68Ga-PSMA I&T PET/CT for primary staging of prostate cancer

Navigating the evolving diagnostic and therapeutic landscape of low- and intermediate-risk prostate cancer

ABSTRACT

In this nonsystematic review of the literature, we explored the changing landscape of detection and treatment of low- and intermediate-risk prostate cancer (PCa). Through emphasizing improved cancer assessment with histology classification and genomics, we investigated key developments in PCa detection and risk stratification. The pivotal role of prostate magnetic resonance imaging (MRI) in the novel diagnostic pathway is examined, alongside the benefits and drawbacks of MRI-targeted biopsies for detection and tumor characterization. We also delved into treatment options, particularly active surveillance for intermediate-risk PCa. Outcomes are compared between intermediate- and low-risk patients, offering insights into tailored management. Surgical techniques, including Retzius-sparing surgery, precision prostatectomy, and partial prostatectomy for anterior cancer, are appraised. Each technique has the potential to enhance outcomes and minimize complications. Advancements in technology and radiobiology, including computed tomography (CT)/MRI imaging and positron emission tomography (PET) fusion, allow for precise dose adjustment and daily target monitoring with imaging-guided radiotherapy, opening new ways of tailoring patients' treatments. Finally, experimental therapeutic approaches such as focal therapy open new treatment frontiers, although they create new needs in tumor identification and tracking during and after the procedure.

Scalability study on [133La]LaCl3 production with a focus on potential clinical applications

BACKGROUND

In recent years, targeted alpha therapy has gained importance in the clinics, and in particular, the alpha-emitter 225Ac plays a fundamental role in this clinical development. Nevertheless, depending on the chelating system no real diagnostic alternative has been established which shares similar chemical properties with this alpha-emitting radionuclide. In fact, the race to launch a diagnostic radionuclide to form a matched pair with 225Ac is still open, and 133La features attractive radiation properties to claim this place. However, in order to enable its translation into clinical use, upscaling of the production of this PET radionuclide is needed.

RESULTS

A study on optimal irradiation parameters, separation conditions and an exhaustive product characterization was carried out. In this framework, a proton irradiation of 2 h, 60 µA and 18.7 MeV produced 133La activities of up to 10.7 GBq at end of bombardment. In addition, the performance of four different chromatographic resins were tested and two optimized purification methods presented, taking approximately 20 min with a 133La recovery efficiencies of over 98%, decay corrected. High radionuclide purity and apparent molar activity was proved, of over 99.5% and 120 GBq/µmol, respectively, at end of purification. Furthermore, quantitative complexation of PSMA-617 and mcp-M-PSMA were obtained with molar activities up to 80 GBq/µmol. In addition, both 133La-radioconjugates offered high stability in serum, of over (98.5 ± 0.3)% and (99.20 ± 0.08)%, respectively, for up to 24 h. A first dosimetry estimation was also performed and it was calculated that an 133La application for imaging with between 350 and 750 MBq would only have an effective dose of 2.1-4.4 mSv, which is comparable to that of 18F and 68Ga based radiopharmaceuticals.

CONCLUSIONS

In this article we present an overarching study on 133La production, from the radiation parameters optimization to a clinical dose estimation. Lanthanum-133 activities in the GBq range could be produced, formulated as [133La]LaCl3 with high quality regarding radiolabeling and radionuclide purity. We believe that increasing the 133La availability will further promote the development of radiopharmaceuticals based on macropa or other chelators suitable for 225Ac.

Quantitative PSMA-PET parameters in localized prostate cancer: prognostic and potential predictive value

BACKGROUND

PSMA-PET is increasingly used for staging prostate cancer (PCA) patients. However, it is not clear if quantitative imaging parameters of positron emission tomography (PET) have an impact on disease progression and are thus important for the prognosis of localized PCA.

METHODS

This is a monocenter retrospective analysis of 86 consecutive patients with localized intermediate or high-risk PCA and PSMA-PET before treatment The quantitative PET parameters maximum standardized uptake value (SUVmax), tumor asphericity (ASP), PSMA tumor volume (PSMA-TV), and PSMA total lesion uptake (PSMA-TLU = PSMA-TV × SUVmean) were assessed for their prognostic significance in patients with radiotherapy or surgery. Cox regression analyses were performed for biochemical recurrence-free survival, overall survival (OS), local control, and loco-regional control (LRC).

RESULTS

67% of patients had high-risk disease, 51 patients were treated with radiotherapy, and 35 with surgery. Analysis of metric PET parameters in the whole cohort revealed a significant association of PSMA-TV (p = 0.003), PSMA-TLU (p = 0.004), and ASP (p < 0.001) with OS. Upon binarization of PET parameters, several other parameters showed a significant association with clinical outcome. When analyzing high-risk patients according to the primary treatment approach, a previously published cut-off for SUVmax (8.6) showed a significant association with LRC in surgically treated (p = 0.048), but not in primary irradiated (p = 0.34) patients. In addition, PSMA-TLU (p = 0.016) seemed to be a very promising biomarker to stratify surgical patients.

CONCLUSION

Our data confirm one previous publication on the prognostic impact of SUVmax in surgically treated patients with high-risk PCA. Our exploratory analysis indicates that PSMA-TLU might be even better suited. The missing association with primary irradiated patients needs prospective validation with a larger sample size to conclude a predictive potential. Trial registration Due to the retrospective nature of this research, no registration was carried out.

Diagnostic Performance of [18F]AlF-Thretide PET/CT in Patients with Newly Diagnosed Prostate Cancer Using Histopathology as Reference Standard

This study aimed to assess the diagnostic value of [18F]AlF-thretide PET/CT in patients with newly diagnosed prostate cancer (PCa). Methods: In total, 49 patients with biopsy-proven PCa were enrolled in this prospective study. All patients underwent [18F]AlF-thretide PET/CT, and the scoring system of the PRIMARY trial was used for PET image analysis. The dosimetry evaluation of [18F]AlF-thretide was performed on 3 patients. Pathologic examination was used as the reference standard to evaluate the location, number, size, and Gleason score of tumors, for comparison with the [18F]AlF-thretide PET/CT results. PSMA expression was evaluated by immunohistochemical staining. Results: All patients tolerated the [18F]AlF-thretide PET/CT well. The total effective dose of [18F]AlF-thretide was 1.16E-02 mSv/MBq. For patient-based analysis of intraprostatic tumors, 46 of 49 (93.9%) patients showed pathologic uptake on [18F]AlF-thretide PET/CT. For lesion-based analysis of intraprostatic tumors, the sensitivity and positive predictive value for [18F]AlF-thretide PET/CT were 58.2% and 90.5%, respectively. Delayed images can detect more lesions than standard images (n = 57 vs. 49, P = 0.005), and the SUVmax and tumor-to-background ratio of the former were higher than those of the latter (SUVmax: 14.5 ± 16.7 vs. 11.4 ± 13.6, P < 0.001; tumor-to-background ratio: 37.1 ± 42.3 vs. 23.1 ± 27.4, P < 0.001). The receiver-operating-characteristic curve analysis showed that the areas under the curve for PRIMARY score-predicted true-positive and false-positive lesions were significantly higher than those for the SUVmax of standard images (P = 0.015) and seemed higher than those for the SUVmax of delayed images (P = 0.257). [18F]AlF-thretide PET/CT showed a higher detection rate than multiparametric MRI for all intraprostatic foci (53.5% vs. 40.8%, P = 0.012) and clinically significant PCa (75.0% vs. 61.4%, P = 0.031). Conclusion: [18F]AlF-thretide PET/CT showed high diagnostic value for patients with primary PCa and can be used as an excellent imaging modality for preoperative evaluation of PCa patients.

