (53%) was the most common relapse and fossa relapse was low (9%). Overall, positive scans were pelvic (n = 35, 26%), extra-pelvic nodal (n = 26, 20%) or distant non-nodal failure (n = 28, 21%), and 70% of positive scans were oligorecurrent. We observed similar cumulative incidence for all failure categories and relatively few clinicodemographic associations. Men treated with pelvic SRT had reduced odds of pelvic failure versus exclusive fossa treatment.

CONCLUSION

Pelvic, extra-pelvic nodal, and distant non-nodal failures occur with similar incidence post-SRT. Regional nodal relapse is relatively common, especially with fossa-only SRT. A high oligorecurrence rate suggests a potentially important role for PSMA-guided focal therapies.

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.

Evaluation of [68 Ga]Ga-PSMA-I&T PET/CT with additional late scans of the pelvis in prostate-specific antigen recurrence using the PROMISE criteria

Background

PSMA PET/CT is the recommended imaging test in cases with prostate-specific antigen (PSA) recurrence after primary therapy of prostate cancer (PCa). However, imaging protocols remain a topic of active research. The aim of the presented study was to examine the impact of additional late scans of the pelvis in [⁶⁸ Ga]Ga-PSMA-I&T PET/CT of patients with rising PSA after prostatectomy.

Methods

A total of 297 patients (median PSA 0.35 ng/ml, interquartile range (IQR) 0.2–0.8) who underwent early whole-body [⁶⁸ Ga]Ga-PSMA-I&T PET/CT (median dose 141 MBq, IQR 120–163; median 86 min, IQR 56–107) and additional late scans of the pelvis (median 180 min, IQR 170–191) were investigated retrospectively. Early and late images were staged separately according to the PROMISE criteria and compared with a final consensus of both. Standardized uptake values were analyzed for early and late scans.

Results

One hundred and thirty-four (45.1%) [⁶⁸ Ga]Ga-PSMA-I&T PET/CT showed evidence of recurrent PCa (114/38.4% early, 131/44.1% late). Of 195 lesions, 144 (73.8%) were identified correctly on early scans. 191 (97.9%) lesions were detected on late imaging. The lesion SUVmax (median 3.4, IQR 0.4–6.5 vs. median 3.9, IQR 2.6–8.2) as well as the SUVmax to background ratio (median 9.4, IQR 1.7–19.1 vs. median 15.5, IQR 9.6–34.1) increased significantly between the imaging time points (p < 0.01, respectively). Compared to the final consensus, the miTNM-staging of early scans changed in 58 (19.5%) cases. Of these, 31 patients (10.4%) with negative early scans (T0 N0 M0) were upstaged. Twenty-seven (9.1%) patients with PCa characteristic lesions on early imaging (> T0 N0 M0) were up- and/or downstaged. In 4 (1.3%) cases, PCa-related lesions were only detectable on early PET/CT leading to upstagings of late imaging.

Conclusions

Additional late scans of the pelvis in [⁶⁸ Ga]Ga-PSMA-I&T PET/CT detected more lesions and an increasing contrast compared to early imaging. This influenced the final miTNM-staging substantially.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-022-00938-3.

The impact of PSMA PET on the treatment and outcomes of men with biochemical recurrence of prostate cancer: a systematic review and meta-analysis

BACKGROUND

Prostate-specific membrane antigen (PSMA) PET is highly sensitive in identifying disease recurrence in men with biochemical recurrence of prostate cancer (BCR) after primary therapy and is rapidly being adopted in clinical practice. The purpose of this systematic review and meta-analysis was to assess the documented impact of PSMA-PET on patient management and outcomes, including prostate-specific antigen (PSA) response, and intermediate and long-term outcome measures.

MATERIALS AND METHODS

MBASE, PubMed, Web of Science, Cochrane and OVID databases were searched for studies reporting on the impact of PSMA-PET on the management and outcomes of patients with BCR after definitive primary therapy. Outcome measures assessed included biochemical response to therapy after PET and BCR-free survival (BRFS). The proportions of patients in whom management changed, and the proportion of patients in whom each outcome measure was obtained were tabulated and pooled into meta-analysis using DerSimonian-Laird method.