Diagnostic Accuracy of Molecular Imaging Techniques for Detecting Prostate Cancer: A Systematic Review

Molecular imaging modalities show valuable non-invasive techniques capable of precisely and selectively addressing molecular markers associated with prostate cancer (PCa). This systematic review provides an overview of imaging markers utilized in positron emission tomography (PET) methods, specifically focusing on the pathways and mediators involved in PCa. This systematic review aims to evaluate and analyse existing literature on the diagnostic accuracy of molecular imaging techniques for detecting PCa. The PubMed, EBSCO, ScienceDirect, and Web of Science databases were searched, identifying 32 studies that reported molecular imaging modalities for detecting PCa. Numerous imaging modalities and radiotracers were used to detect PCa, including 68Ga-prostate-specific membrane antigen (PSMA) PET/computed tomography (CT), 68Ga-PSMA-11 PET/magnetic resonance imaging (MRI), 18F-PSMA-1007 PET/CT, 18F-DCFPyL PET/MRI, 18F-choline PET/MRI, and 18F-fluoroethylcholine PET/MRI. Across 11 studies, radiolabelled 68Ga-PSMA PET/CT imaging had a pooled sensitivity of 80 (95% confidence interval [CI]: 35-93), specificity of 90 (95% CI: 71-98), and accuracy of 86 (95% CI: 64-96). The PSMA-ligand 68Ga-PET/CT showed good diagnostic performance and appears promising for detecting and staging PCa.

Advancements in PSMA ligand radiolabeling for diagnosis and treatment of prostate cancer: a systematic review

Prostate cancer(PCa), a leading global health concern, profoundly impacts millions of men worldwide. Progressing through two stages, it initially develops within the prostate and subsequently extends to vital organs such as lymph nodes, bones, lungs, and the liver. In the early phases, castration therapy is often employed to mitigate androgen effects. However, when prostate cancer becomes resistant to this treatment, alternative strategies become imperative. As diagnostic and treatment methodologies for prostate cancer continually advance, radioligand therapy (RLT) has emerged as a promising avenue, yielding noteworthy outcomes. The fundamental principle of RLT involves delivering radionuclide drugs to cancerous lesions through specific carriers or technologies. Subsequently, these radionuclide drugs release radioactive energy, facilitating the destruction of cancer cell tissues. At present, the positron emission tomography (PET) targeting PSMA has been widely developed for the use of diagnosis and staging of PCa. Notably, FDA-approved prostate-specific membrane antigen (PSMA) targeting agents, such as 68Ga-PSMA-11 and 177Lu-PSMA-617, represent significant milestones in enhancing diagnostic precision and therapeutic efficacy. This review emphasizes the current research status and outcomes of various radionuclide-labeled PSMA ligands. The objective is to provide valuable insights for the continued advancement of diagnostic and therapeutic approaches in the realm of prostate cancer.

[99mTc]Tc-HYNIC-ALUG SPECT/CT in the initial staging of 227 consecutive patients with newly diagnosed prostate cancer: a 5-year monocentric retrospective study

Purpose

The purpose of this study was to assess the effectiveness of [99mTc]Tc-HYNIC-ALUG SPECT/CT in the initial staging of patients with newly diagnosed PCa.

Methods

A retrospective analysis was conducted on 227 consecutive patients who underwent [99mTc]Tc-HYNIC-ALUG SPECT/CT imaging for the primary staging of newly diagnosed PCa. The presence and location of PSMA-positive lesions were determined, and the maximum standardized uptake values (SUVmax) of the primary prostate tumor were also measured. The metastatic findings and SUVmax were stratified according to International Society of Urological Pathology (ISUP) grade, prostate-specific antigen (PSA) levels, and D'Amico classification. Furthermore, the [99mTc]Tc-HYNIC-ALUG SPECT/CT findings were compared to the histopathological findings in patients who had undergone radical prostatectomy with pelvic lymph node dissection (PLND).

Results

Of the 227 patients, 92.1% (209/227) had positive [99mTc]Tc-HYNIC-ALUG SPECT/CT findings. Advanced disease was detected in 38.8% (88/227) of the patients and was positively correlated with increasing ISUP grade and PSA levels. Lymph node metastases (both pelvic and extrapelvic), bone metastases, and visceral metastases were detected in 30.0% (68/227), 25.6% (58/227), and 3.1% (7/227) of the patients, respectively. For the 129 patients who underwent radical prostatectomy with PLND, the sensitivity of [99mTc]Tc-HYNIC-ALUG SPECT/CT in the evaluation of PCa was 90.7% (117/129). The sensitivity, specificity, accuracy, and positive and negative predictive values for detecting pelvic lymph node metastases on [99mTc]Tc-HYNIC-ALUG SPECT/CT were 23.5% (12/51), 93.6% (73/78), 65.9% (85/129), 70.6% (12/17), and 65.2% (73/112), respectively. Among the 209 patients with PSMA-avid primary prostate disease, the SUVmax of the primary prostate tumor was significantly associated with ISUP grade (p<0.0001), PSA levels (p<0.0001), D'Amico classification (p<0.0001), and advanced disease (p<0.0001). Receiver operating characteristic (ROC) analysis revealed that a PSA level >19.8 ng/ml and SUVmax of the primary prostate tumor >7.4 had a sensitivity of 71.6% and 71.6% and specificity of 76.9% and 82.6%, respectively, for detecting metastatic disease.

Conclusions

[99mTc]Tc-HYNIC-ALUG SPECT/CT emerges as a valuable imaging tool for the initial staging of newly diagnosed PCa. The presence of advanced disease and the SUVmax of the primary prostate tumor were positively correlated with ISUP grade and PSA levels.

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.

"One Method to Label Them All": A Single Fully Automated Protocol for GMP-Compliant 68Ga Radiolabeling of PSMA-11, Transposable to PSMA-I&T and PSMA-617

BACKGROUND

Prostate-specific membrane antigen (PSMA) is an ideal target for molecular imaging and targeted radionuclide therapy in prostate cancer. Consequently, various PSMA ligands were developed. Some of these molecules are functionalized with a chelator that can host radiometals, such as 68Ga for PET imaging. The 68Ga radiolabeling step benefits from process automation, making it more robust and reducing radiation exposure.

OBJECTIVE

To design a single automated radiolabeling protocol for the GMP-compliant preparation of [68Ga]Ga-PSMA-11, transposable to the production of [68Ga]Ga-PSMA-617 and [68Ga]Ga-PSMA-I&T.

METHODS

A GAIA® synthesis module and a GALLIAD® generator were used. Radio-TLC and radio-HPLC methods were validated for radiochemical purity (RCP) determination. Three [68Ga]Ga-PSMA-11 validation batches were produced and thoroughly tested for appearance and pH, radionuclide identity and purity, RCP, stability, residual solvent and sterility. Minimal modifications were made to the reagents and disposables for optimal application to other PSMA ligands.

RESULTS

[68Ga]Ga-PSMA-11 for clinical application was produced in 27 min. The 3 validation batches met the quality criteria expected by the European Pharmacopoeia to allow routine production. For optimal transposition to PSMA-617, the solid phase extraction cartridge was changed to improve purification of the radiolabeled product. For application to PSMA-I&T, the buffer solution initially used was replaced by HEPES 2.7 M to achieve good radiochemical yields. Residual HEPES content was checked in the final product and was below the Ph. Eur. threshold.

CONCLUSION

A single automated radiolabeling method on the GAIA® module was developed and implemented for 68Ga radiolabeling of 3 PSMA ligands, with slight adjustments for each molecule.

PSMA PET/CT for Primary Staging of Prostate Cancer - An Updated Overview

Prostate-specific membrane antigen PET/CT for primary staging of prostate cancer is becoming increasingly popular due to simultaneous assessment of whole-body disease burden, with superior sensitivity and specificity for detecting metastases compared to conventional imaging. PSMA PET in combination with multiparametric MRI (mpMRI) improves the sensitivity of assessment of extra-prostatic extension and seminal vesicle invasion compared to mpMRI alone, and may serve as a second line modality for image-guided biopsy in selected patients with negative mpMRI and/or negative primary biopsies. The superior diagnostic accuracy of PSMA PET/CT affects clinical decision-making with a change of clinical management in one-fourth of patients compared to conventional imaging. However, at present, the effect of implementing PSMA PET/CT for primary staging on patient outcomes is not clear, and prospective studies are warranted. There are several PSMA tracers with similar performance and minor individual pharmacokinetic differences such as higher rate of unspecific bone uptake with 18F-PSMA-1007, but on the other hand, lower urinary excretion, which could give an advantage in the detection of local recurrence. Proper training of the reporting physicians and knowledge of the pitfalls of the specific PSMA tracer used is of utmost importance for high-quality reading. We aim to provide an overview of the current literature and an update on the status of PSMA PET/CT for primary staging of prostate cancer.

Comparison of Multiparametric MRI, [68Ga]Ga-PSMA-11 PET-CT, and Clinical Nomograms for Primary T and N Staging of Intermediate-to-High-Risk Prostate Cancer

PURPOSE OF THE REPORT

Although multiparametric magnetic resonance imaging (mpMRI) is commonly used for the primary staging of prostate cancer, it may miss non-enlarged metastatic lymph nodes. Positron emission tomography-computed tomography targeting the prostate-specific membrane antigen (PSMA PET-CT) is a promising method to detect non-enlarged metastatic lymph nodes, but more data are needed.

MATERIALS AND METHODS

In this single-center, prospective study, we enrolled patients with intermediate-to-high-risk prostate cancer scheduled for radical prostatectomy with pelvic node dissection. Before surgery, prostate imaging with mpMRI and PSMA PET-CT was used to assess lymph node involvement (LNI), extra-prostatic extension (EPE), and seminal vesicle involvement (SVI). Additionally, we used clinical nomograms to estimate the risk of these three outcomes.

RESULTS

Of the 74 patients included, 61 (82%) had high-risk prostate cancer, and the rest had intermediate-risk cancer. Histopathology revealed LNI in 20 (27%) patients, SVI in 26 (35%), and EPE in 52 (70%). PSMA PET-CT performed better than mpMRI at detecting LNI (area under the curve (AUC, 95% confidence interval): 0.779 (0.665-0.893) vs. 0.655 (0.529-0.780)), but mpMRI was better at detecting SVI (AUC: 0.775 (0.672-0.878) vs. 0.585 (0.473-0.698)). The MSKCC nomogram performed well at detecting both LNI (AUC: 0.799 (0.680-0.918)) and SVI (0.772 (0.659-0.885)). However, when the nomogram was used to derive binary diagnoses, decision curve analyses showed that the MSKCC nomogram provided less net benefit than mpMRI and PSMA PET-CT for detecting SVI and LNI, respectively.

CONCLUSIONS

mpMRI and [68Ga]Ga-PSMA-11 PET-CT are complementary techniques to be used in conjunction for the primary T and N staging of prostate cancer.

Early biochemical and radiographic response after one cycle of [177Lu]Lu-PSMA I&T radioligand therapy in metastatic castration-resistant prostate cancer patients

PURPOSE

The aim of this study was to investigate very early radiographic PSMA PET response after one cycle of [177Lu]Lu-PSMA I&T radioligand therapy (RLT) of metastatic castration-resistant prostate cancer (mCRPC) and to assess its role in predicting overall response and survival.

METHODS

This retrospective study enrolled 40 mCRPC patients who were treated with a median of 3 (2-9) [177Lu]Lu-PSMA I&T RLT cycles. Biochemical response was based on the relative change of serum PSA according to PCWG3 criteria, while radiographic response referred to the relative change of PSMA-derived total viable tumor volumes expressed as total lesion PSMA (TLP).

RESULTS

After one cycle of RLT, biochemical partial response (PR) was seen in 8/40 (20.0%), stable disease (SD) in 22/40 (55.0%), and progressive disease (PD) in 10/40 (25%) patients. In PSMA PET, very early molecular PR was observed in 12 (30.0%), SD in 19 (47.5%), and PD in 9 (22.5%) subjects. The PSA and TLP nadir were achieved after a median of 1 (1-5) and 2 (1-6) cycles, respectively. Nineteen (47.5%) patients showed overall biochemical PR, 11 (27.5%) had SD, and 10 (25%) experienced PD. In PSMA-directed PET, 4 patients experienced molecular complete response (CR), 24 (60.0%) had PR, 4 (10.0%) SD, and 8 (20.0%) PD. Early biochemical or radiographic response was not associated with longer overall survival (OS). Overall biochemical responders had a nearly significantly longer median OS (22.7 months) than non-responders (14.4 months, p = 0.08). Early PSA progression was associated with shorter OS (12.2 months), compared to biochemical SD/PR (18.7 months, p = 0.09).

CONCLUSION

In this retrospective cohort, there was no association between early PSMA PET radiographic response and overall survival; hence, treatment should not be prematurely discontinued. In contrast, early PSA progression after one cycle of [177Lu]Lu-PSMA I&T RLT was an indicator of overall progression and poor clinical outcome.

68Ga-PSMA PET/CT-based multivariate model for highly accurate and noninvasive diagnosis of clinically significant prostate cancer in the PSA gray zone

BACKGROUND

The prostate-specific antigen (PSA) has been widely used in screening and early diagnosis of prostate cancer (PCa). However, in the PSA grey zone of 4-10 ng/ml, the sensitivity and specificity for diagnosing PCa are limited, resulting in considerable number of unnecessary and invasive prostate biopsies, which may lead to potential overdiagnosis and overtreatment. We aimed to predict clinically significant PCa (CSPCa) by combining the maximal standardized uptake value (SUVmax) based on 68Ga‑PSMA PET/CT and clinical indicators in men with gray zone PSA levels.