RESULTS

A total of 34 studies with 3680 men reported change in management after PSMA-PET and 27 studies with 2639 men reported on at least one outcome measure and had follow-up data. PSMA-PET was positive in 2508/3680 (68.2%). The pooled proportion of change in management after PSMA-PET was 56.4% (95% CI, 48.0-63.9%). A decrease in serum PSA was documented in 72.4% of men (95% CI, 63.4-81.5%), and complete biochemical response in 23.3% (95% CI, 14.6-32.0%) at a median follow-up of 8.1 and 11 months, respectively. The pooled BRFS rate was 60.2% (95% CI, 49.1-71.4%) at a median follow-up of 20 months.

CONCLUSION

In conclusion, PSMA PET is positive in more than 2/3 of men with BCR and impacts patient management in more than half of the men. BRFS after PET-directed management is 60% at a median of 20 months after salvage therapy, and complete biochemical response may be achieved in up to a quarter of men.

Androgen Receptor Signaling in Prostate Cancer and Therapeutic Strategies

Understanding of the molecular mechanisms of prostate cancer has led to development of therapeutic strategies targeting androgen receptor (AR). These androgen-receptor signaling inhibitors (ARSI) include androgen synthesis inhibitor-abiraterone and androgen receptor antagonists-enzalutamide, apalutamide, and darolutamide. Although these medications provide significant improvement in survival among men with prostate cancer, drug resistance develops in nearly all patients with time. This could be through androgen-dependent or androgen-independent mechanisms. Even weaker signals and non-canonical steroid ligands can activate AR in the presence of truncated AR-splice variants, AR overexpression, or activating mutations in AR. AR splice variant, AR-V7 is the most studied among these and is not targeted by available ARSIs. Non-androgen receptor dependent resistance mechanisms are mediated by activation of an alternative signaling pathway when AR is inhibited. DNA repair pathway, PI3K/AKT/mTOR pathway, BRAF-MAPK and Wnt signaling pathway and activation by glucocorticoid receptors can restore downstream signaling in prostate cancer by alternative proteins. Multiple clinical trials are underway exploring therapeutic strategies to overcome these resistance mechanisms.

Rational Linker Design to Accelerate Excretion and Reduce Background Uptake of Peptidomimetic PSMA-Targeting Hybrid Molecules

The evolution of peptidomimetic hybrid molecules for preoperative imaging and guided surgery targeting the prostate-specific membrane antigen (PSMA) significantly progressed over the past few years, and some approaches are currently being evaluated for further clinical translation. However, accumulation in nonmalignant tissue such as kidney, bladder, spleen, or liver might limit tumor-to-background contrast for precise lesion delineation, particularly in a surgical setting. To overcome these limitations, a rational linker design aims at the development of a second generation of PSMA-11-based hybrid molecules with an enhanced pharmacokinetic profile and improved imaging contrast. Methods: A selection of rationally designed linkers was introduced to the PSMA-targeting hybrid molecule Glu-urea-Lys-HBED-CC-IRDye800CW, resulting in a second-generation peptidomimetic hybrid molecule library. The biologic properties were investigated in cell-based assays. In a preclinical proof-of-concept study with the radionuclide 68Ga, the impact of the modifications was evaluated by determination of specific tumor uptake, pharmacokinetics, and fluorescence imaging in tumor-bearing mice. Results: The modified hybrid molecules carrying various selected linkers revealed high PSMA-specific binding affinity and effective internalization. The highest tumor-to-background contrast of all modifications investigated was identified for the introduction of a histidine- (H) and glutamic acid (E)-containing linker ((HE)3-linker) between the PSMA-binding motif and the chelator. In comparison to the parental core structure, uptake in nonmalignant tissue was significantly reduced to a minimum, as exemplified by an 11-fold reduced spleen uptake from 38.12 ± 14.62 percentage injected dose (%ID)/g to 3.47 ± 1.39 %ID/g (1 h after injection). The specific tumor uptake of this compound (7.59 ± 0.95 %ID/g, 1 h after injection) was detected to be significantly higher than that of the parental tracer PSMA-11. These findings confirmed by PET and fluorescence imaging are accompanied by an enhanced pharmacokinetic profile with accelerated background clearance at early time points after injection. Conclusion: The novel generation of PSMA-targeting hybrid molecules reveals fast elimination, reduced background organ enrichment, and high PSMA-specific tumor uptake meeting the key demands for potent tracers in nuclear medicine and fluorescence-guided surgery. The approach's efficacy in improving the pharmacokinetic profile highlights the strengths of rational linker design as a powerful tool in strategic hybrid-molecule development.