METHODS

81 patients with suspected PCa based on increased serum total PSA (TPSA) levels of 4 - 10 ng/mL who underwent transrectal ultrasound/magnetic resonance imaging (MRI)/PET fusion-guided biopsy were enrolled. Among them, patients confirmed by histopathology were divided into the CSPCa group and the non-CSPCa group, and data on PSA concentration, prostate volume (PV), PSA density (PSAD), free PSA (FPSA)/TPSA, Prostate Imaging-Reporting and Data System version 2.1 (PI-RADS v2.1) score, 68Ga-PSMA PET/CT imaging evaluation results and SUVmax were compared. Multivariate logistic regression analysis was performed to identify the independent predictors for CSPCa, thereby establishing a predictive model based on SUVmax that was evaluated by analyzing the receiver operating characteristic (ROC) curve and decision curve analysis.

RESULTS

Compared to non-CSPCa, CSPCa patients had smaller PVs (median, 31.40 mL), lower FPSA/TPSA (median, 0.12), larger PSADs (median, 0.21 ng/mL2) and higher PI-RADS scores (P < 0.05). The prediction model comprising 68Ga-PSMA PET/CT maximal standardized uptake value, PV and FPSA/TPSA had the highest AUC of 0.927 compared with that of other predictors alone (AUCs of 0.585 for PSA, 0.652 for mpMRI and 0.850 for 68Ga-PSMA PET/CT). The diagnostic sensitivity and specificity of the prediction model were 86.21% and 86.54%, respectively.

CONCLUSION

Given the low diagnostic accuracy of regular PSA tests, a new prediction model based on the 68Ga-PSMA PET/CT SUVmax, PV and FPSA/TPSA was developed and validated, and this model could provide a more satisfactory predictive accuracy for CSPCa. This study provides a noninvasive prediction model with high accuracy for the diagnosis of CSPCa in the PSA gray zone, thus may be better avoiding unnecessary biopsy procedures.

A prospective head-to-head comparison of [68Ga]Ga-P16-093 and [68Ga]Ga-PSMA-11 PET/CT in patients with primary prostate cancer

PURPOSE

We aimed to compare the diagnostic performance and biodistribution of two similar PET agents, [68Ga]Ga-P16-093 and [68Ga]Ga-PSMA-11, in the same group of primary prostate cancer (PCa) patients.

METHODS

Fifty patients with untreated, histologically confirmed PCa by needle biopsy were enrolled. Each patient underwent [68Ga]Ga-P16-093 and [68Ga]Ga-PSMA-11 PET/CT within a week. In addition to visual analysis, the standardized uptake value (SUV) was measured for semiquantitative comparison and correlation analysis.

RESULTS

[68Ga]Ga-P16-093 PET/CT detected more positive tumors than [68Ga]Ga-PSMA-11 PET/CT (202 vs. 190, P = 0.002), both for intraprostatic lesions (48 vs. 41, P = 0.016) and metastatic lesions (154 vs. 149, P = 0.125), especially for intraprostatic lesions in low- and intermediate-risk PCa patients (21/23 vs. 15/23, P = 0.031). Furthermore, [68Ga]Ga-P16-093 PET/CT exhibited a significantly higher SUVmax for most matched tumors (13.7 ± 10.2 vs. 11.4 ± 8.3, P < 0.001). For normal organs, [68Ga]Ga-P16-093 PET/CT showed significantly lower activity in the kidney (SUVmean: 20.1 ± 6.1 vs. 29.3 ± 9.1, P < 0.001) and urinary bladder (SUVmean: 6.5 ± 7.1 vs. 20.9 ± 17.4, P < 0.001), but displayed a higher uptake in the parotid gland (SUVmean: 8.7 ± 2.6 vs. 7.6 ± 2.1, P < 0.001), liver (SUVmean: 7.0 ± 1.9 vs. 3.7 ± 1.3, P < 0.001), and spleen (SUVmean: 8.2 ± 3.0 vs. 5.2 ± 2.2, P < 0.001) than [68Ga]Ga-PSMA-11 PET/CT.

CONCLUSION

[68Ga]Ga-P16-093 PET/CT demonstrated higher tumor uptake and better tumor detectability than [68Ga]Ga-PSMA-11 PET/CT, especially in low- and intermediate-risk PCa patients, which indicated that [68Ga]Ga-P16-093 may serve as an alternative agent for detection of PCa.

TRIAL REGISTRATION

68Ga-P16-093 and 68Ga-PSMA-11 PET/CT Imaging in the Same Group of Primary Prostate Cancer Patients (NCT05324332, Registered 12 April 2022, retrospectively registered). URL OF REGISTRY: https://clinicaltrials.gov/ct2/show/NCT05324332 .

Up-to-Date Imaging and Diagnostic Techniques for Prostate Cancer: A Literature Review

Prostate cancer (PCa) faces great challenges in early diagnosis, which often leads not only to unnecessary, invasive procedures, but to over-diagnosis and treatment as well, thus highlighting the need for modern PCa diagnostic techniques. The review aims to provide an up-to-date summary of chronologically existing diagnostic approaches for PCa, as well as their potential to improve clinically significant PCa (csPCa) diagnosis and to reduce the proliferation and monitoring of PCa. Our review demonstrates the primary outcomes of the most significant studies and makes comparisons across the diagnostic efficacies of different PCa tests. Since prostate biopsy, the current mainstream PCa diagnosis, is an invasive procedure with a high risk of post-biopsy complications, it is vital we dig out specific, sensitive, and accurate diagnostic approaches in PCa and conduct more studies with milestone findings and comparable sample sizes to validate and corroborate the findings.

Development of [177Lu]Lu-LNC1003 for radioligand therapy of prostate cancer with a moderate level of PSMA expression

PURPOSE

Evans blue as an albumin binder has been widely used to improve pharmacokinetics and enhance tumor uptake of radioligands, including prostate-specific membrane antigen (PSMA) targeting agents. The goal of this study is to develop an optimal Evans blue-modified radiotherapeutic agent that could maximize the absolute tumor uptake and tumor absorbed dose thus the therapeutic efficacy to allow treatment of tumors even with moderate level of PSMA expression.

METHODS

[177Lu]Lu-LNC1003 was synthesized based on PSMA-targeting agent and Evans blue. Binding affinity and PSMA targeting specificity were verified through cell uptake and competition binding assay in 22Rv1 tumor model that has moderate level of PSMA expression. SPECT/CT imaging and biodistribution studies in 22Rv1 tumor-bearing mice were performed to evaluate the preclinical pharmacokinetics. Radioligand therapy studies were conducted to systematically assess the therapeutic effect of [177Lu]Lu-LNC1003.