The Role of Prostate-specific Membrane Antigen Positron Emission Tomography/Magnetic Resonance Imaging in Primary and Recurrent Prostate Cancer: A Systematic Review of the Literature

CONTEXT

Prostate-specific membrane antigen (PSMA) positron emission tomography/magnetic resonance imaging (PET/MRI) is a novel imaging technique with several potential applications in the prostate cancer (PCa) setting.

OBJECTIVE

To perform a systematic review of the current evidence regarding the diagnostic performance of PSMA PET/MRI in patients with primary and recurrent PCa.

EVIDENCE ACQUISITION

A comprehensive bibliographic search on the MEDLINE and Cochrane Library databases was performed in October 2020. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Studies were deemed eligible if they assessed patients with primary or recurrent PCa (P) undergoing PSMA PET/MRI (I) with or without comparison with other imaging techniques (C) in order to evaluate its diagnostic performance (O). Retrospective and prospective primary clinical studies were included. Results of previous meta-analyses were reported.

EVIDENCE SYNTHESIS

A total of 23 original articles and three meta-analyses were included. Limited evidence on PSMA PET/MRI is available, especially in the setting of partial gland ablation. PET/MRI can be an effective imaging modality for detecting primary PCa, showing higher accuracy than multiparametric MRI alone. It provides accurate local staging of primary PCa; however, there are contradictory results in this context when its performance is compared with other imaging techniques. PET/MRI also shows high performance for restaging and detecting tumor recurrence, even at low prostate-specific antigen levels.

CONCLUSIONS

PSMA PET/MRI could represent a valuable tool in the management of patients with primary and recurrent PCa. No specific recommendations can be provided.

PATIENT SUMMARY

Encouraging data regarding the benefits of prostate-specific membrane antigen positron emission tomography/magnetic resonance imaging in patients with prostate cancer are emerging from the literature.

Darolutamide Potentiates the Antitumor Efficacy of a PSMA-targeted Thorium-227 Conjugate by a Dual Mode of Action in Prostate Cancer Models

PURPOSE

Androgen receptor (AR) inhibitors are well established in the treatment of castration-resistant prostate cancer and have recently shown efficacy also in castration-sensitive prostate cancer. Although most patients respond well to initial therapy, resistance eventually develops, and thus, more effective therapeutic approaches are needed. Prostate-specific membrane antigen (PSMA) is highly expressed in prostate cancer and presents an attractive target for radionuclide therapy. Here, we evaluated the efficacy and explored the mode of action of the PSMA-targeted thorium-227 conjugate (PSMA-TTC) BAY 2315497, an antibody-based targeted alpha-therapy, in combination with the AR inhibitor darolutamide.

EXPERIMENTAL DESIGN

The in vitro and in vivo antitumor efficacy and mode of action of the combination treatment were investigated in preclinical cell line-derived and patient-derived prostate cancer xenograft models with different levels of PSMA expression.

RESULTS

Darolutamide induced the expression of PSMA in androgen-sensitive VCaP and LNCaP cells in vitro, and the efficacy of darolutamide in combination with PSMA-TTC was synergistic in these cells. In vivo, the combination treatment showed synergistic antitumor efficacy in the low PSMA-expressing VCaP and in the high PSMA-expressing ST1273 prostate cancer models, and enhanced efficacy in the enzalutamide-resistant KUCaP-1 model. The treatments were well tolerated. Mode-of-action studies revealed that darolutamide induced PSMA expression, resulting in higher tumor uptake of PSMA-TTC, and consequently, higher antitumor efficacy, and impaired PSMA-TTC-mediated induction of DNA damage repair genes, potentially contributing to increased DNA damage.

CONCLUSIONS

These results provide a strong rationale to investigate PSMA-TTC in combination with AR inhibitors in patients with prostate cancer.

Radiation Therapy After Radical Prostatectomy: What Has Changed Over Time?

The role and timing of radiotherapy (RT) in prostate cancer (PCa) patients treated with radical prostatectomy (RP) remains controversial. While recent trials support the oncological safety of early salvage RT (SRT) compared to adjuvant RT (ART) in selected patients, previous randomized studies demonstrated that ART might improve recurrence-free survival in patients at high risk for local recurrence based on adverse pathology. Although ART might improve survival, this approach is characterized by a risk of overtreatment in up to 40% of cases. SRT is defined as the administration of RT to the prostatic bed and to the surrounding tissues in the patient with PSA recurrence after surgery but no evidence of distant metastatic disease. The delivery of salvage therapies exclusively in men who experience biochemical recurrence (BCR) has the potential advantage of reducing the risk of side effects without theoretically compromising outcomes. However, how to select patients at risk of progression who are more likely to benefit from a more aggressive treatment after RP, the exact timing of RT after RP, and the use of hormone therapy and its duration at the time of RT are still open issues. Moreover, what the role of novel imaging techniques and genomic classifiers are in identifying the most optimal post-operative management of PCa patients treated with RP is yet to be clarified. This narrative review summarizes most relevant published data to guide a multidisciplinary team in selecting appropriate candidates for post-prostatectomy radiation therapy.

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.

Prostate Cancer Theranostics: From Target Description to Imaging

Prostate-specific membrane antigen-PET/computed tomography (PSMA-PET/CT) is the investigation of choice for imaging prostate cancer. Demonstrating high diagnostic accuracy, PSMA-PET/CT detects disease at very early stages of recurrence, where the chances of a definitive cure may be at their greatest. A number of PSMA-radioligands are in established clinical routine, and there are currently only limited data and no single tracer can clearly be advocated over the others at present. Further clinical trial data, comparing and contrasting radiotracers and reporting outcome-based data are necessary to further increase the implementation of this very promising imaging modality.

Pathologically Node-Positive Prostate Cancer: Casting for Cure When the Die Is Cast?

The postoperative management of men with lymph node involved prostate cancer (pN+) remains a challenge as there is a general lack of randomized trial data and a range of management strategies. Retrospective studies suggest a variable clinic course for patients with pN+ prostate cancer. Some men progress rapidly to metastatic disease despite further therapies, whereas other men can have a period of prolonged quiescence without adjuvant androgen deprivation therapy (ADT) or radiation therapy (RT). For men who have undergone radical prostatectomy, randomized trial data indicate that the addition of ADT in pN+ disease extends metastasis-free, prostate cancer-specific, and overall survival. Additional retrospective studies suggest that adding RT is potentially beneficial in this setting, improving overall and cancer-specific survival especially in men with certain pathologic parameters. Conversely, men with lower disease burden in their lymph nodes have longer times to progression and may be candidates for observation and salvage therapy as opposed to adjuvant ADT/RT.

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.

68Ga-Prostate-specific membrane antigen (psma) positron emission tomography (pet) in prostate cancer: a systematic review and meta-analysis

Introduction:

Prostate cancer (PC) is the second most commonly diagnosed cancer in males. ⁶⁸Ga-PSMA PET/CT, a non-invasive diagnostic tool to evaluate PC with prostate-specific membrane antigen (PSMA) expression, has emerged as a more accurate alternative to assess disease staging. We aimed to identify predictors of positive ⁶⁸Ga-PSMA PET and the accuracy of this technique.

Materials and methods:

Diagnostic accuracy cross-sectional study with prospective and retrospective approaches. We performed a comprehensive literature search on PubMed, Cochrane Library, and Embase database in search of studies including PC patients submitted to radical prostatectomy or radiotherapy with curative intent and presented biochemical recurrence following ASTRO 1996 criteria. A total of 35 studies involving 3910 patients submitted to 68-Ga-PSMA PET were included and independently assessed by two authors: 8 studies on diagnosis, four on staging, and 23 studies on restaging purposes. The significance level was α=0.05.

Results:

pooled sensitivity and specificity were 0.90 (0.86-0.93) and 0.90 (0.82-0.96), respectively, for diagnostic purposes; as for staging, pooled sensitivity and specificity were 0.93 (0.86-0.98) and 0.96 (0.92-0.99), respectively. In the restaging scenario, pooled sensitivity and specificity were 0.76 (0.74-0.78) and 0.45 (0.27-0.58), respectively, considering the identification of prostate cancer in each described situation. We also obtained specificity and sensitivity results for PSA subdivisions.

Conclusion:

⁶⁸Ga-PSMA PET provides higher sensitivity and specificity than traditional imaging for prostate cancer.