RESULTS

LNC1003 showed high binding affinity (IC50 = 10.77 nM) to PSMA in vitro, which was comparable with that of PSMA-617 (IC50 = 27.49 nM) and EB-PSMA-617 (IC50 = 7.91 nM). SPECT imaging of [177Lu]Lu-LNC1003 demonstrated significantly improved tumor uptake and retention as compared with [177Lu]Lu-EB-PSMA and [177Lu]Lu-PSMA-617, making it suitable for prostate cancer therapy. Biodistribution studies further confirmed the remarkably higher tumor uptake of [177Lu]Lu-LNC1003 (138.87 ± 26.53%ID/g) over [177Lu]Lu-EB-PSMA-617 (29.89 ± 8.86%ID/g) and [177Lu]Lu-PSMA-617 (4.28 ± 0.25%ID/g) at 24 h post-injection. Targeted radioligand therapy results showed noteworthy inhibition of 22Rv1 tumor growth after administration of a single dose of 18.5 MBq [177Lu]Lu-LNC1003. There was no obvious antitumor effect after [177Lu]Lu-PSMA-617 treatment under the same condition.

CONCLUSION

In this study, [177Lu]Lu-LNC1003 was successfully synthesized with high radiochemical purity and stability. High binding affinity and PSMA targeting specificity were identified in vitro and in vivo. With greatly enhanced tumor uptake and retention, [177Lu]Lu-LNC1003 has the potential to improve therapeutic efficacy using significantly lower dosages and less cycles of 177Lu that promises clinical translation to treat prostate cancer with various levels of PSMA expression.

The Diagnostic Value of PSMA PET/CT in Men with Newly Diagnosed Unfavorable Intermediate-Risk Prostate Cancer

Our objective was to determine the diagnostic value of prostate-specific membrane antigen (PSMA) PET/CT in staging men with newly diagnosed unfavorable intermediate-risk prostate cancer (PCa). Methods: Patients with newly diagnosed unfavorable intermediate-risk PCa, in whom PSMA PET/CT was performed as a primary staging modality, were retrospectively studied. PSMA PET/CT was performed at several diagnostic centers and reported by expert nuclear medicine physicians within 2 high-volume PCa centers. A multivariate logistic regression analysis, taking into account clinical, biochemical, pathologic, and radiologic variables, was performed to identify potential independent predictors for metastatic disease on PSMA PET/CT. Results: In total, 396 men with newly diagnosed unfavorable intermediate-risk PCa were studied. Metastatic disease was observed in 37 (9.3%) men, of whom 29 (7.3%) had molecular imaging locoregional lymph node metastases (miN1) and 16 (4.0%) had distant metastases (miM1). A radiologic tumor stage of at least T3 on MRI (odds ratio, 2.72 [95% CI, 1.27-5.83]; P = 0.01) and more than 50% positive prostate biopsies (odds ratio, 3.87 [95% CI, 1.74-8.62]; P = 0.001) were found to be independently associated with metastatic disease on PSMA PET/CT. Conclusion: Given that metastatic disease was observed in nearly 1 in 10 men with newly diagnosed unfavorable intermediate-risk PCa, PSMA PET/CT is considered to be of diagnostic value within this population. Further stratification using the radiologic tumor stage and the percentage of positive prostate biopsies could aid in identifying those patients at risk of having metastatic disease on PSMA PET/CT.

The Application of Radiolabeled Targeted Molecular Probes for the Diagnosis and Treatment of Prostate Cancer

Radiopharmaceuticals targeting prostate-specific membrane antigens (PSMA) are essential for the diagnosis, evaluation, and treatment of prostate cancer (PCa), particularly metastatic castration-resistant PCa, for which conventional treatment is ineffective. These molecular probes include [⁶⁸Ga]PSMA, [¹⁸F]PSMA, [Al¹⁸F]PSMA, [^99mTc]PSMA, and [⁸⁹Zr]PSMA, which are widely used for diagnosis, and [¹⁷⁷Lu]PSMA and [²²⁵Ac]PSMA, which are used for treatment. There are also new types of radiopharmaceuticals. Due to the differentiation and heterogeneity of tumor cells, a subtype of PCa with an extremely poor prognosis, referred to as neuroendocrine prostate cancer (NEPC), has emerged, and its diagnosis and treatment present great challenges. To improve the detection rate of NEPC and prolong patient survival, many researchers have investigated the use of relevant radiopharmaceuticals as targeted molecular probes for the detection and treatment of NEPC lesions, including DOTA-TOC and DOTA-TATE for somatostatin receptors, 4A06 for CUB domain-containing protein 1, and FDG. This review focused on the specific molecular targets and various radionuclides that have been developed for PCa in recent years, including those mentioned above and several others, and aimed to provide valuable up-to-date information and research ideas for future studies.

A prospective comparative study of [68Ga]Ga-RM26 and [68Ga]Ga-PSMA-617 PET/CT imaging in suspicious prostate cancer

PURPOSE

Prostate-specific membrane antigen (PSMA)-based PET/CT imaging has limitations in the diagnosis of prostate cancer (PCa). We recruited 207 participants with suspicious PCa to perform PET/CT imaging with radiolabeled gastrin-releasing peptide receptor (GRPR) antagonist, [68Ga]Ga-RM26, and compare with [68Ga]Ga-PSMA-617 and histopathology.

METHODS

Every participant with suspicious PCa was scanned with both [68Ga]Ga-RM26 and [68Ga]Ga-PSMA-617 PET/CT. PET/CT imaging was compared using pathologic specimens as a reference standard.

RESULTS

Of the 207 participants analyzed, 125 had cancer, and 82 were diagnosed with benign prostatic hyperplasia (BPH). The sensitivity and specificity of [68Ga]Ga-RM26 and [68Ga]Ga-PSMA-617 PET/CT imaging differed significantly for detecting clinically significant PCa. The area under the ROC curve (AUC) was 0.54 for [68Ga]Ga-RM26 PET/CT and 0.91 for [68Ga]Ga-PSMA-617 PET/CT in detecting PCa. For clinically significant PCa imaging, the AUCs were 0.51 vs. 0.93, respectively. [68Ga]Ga-RM26 PET/CT imaging had higher sensitivity for PCa with Gleason score (GS) = 6 (p = 0.03) than [68Ga]Ga-PSMA-617 PET/CT but poor specificity (20.73%). In the group with PSA < 10 ng/mL, the sensitivity, specificity, and AUC of [68Ga]Ga-RM26 PET/CT were lower than [68Ga]Ga-PSMA-617 PET/CT (60.00% vs. 80.30%, p = 0.12, 23.26% vs. 88.37%, p = 0.000, and 0.524 vs. 0.822, p = 0.000, respectively). [68Ga]Ga-RM26 PET/CT exhibited significantly higher SUVmax in specimens with GS = 6 (p = 0.04) and in the low-risk group (p = 0.01), and its uptake did not increase with PSA level, GS, or clinical stage.

CONCLUSION

This prospective study provided evidence for the superior accuracy of [68Ga]Ga-PSMA-617 PET/CT over [68Ga]Ga-RM26 PET/CT in detecting more clinically significant PCa. [68Ga]Ga-RM26 PET/CT showed an advantage for imaging low-risk PCa.

Staging Prostate Cancer with 68Ga-PSMA-11 PET/CT in the Elderly: Is Preimaging Biopsy Imperative?