Prostate-specific Membrane Antigen PET in Prostate Cancer

Prostate-specific membrane antigen (PSMA)-targeted radiopharmaceuticals are playing a large role at the time of initial staging and biochemical recurrence for localizing prostate cancer, as well as in other emerging clinical settings. PSMA PET has demonstrated increased detection rate compared with conventional imaging and has been shown to change management plans in a substantial percentage of cases. The aims of this narrative review are to highlight the development and clinical impact of PSMA PET radiopharmaceuticals, to compare PSMA to other agents such as fluorine 18 fluciclovine and carbon 11 choline, and to highlight some of the individual PSMA PET agents that have contributed to the advancement of prostate cancer imaging.

A Phase II, Open-label study to assess safety and management change using 68Ga-THP PSMA PET/CT in patients with high risk primary prostate cancer or biochemical recurrence after radical treatment: The PRONOUNCED study

Objectives: To assess the safety and clinical impact of a novel, kit-based formulation of 68Ga-THP PSMA positron emission tomography/computed tomography (PET/CT) when used to guide the management of patients with prostate cancer (PCa). Methods: Patients were prospectively recruited in to one of: Group A: high-risk untreated prostate cancer; Gleason score >4+3, or PSA >20 ng/mL or clinical stage >T2c. Group B: biochemical recurrence (BCR) and eligible for salvage treatment after radical prostatectomy with two consecutive rises in prostate specific antigen (PSA) with a three month interval in between reads and final PSA >0.1 ng/mL or a PSA level >0.5 ng/mL. Group C: BCR with radical curative radiotherapy or brachytherapy at least three months prior to enrolment, and an increase in PSA level >2.0 ng/mL above the nadir level after radiotherapy or brachytherapy. Patients underwent evaluation with PET/CT 60 minutes following intravenous administration of 160±30 MBq of 68Ga-THP PSMA. Safety was assessed by means including vital signs, cardiovascular profile, serum haematology, biochemistry, urinalysis, PSA, and Adverse Events (AEs). A change in management was reported when the predefined clinical management of the patient altered as a result of 68Ga-THP PSMA PET/CT findings. Results: Forty-nine patients were evaluated with PET/CT; 20 in Group A, 21 in Group B and 8 in Group C. No patients experienced serious AEs discontinued the study due to AEs, or died during the study. Two patients had Treatment Emergent AEs attributed to 68Ga-THP-PSMA (pruritus in one patient and intravenous catheter site rash in another). Management change secondary to PET/CT occurred in 42.9% of all patients; 30% in Group A, 42.9% in Group B and 75% in Group C. Conclusion: 68Ga-THP PSMA was safe to use with no serious AE and no AE resulting in withdrawal from the study. 68Ga-THP PSMA PET/CT changed the management of patients in 42.9% of the study population, comparable to studies using other PSMA tracers. These data form the basis of a planned Phase III study of 68Ga-THP PSMA in patients with prostate cancer.

Detection efficacy of 18F-rhPSMA-7.3 PET/CT and impact on patient management in patients with biochemical recurrence of prostate cancer after radical prostatectomy and prior to potential salvage treatment

Purpose: Radiohybrid prostate-specific membrane antigen (rhPSMA) ligands are a new class of 18F-labeled PSMA-targeting agents. 18F-rhPSMA-7.3 is a lead compound which is currently under investigation in two multicenter phase III trials for PET-imaging. Here, we report the first retrospective data on its detection efficacy and potential impact on clinical management in a homogeneous cohort of patients with biochemical recurrence after radical prostatectomy, and prior to any salvage therapy. Methods: 242 patients (median [range] PSA, 0.60 [0.2-60.8] ng/mL) who underwent 18F-rhPSMA-7.3 PET/CT were retrospectively selected from the institutions' database. Images were re-read by an experienced nuclear medicine physician. Lesion detection rates were stratified by PSA. Further, potential management before and after PET was assessed by an interdisciplinary simulated tumor board and categorized (major vs. minor vs. no therapeutic change). The distribution of management change identified in each PSA subgroup was determined. Results: In total, 176/242 (72.7%) patients showed PSMA-ligand positive findings. 18F-rhPSMA-7.3 detection rates were 61.8% (63/102), 67.9% (38/56), 81.1% (30/37) and 95.7% (45/47) for PSA-levels of 0.2-<0.5 ng/mL, 0.5-<1 ng/mL, 1-<2 ng/mL and ≥2 ng/mL, respectively. 18F-rhPSMA-7.3 PET/CT revealed local recurrence, pelvic lymph node metastases, retroperitoneal lymph nodes metastases, supradiaphragmatic lymph nodes, bone metastases, and visceral metastases in 48.8% (n = 118), 28.9% (n = 70), 6.6% (n = 16), 1.2% (n = 3), 13.2% (n = 32) and 1.2% (n = 3) of patients, respectively. Notably, bone lesions were identified in 8.8% of patients (9/102) with PSA <0.5 ng/mL. Results from the interdisciplinary simulated tumor board indicated change of therapeutic management in 153/242 patients (63.2%) with 54/242 (22.3%) considered major and 99/242 (40.9%) minor, respectively. 18F-rhPSMA-7.3 PET/CT did not prompt any therapeutic changes in 64/242 patients (26.4%). Conclusion: 18F-rhPSMA-7.3 PET offers high detection efficacy in patients with biochemical recurrence after radical prostatectomy, and prior to potential salvage therapy, and results in a potential change in treatment plans in nearly 2/3 of patients. Keywords: Biochemical recurrence; hybrid imaging; positron emission tomography; prostate cancer; prostate-specific membrane antigen.

Seek and Find: Current Prospective Evidence for Prostate-specific Membrane Antigen Imaging to Detect Recurrent Prostate Cancer

CONTEXT

Men with biochemically relapsed prostate cancer face a clinical conundrum. Depending on the detected distribution of disease, treatment goals may range from cure with focal therapy to palliative with systemic therapy to expectant observation. Retrospective studies of prostate-specific membrane antigen (PSMA)-based imaging demonstrate higher disease detection rates than conventional imaging.

OBJECTIVE

This review focuses on available prospective evidence for diagnostic use of PSMA-based imaging to accurately restage recurrent prostate cancer and explores the potential clinical impact, near future uses, and challenges for PSMA-based imaging in this setting.

EVIDENCE ACQUISITION

PubMed and EMBASE databases were searched for prospective studies with primary, secondary, or exploratory endpoints evaluating PSMA-based imaging for patients with recurrent prostate cancer published in English in the past 10 yrs.

EVIDENCE SYNTHESIS

We reviewed 48 prospective studies evaluating the role of PSMA positron emission tomography (PET) in recurrent prostate cancer. These studies establish the diagnostic accuracy and safety of PSMA PET using the 68Ga-PSMA-11 and 18F-DCFPyL radiotracers even at lower prostate-specific antigen (PSA) levels (0.5 ≤ PSA < 1.0 ng/m: disease detection rate 51-78%). The use of PSMA PET has been shown to result in changes in management in up to two-thirds of patients.

CONCLUSIONS

There is now higher-level regulatory-quality prospective evidence for PSMA-based imaging for the detection of recurrent prostate cancer. There is prospective evidence of superiority over cross-sectional imaging and bone scintigraphy, as well as for the alterations in disease management as a result of PSMA-based imaging.

PATIENT SUMMARY

When the prostate-specific antigen (PSA) level is rising after primary therapy, prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is excellent at detecting and localizing prostate cancer, even at low PSA levels. Those who benefit best from treatment modifications based on PSMA PET findings are yet to be defined.

New frontiers in focal therapy for prostate cancer: Prostate-specific membrane antigen positron emission tomography/magnetic resonance imaging

Imaging has a central role in the context of focal therapy (FT) for prostate cancer (PCa). Prostate-specific membrane antigen (PSMA) positron emission tomography/magnetic resonance imaging (PET/MRI) is a novel imaging modality that combines the morpho-functional information of MRI with the molecular characterization of PET. Some papers reported the potential advantages of PSMA PET/MRI in different clinical scenarios. Limited evidence on PSMA PET/MRI is available in the setting of FT. PSMA PET/MRI can be an effective imaging modality for detecting primary PCa and seems to provide accurate local staging of primary PCa. PSMA PET/MRI also shows high performance for restaging and detecting tumor recurrence. The higher soft-tissue contrast and the reduction of ionizing radiation are the main advantages reported in the literature compared to PET/computed tomography. PSMA PET/MRI could represent a turning point in the management of patients with PCa in the context of FT. Further studies are needed to confirm its applications in this specific clinical setting.