Although prostate-specific membrane antigen (PSMA) PET/CT has been shown valuable for staging biopsy-proven [B(+)] high-risk prostate cancer, elderly patients are occasionally referred for PSMA PET/CT without a preimaging confirming biopsy [B(-)]. The current study evaluated the rate, clinical characteristics, and PET-based stage of elderly B(-) patients and explored whether biopsy status affects therapeutic approach. Methods: One hundred consecutive patients at least 80 y old who underwent staging ⁶⁸Ga-PSMA-11 PET/CT were included. For each patient, we documented whether preimaging biopsy was performed, the clinical parameters, the PET-based staging parameters, and the primary therapy received. Results: Thirty-four (34%) of the elderly patients included in the study had no preimaging biopsy. Compared with B(+) patients, B(-) patients were older (median age, 87 vs. 82 y; P < 0.01), with worse performance status (P < 0.01) and higher prostate-specific antigen (PSA) levels (median, 57 vs. 15.4 ng/mL; P < 0.01). On ⁶⁸Ga-PSMA-11 PET/CT, all B(-) patients had avid disease, with trends toward higher rates of bone metastases (47.1% vs. 28.8%) and overall advanced disease (50% vs. 33.3%) than in B(+) patients. Among patients with localized (n = 36) or locally advanced (n = 25) disease, B(-) patients were less commonly referred than B(+) patients for definitive therapies (P < 0.01). However, higher age, Eastern Cooperative Oncology Group performance status, and PSA were other probable factors determining their therapeutic approach. Among 39 patients with advanced disease, 38 received hormonal therapy irrespective of their biopsy status. Among B(-) patients with advanced disease who were referred for hormonal therapy, 12 of 13 with follow-up data showed a biochemical or imaging-based response. Conclusion: Real-life experience with ⁶⁸Ga-PSMA-11 PET/CT indicates that around one third of elderly patients are referred for imaging without a preimaging confirming biopsy. These patients are likely to be older, with a worse clinical status and higher PSA levels. Advanced disease might be more likely to be identified on their ⁶⁸Ga-PSMA-11 PET/CT images, and if it is, their biopsy status does not preclude them from receiving hormonal therapy.

Head-to-head comparison of [68Ga]Ga-P16-093 and 2-[18F]FDG PET/CT in patients with clear cell renal cell carcinoma: a pilot study

PURPOSE

This pilot study was prospectively designed to evaluate and compare the diagnostic value of PET/CT using a PSMA-specific tracer [⁶⁸Ga]Ga-P16-093 and a glucose metabolism probe 2-[¹⁸F]FDG in clear cell renal cell carcinoma (ccRCC) patients.

METHODS

Forty-two pathologically confirmed ccRCC patients were included. Within 1 week, each patient underwent [⁶⁸Ga]Ga-P16-093 and 2-[¹⁸F]FDG PET/CT. In addition to visual analysis of tumor number, the standardized uptake value (SUV) was measured for semiquantitative comparison and correlation analysis.

RESULTS

For primary ccRCC patients, [⁶⁸Ga]Ga-P16-093 PET/CT demonstrated a significantly higher detection rate (19/22 vs. 13/22, P = 0.031) and higher tumor uptake (15.7 ± 9.0 vs. 5.1 ± 3.4, P < 0.001) than 2-[¹⁸F]FDG PET/CT. In addition, the SUVmax of the primary tumor on [⁶⁸Ga]Ga-P16-093 and 2-[¹⁸F]FDG PET/CT was significantly correlated with pT stage (for [⁶⁸Ga]Ga-P16-093, r = 0.550, P = 0.008; for 2-[¹⁸F]FDG, r = 0.514, P = 0.014) and WHO/ISUP grade (for [⁶⁸Ga]Ga-P16-093, r = 0.566, P = 0.006; for 2-[¹⁸F]FDG, r = 0.492, P = 0.020), respectively. For metastatic ccRCC patients, [⁶⁸Ga]Ga-P16-093 PET/CT also demonstrated a better detection rate (21/22 vs. 14/22, P = 0.008) and higher tumor uptake (11.0 ± 6.4 vs. 4.4 ± 2.7, P < 0.001) than 2-[¹⁸F]FDG PET/CT. The SUVmax on [⁶⁸Ga]Ga-P16-093 PET/CT had a significant association with PSMA expression in primary ccRCC (r = 0.776, P < 0.001) and metastatic ccRCC (r = 0.626, P = 0.029).

CONCLUSIONS

[⁶⁸Ga]Ga-P16-093 PET/CT demonstrates significantly better tumor detectability than 2-[¹⁸F]FDG PET/CT for ccRCC patients.

TRIAL REGISTRATION

⁶⁸Ga-P16-093 and ¹⁸F-FDG PET/CT Imaging in the Same Group of Clear Cell Renal Cell Carcinoma Patients (NCT05432947, Registered 27 June 2021, retrospectively registered) URL OF REGISTRY: https://clinicaltrials.gov/ct2/show/NCT05432947 .

Head-to-Head Comparison of 68 Ga-P16-093 and 68 Ga-PSMA-617 PET/CT in Patients With Primary Prostate Cancer : A Pilot Study

PURPOSE

We aimed to compare the diagnostic performance of 68 Ga-P16-093 and 68 Ga-PSMA-617 PET/CT in primary prostate cancer (PCa) patients.

PATIENTS AND METHODS

Thirty untreated primary PCa patients were enrolled. Each patient underwent 68 Ga-P16-093 and 68 Ga-PSMA-617 PET/CT within a week. In addition to visual analysis, SUV was measured for semiquantitative comparison and correlation analysis.

RESULTS

68 Ga-P16-093 PET/CT detected more positive tumors than 68 Ga-PSMA-617 PET/CT (67 vs 56, P = 0.002), especially for intraprostatic lesions (29 vs 24, P = 0.025) and lymph node metastases (23 vs 17, P = 0.034). Further, 68 Ga-P16-093 PET/CT exhibited significantly higher SUV max of matched tumors (18.3 ± 14.4 vs 13.9 ± 11.8, P < 0.001). Besides, the SUV max of high-risk patients (based on D'Amico classification) on 68 Ga-P16-093 PET/CT was significantly higher than that of low- and intermediate-risk PCa patients (20.9 ± 9.9 vs 8.9 ± 9.1 vs 10.1 ± 5.2, P = 0.007). The SUV max of tumor measured by 68 Ga-P16-093 PET/CT had a moderate association with biopsy Gleason score ( r = 0.462, P = 0.005) and prostate-specific antigen value ( r = 0.491, P = 0.002), and significantly correlated with PSMA expression ( r = 0.732, P < 0.001).

CONCLUSIONS

68 Ga-P16-093 PET/CT exhibited higher tumor uptake and potentially better tumor detection capability than 68 Ga-PSMA-617 PET/CT, which suggested that 68 Ga-P16-093 may be more suitable in the diagnosis and staging of primary PCa patients.

[Oncological theranostics in nuclear medicine]

The theranostic principle describes the diagnostic and therapeutic use of radioactive nuclides linked to biochemically active ligands. The oldest and most prominent field of application of theranostics in oncology is differentiated thyroid cancer treated by radioiodine therapy, which allows imaging of the iodine uptake and thus tumor manifestations by gamma (γ) radiation of radioiodine. Other areas of application include neuroendocrine tumors, castration-resistant prostate cancer and, in the context of individual therapeutic approaches, fibroblastic tumors. Imaging with beta-plus (β⁺) emitters is mainly performed using so-called hybrid imaging: positron emission tomography (PET) in combination with computed tomography or magnetic resonance imaging (PET/CT or PET/MRI). Beta-minus (β^-) emitters are predominantly used in therapy, but the use of alpha (α) emitters is also increasing, thus, enabling targeted cancer treatment with mostly low-grade side effects.