Cytoplasmic Localization of Prostate-Specific Membrane Antigen Inhibitors May Confer Advantages for Targeted Cancer Therapies

Targeted imaging and therapy approaches based on novel prostate-specific membrane antigen (PSMA) inhibitors have fundamentally changed the treatment regimen of prostate cancer. However, the exact mechanism of PSMA inhibitor internalization has not yet been studied, and the inhibitors' subcellular fate remains elusive. Here, we investigated the intracellular distribution of peptidomimetic PSMA inhibitors and of PSMA itself by stimulated emission depletion (STED) nanoscopy, applying a novel nonstandard live cell staining protocol. Imaging analysis confirmed PSMA cluster formation at the cell surface of prostate cancer cells and clathrin-dependent endocytosis of PSMA inhibitors. Following the endosomal pathway, PSMA inhibitors accumulated in prostate cancer cells at clinically relevant time points. In contrast with PSMA itself, PSMA inhibitors were found to eventually distribute homogeneously in the cytoplasm, a molecular condition that promises benefits for treatment as cytoplasmic and in particular perinuclear enrichment of the radionuclide carriers may better facilitate the radiation-mediated damage of cancerous cells. This study is the first to reveal the subcellular fate of PSMA/PSMA inhibitor complexes at the nanoscale and aims to inspire the development of new approaches in the field of prostate cancer research, diagnostics, and therapeutics. SIGNIFICANCE: This study uses STED fluorescence microscopy to reveal the subcellular fate of PSMA/PSMA inhibitor complexes near the molecular level, providing insights of great clinical interest and suggestive of advantageous targeted therapies. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/8/2234/F1.large.jpg.

Evaluation of 18F-DCFPyL PSMA PET/CT for Prostate Cancer: A Meta-Analysis

Background

To systematically review the clinical value of 18F-DCFPyL prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) in the diagnosis of prostate cancer (PCa).

Methods

Literature concerning 18F-DCFPyL PSMA PET/CT in the diagnosis of prostate cancer published from 2015 to 2020 was electronically searched in the databases including PubMed and Embase. Statistical analysis was carried out with STATA 15 software, and the quality of included studies was tested with quality assessment of diagnostic accuracy studies (QUADAS) items. The heterogeneity of the included data was tested.

Results

In total, nine pieces of literature involving 426 patients met the inclusion criteria. The heterogeneity of the study group was not obvious. The SEN, SPE, LR+, LR−, DOR as well as AUC of 18F-DCFPyL PSMA PET/CT diagnosis of prostate cancer were 0.91, 0.90, 8.9, 0.10, 93, and 0.93. The pooled DR of 18F-DCFPyL labeled PSMA PET/CT in PCa was 92%. The pooled DR was 89% for PSA≥0.5 ng/ml and 49% for PSA < 0.5ng/ml.

Conclusion

18F-DCFPyL PSMA PET/CT had good sensitivity and specificity for the diagnosis of prostate cancer. The DR of 18F-DCFPyL PSMA PET/CT was correlated with PSA value. Further large-sample, high-quality studies were needed.

Clinical Utility of 18F-PSMA-1007 Positron Emission Tomography/Magnetic Resonance Imaging in Prostate Cancer: A Single-Center Experience

Purpose

This study aimed to evaluate the clinical utility of ¹⁸F-PSMA-1007 positron emission tomography (PSMA PET)/magnetic resonance imaging (MRI) imaging in patients with suspected or defined prostate cancer.

Methods

In the pilot study, we retrospectively investigated 62 patients who underwent PSMA-PET/MRI for suspected or defined PCa between June 2019 and June 2020. Patients were grouped into three subgroups: (1) suspected PCa without histological evidence, (2) primary PCa, (3) biochemical recurrent prostate cancer (BRPCa). Two nuclear physicians independently interpreted the results of PSMA-PET/MRI. Management strategies before PSMA-PET/MRI were retrospectively reported, and the management strategy was re-evaluated for each patient considering the PSMA-PET/MRI result. The changes in strategies were recorded. Besides, the correlation between prostate specific antigen (PSA) level and management changes was also accessed by Fisher exact test, and two-side p < 0.05 was assumed as statistical significance.

Results

There were 28 patients in the suspected PCa group (group 1), 12 in the primary PCa group (group 2), and 22 in the BRPCa group (group 3). Overall, the intended decisions were changed in 26 (41.9%) of 62 patients after PSMA-PET/MRI, including 11/28 (39.3%) in suspected PCa group, 1/12 (8.4%) in primary PCa group, and 14/24 (63.6%) in BCR group. In group 1, the main impact on subsequent management included decreased active surveillance (from 20 to 9) and increased prostate biopsy (from 8 to 19). PSA levels were not significantly associated with management changes in suspected PCa patients (p = 0.865). In group 2, the main impact on subsequent management included decreased radical surgery (from 8 to 7), and multimodal therapy appearance (n = 1). Only in the category of PSA levels of ≥20 ng/ml, the management of primary PCa was changed. In group 3, the main impact on subsequent management included decreased salvage radiotherapy (from 5 to 2), increased systemic therapy (from 6 to 7), and increased multimodal therapy (from 11 to 13). The highest proportion of management changes occurred in BCR patients with 0.5≤PSA<1 ng/ml.

Conclusion

From our preliminary experience, PSMA-PET/MRI may be a valued tool for defining PCa lesions and changing management. The biggest impact of management intent was in patients with BRPCa, especially in patients with 0.5≤PSA<1 ng/ml. However, further studies are needed to confirm our pilot findings.

Consensus statements on PSMA PET/CT response assessment criteria in prostate cancer

PURPOSE

Prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) is used for (re)staging prostate cancer (PCa) and as a biomarker for evaluating response to therapy, but lacks established response criteria. A panel of PCa experts in nuclear medicine, radiology, and/or urology met on February 21, 2020, in Amsterdam, The Netherlands, to formulate criteria for PSMA PET/CT-based response in patients treated for metastatic PCa and optimal timing to use it.

METHODS

Panelists received thematic topics and relevant literature prior to the meeting. Statements on how to interpret response and progression on therapy in PCa with PSMA PET/CT and when to use it were developed. Panelists voted anonymously on a nine-point scale, ranging from strongly disagree (1) to strongly agree (9). Median scores described agreement and consensus.

RESULTS

PSMA PET/CT consensus statements concerned utility, best timing for performing, criteria for evaluation of response, patients who could benefit, and handling of radiolabeled PSMA PET tracers. Consensus was reached on all statements. PSMA PET/CT can be used before and after any local and systemic treatment in patients with metastatic disease to evaluate response to treatment. Ideally, PSMA PET/CT imaging criteria should categorize patients as responders, patients with stable disease, partial response, and complete response, or as non-responders. Specific clinical scenarios such as oligometastatic or polymetastatic disease deserve special consideration.

CONCLUSIONS

Adoption of PSMA PET/CT should be supported by indication for appropriate use and precise criteria for interpretation. PSMA PET/CT criteria should categorize patients as responders or non-responders. Specific clinical scenarios deserve special consideration.

[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.

Lesion-to-background ratio threshold value of SUVmax of simultaneous [68Ga]Ga-PSMA-11 PET/MRI imaging in patients with prostate cancer

Purpose

This study aimed to calculate an applicable relative ratio threshold value instead of the absolute threshold value for simultaneous ⁶⁸Ga prostate-specific membrane antigen/positron emission tomography ([⁶⁸Ga]Ga-PSMA-11 PET) in patients with prostate cancer (PCa).

Materials and methods

Our study evaluated thirty-two patients and 170 focal prostate lesions. Lesions are classified into groups according to Prostate Imaging Reporting and Data System (PI-RADS). Standardized uptake values maximum (SUVmax), corresponding lesion-to-background ratios (LBRs) of SUVmax, and LBR distributions of each group were measured based on regions of interest (ROI). We examined LBR with receiver operating characteristic analysis to determine threshold values for differentiation between multiparametric magnetic resonance imaging (mpMRI)-positive and mpMRI-negative lesions.

Results

We analyzed a total of 170 focal prostate lesions. Lesions number of PI-RADS 2 to 5 was 70, 16, 46, and 38. LBR of SUVmax of each PI-RADS scores was 1.5 (0.9, 2.4), 2.5 (1.6, 3.4), 3.7 (2.6, 4.8), and 6.7 (3.5, 12.7). Based on an optimal threshold ratio of 2.5 to be exceeded, lesions could be classified into MRI-positive lesion on [⁶⁸Ga]Ga-PSMA PET with a sensitivity of 85.2%, a specificity of 72.0%, with the corresponding area under the receiver operating characteristic curve (AUC) of 0.83, p < 0.001. This value matches the imaging findings better.

Conclusion

The ratio threshold value of SUVmax, LBR, has improved clinical and research applicability compared with the absolute value of SUVmax. A higher threshold value than the background’s uptake can dovetail the imaging findings on MRI better. It reduces the bias from using absolute background uptake value as the threshold value.