Prostate specific membrane antigen positron emission tomography in primary prostate cancer diagnosis: First-line imaging is afoot

Prostate specific membrane antigen positron emission tomography (PSMA PET) is an excellent molecular imaging technique for prostate cancer. Currently, PSMA PET for patients with primary prostate cancer is supplementary to conventional imaging techniques, according to guidelines. This supplementary function of PSMA PET is due to a lack of systematic review of its strengths, limitations, and potential development direction. Thus, we review PSMA ligands, detection, T, N, and M staging, treatment management, and false results of PSMA PET in clinical studies. We also discuss the strengths and challenges of PSMA PET. PSMA PET can greatly increase the detection rate of prostate cancer and accuracy of T/N/M staging, which facilitates more appropriate treatment for primary prostate cancer. Lastly, we propose that PSMA PET could become the first-line imaging modality for primary prostate cancer, and we describe its potential expanded application.

[89Zr]Zr-PSMA-617 PET/CT in biochemical recurrence of prostate cancer: first clinical experience from a pilot study including biodistribution and dose estimates

Purpose

Prostate-specific membrane antigen (PSMA)-targeted PET/CT has become increasingly important in the management of prostate cancer, especially in localization of biochemical recurrence (BCR). PSMA-targeted PET/CT imaging with long-lived radionuclides as ⁸⁹Zr (T_1/2 = 78.4 h) may improve diagnostics by allowing data acquisition on later time points. In this study, we present our first clinical experience including preliminary biodistribution and dosimetry data of [⁸⁹Zr]Zr-PSMA-617 PET/CT in patients with BCR of prostate cancer.

Methods

Seven patients with BCR of prostate cancer who revealed no (n = 4) or undetermined (n = 3) findings on [⁶⁸Ga]Ga-PSMA-11 PET/CT imaging were referred to [⁸⁹Zr]Zr-PSMA-617 PET/CT. PET/CT imaging was performed 1 h, 24 h, 48 h, and 72 h post injection (p.i.) of 111 ± 11 MBq [⁸⁹Zr]Zr-PSMA-617 (mean ± standard deviation). Normal organ distribution and dosimetry were determined. Lesions visually considered as suggestive of prostate cancer were quantitatively analyzed.

Results

Intense physiological uptake was observed in the salivary and lacrimal glands, liver, spleen, kidneys, intestine and urinary tract. The parotid gland received the highest absorbed dose (0.601 ± 0.185 mGy/MBq), followed by the kidneys (0.517 ± 0.125 mGy/MBq). The estimated overall effective dose for the administration of 111 MBq was 10.1 mSv (0.0913 ± 0.0118 mSv/MBq). In 6 patients, and in particular in 3 of 4 patients with negative [⁶⁸Ga]Ga-PSMA-11 PET/CT, at least one prostate cancer lesion was detected in [⁸⁹Zr]Zr-PSMA-617 PET/CT imaging at later time points. The majority of tumor lesions were first visible at 24 h p.i. with continuously increasing tumor-to-background ratio over time. All tumor lesions were detectable at 48 h and 72 h p.i.

Conclusion

[⁸⁹Zr]Zr-PSMA-617 PET/CT imaging is a promising new diagnostic tool with acceptable radiation exposure for patients with prostate cancer especially when [⁶⁸Ga]Ga-PSMA-11 PET/CT imaging fails detecting recurrent disease. The long half-life of ⁸⁹Zr enables late time point imaging (up to 72 h in our study) with increased tracer uptake in tumor lesions and higher tumor-to-background ratios allowing identification of lesions non-visible on [⁶⁸Ga]Ga-PSMA-11 PET/CT imaging.

Diverse PSMA expression in primary prostate cancer: reason for negative [68Ga]Ga-PSMA PET/CT scans? Immunohistochemical validation in 40 surgical specimens

PURPOSE

The purpose of this study was to immunohistochemically validate the primary tumor PSMA expression in prostate cancer (PCa) patients imaged with [⁶⁸Ga]Ga-PSMA PET/CT prior to surgery, with special consideration of PET-negative cases.

METHODS

The study included 40 men with newly diagnosed treatment-naïve PCa imaged with [⁶⁸Ga]Ga-PSMA I&T PET/CT as part of the diagnostic work-up prior to radical prostatectomy. All primary tumors were routinely stained with H&E. In addition, immunohistochemical staining of PSMA was performed and the immunoreactive score (IRS) was computed as semiquantitative measure. Subsequently, imaging findings were correlated to histopathologic results.

RESULTS

Eighty-three percent (33/40) of patients presented focal uptake of [⁶⁸Ga]Ga-PSMA I&T in the primary tumor in at least one prostate lobe. Among PSMA-PET positive patients, one-third had lymph node metastases (LNM) detected by post-operative histopathology, while in PET negative patients, only 1 out of 7 presented with regional LN involvement; PSMA-avid distant lesions, predominantly in bones, were observed in 15% and 0% of patients, respectively. The median IRS classification of PSMA expression in tumor tissue was 2 (range, 1-3) both in PSMA-PET positive and negative prostate lobes, with significantly different interquartile range: 2-3 vs. 2-2, respectively (p = 0.03). The median volume of PSMA-PET positive tumors was 5.4 mL (0.2-32.9) as compared to 1.6 mL (0.3-18.3) of PET-negative tumors (p < 0.001). There was a significant but weak correlation between SUV_max and percentage of PSMA-positive tumor cells (r = 0.46, p < 0.001). A total of 35/44 (~80%) lobes were positive in PSMA-PET imaging, when a cut-off percentage of PSMA-positive cells was ≥ 90%, while 19/36 (~53%) lobes with < 90% PSMA-positive cells were PSMA-PET negative.

CONCLUSION

Positive [⁶⁸Ga]Ga-PSMA I&T PET/CT scan of primary tumor of PCa results from a combination of factors, such as homogeneity and intensity of PSMA expression, tumor volume and grade, with a cutoff value of ≥ 90% PSMA-positive cells strongly determining PET-positivity. Focal accumulation of [⁶⁸Ga]Ga-PSMA in the primary tumor may correlate positively with aggressiveness of prostate cancer, harboring higher risk of regional LN involvement and distant metastatic spread.

Comparing the Diagnostic Performance of Multiparametric Prostate MRI Versus 68Ga-PSMA PET-CT in the Evaluation Lymph Node Involvement and Extraprostatic Extension

PURPOSE

Our research aims to compare the efficacy of PET and MRI for lymph node metastasis and extraprostatic extension in cases with newly diagnosed prostate cancer undergoing radical prostatectomy with extended pelvic lymph node dissection.

METHODS

Thirty-nine cases who underwent radical prostatectomy with pelvic lymph node dissection between June 2015 and January 2020 were included in the study. Patients with gallium (ga-68 Prostate-specific membrane antigen (PSMA) PET) PSMA PET-CT and multiparametric (mp) prostate MRI performed according to PIRADS v2 criteria in our clinic were included.

RESULTS

The extraprostatic extension was observed in 16 cases. The sensitivity of MR in detecting extracapsular invasion was calculated as 56.2%, specificity 82.6%, positive predictive value (PPV) 69.2%, negative predictive value (NPV) 73.0%. The sensitivity of PET was 62.5%, specificity 60.8%, PPV 52.6%, NPV 70%. Eleven lymph node metastases were observed in nine cases. The sensitivity, specificity, PPV and NPV of metastatic lymph node detection were; 36.3%, 99.6%, 57.1%, 99.0% for MRI and; 18.1%, 99.4%, 33.3%, 98.8% for PET CT, respectively.

CONCLUSION

Mp prostate MRI showed low sensitivity and high specificity compared to PSMA PET CT in extracapsular invasion evaluation. The sensitivity of both modalities in the detection of metastatic lymph nodes was low.

Correlation Between Quantitative PSMA PET Parameters and Clinical Risk Factors in Non-Metastatic Primary Prostate Cancer Patients

Background

PSMA PET is frequently used for staging of prostate cancer patients. Furthermore, there is increasing interest to use PET information for personalized local treatment approaches in surgery and radiotherapy, especially for focal treatment strategies. However, it is not well established which quantitative imaging parameters show highest correlation with clinical and histological tumor aggressiveness.

Methods

This is a retrospective analysis of 135 consecutive patients with non-metastatic prostate cancer and PSMA PET before any treatment. Clinical risk parameters (PSA values, Gleason score and D'Amico risk group) were correlated with quantitative PET parameters maximum standardized uptake value (SUVmax), mean SUV (SUVmean), tumor asphericity (ASP) and PSMA tumor volume (PSMA-TV).

Results

Most of the investigated imaging parameters were highly correlated with each other (correlation coefficients between 0.20 and 0.95). A low to moderate, however significant, correlation of imaging parameters with PSA values (0.19 to 0.45) and with Gleason scores (0.17 to 0.31) was observed for all parameters except ASP which did not show a significant correlation with Gleason score. Receiver operating characteristics for the detection of D'Amico high-risk patients showed poor to fair sensitivity and specificity for all investigated quantitative PSMA PET parameters (Areas under the curve (AUC) between 0.63 and 0.73). Comparison of AUC between quantitative PET parameters by DeLong test showed significant superiority of SUVmax compared to SUVmean for the detection of high-risk patients. None of the investigated imaging parameters significantly outperformed SUVmax.

Conclusion

Our data confirm prior publications with lower number of patients that reported moderate correlations of PSMA PET parameters with clinical risk factors. With the important limitation that Gleason scores were only biopsy-derived in this study, there is no indication that the investigated additional parameters deliver superior information compared to SUVmax.

68Ga-PSMA-11 PET/CT Initial Staging in Black and White South African Males with ISUP Grade Group 1 and 2 Prostate Adenocarcinoma

Prostate adenocarcinoma (PCa) is a leading cause of mortality. Black males with high-risk PCa have a poorer prognosis compared to white males. Patients with International Society of Urological Pathology (ISUP) Grade Group (GG) 1 and 2 PCa have little potential for metastases post radical prostatectomy. ⁶⁸Gallium prostate specific membrane antigen (⁶⁸Ga-PSMA) PET/CT imaging for metastatic PCa is superior to conventional imaging in staging high-risk PCa. No strong evidence is available to support imaging low-risk patients. We aimed to evaluate the value of ⁶⁸Ga-PSMA PET/CT in black and white South African (BSA and WSA) males with GG1 and 2 PCa at initial staging. We evaluated 25 WSA and 123 BSA males. The image findings were correlated with prostate specific antigen (PSA). PSA levels significantly correlated with both primary tumor and whole-body PSMA-tumor volume (PSMA-TV) and were higher in BSA males. No differences were noted in the occurrence of metastases; however, PSA, seminal vesicle invasion and black race predicted metastases. Our findings suggest higher PSMA expression and tumor burden in BSA with histologically low-risk PCa, and future research with immunohistochemistry evaluation will be essential to confirm these findings.

The role of Ga68 PSMA PET/CT imaging in Lu177 PSMA treatment planning in metastatic castration-resistant prostate cancer

OBJECTIVE

Lutetium-177 (Lu¹⁷⁷) prostate-specific membrane antigen (Lu¹⁷⁷ PSMA) is a novel targeted treatment for patients with metastatic castration-resistant prostate cancer (CRPC). The purpose of the study was to determine the molecular volumetric Gallium-68 (Ga⁶⁸) PSMA PET/CT parameters that can predict patients who will respond to treatment.

METHODS

These single-center retrospective data were obtained from metastatic CRPC patients receiving intravenous 6.0-8.5 GBq Lu¹⁷⁷ PSMA treatment every 6-8 weeks for a maximum of 3-8 cycles, with baseline Ga⁶⁸ PSMA PET/CT scan, clinical data, and information on treatment responses. All lesions were divided into two groups according to the increase and decrease in PSMA expression levels of 600 bone lesions and 85 lymph nodes that were compatible with metastasis of 23 patients after the treatment. The primary endpoint of our study was the evaluation of the relation between the baseline SUVmax, PSMA TV, TL PSMA values, and the treatment response of the two groups. The threshold values were determined for the parameters that had significant relations. In the present study, the prostate-specific antigen (PSA) response and treatment-induced toxicities were also evaluated as the secondary endpoint.

RESULTS

It was found that SUVmax, PSMA TV, and TL PSMA values in bone metastases showed significant differences between the groups with decreased and increased PSMA expression levels after the treatment. The AUC value for SUVmax was significant (AUC = 0.677; p < 0.001). The cutoff value was > 10.50 (sensitivity = 91.8%, Specificity = 41.5%) for SUVmax, > 1.50 cm³ (sensitivity = 49.1%, specificity = 70%) for PSMA TV and > 8.50 g (sensitivity = %60.9, specificity = %72.2) for TL PSMA. The median SUVmax value before the treatment in all metastatic lymph nodes was found to be 7.1 (5.4-12.4), and the median SUVmax after the treatment was 2.5 (1.6-12.1) (p < 0.001).

CONCLUSION

It was shown in the present study that Lu¹⁷⁷ PSMA treatment response may be higher in CRPC patients with metastatic bone lesion with high baseline PSMA expression level, and better treatment response may be achieved in patients with lymph node metastases than in bone metastases.

Time point-independent tumor positivity of 68Ga-PSMA-PET/CT pre- and post-biopsy in high-risk prostate cancer

OBJECTIVE

Prostate-specific membrane antigen (PSMA)-PET/CT imaging has gained increasing clinical importance for the detection and staging of high-risk primary prostate cancer (PCa). However, it is unclear whether the routine practice of prostate biopsy obscures the image finding of PSMA-PET/CT. This study aimed to compare the tumor positivity rate of PSMA-PET/CT performed pre- (PSMA-PET/CT_pre) and post-biopsy (PSMA-PET/CT_post) in high-risk PCa patients.

PATIENTS AND METHODS

We matched 58 PSMA-PET/CT_post with 58 PSMA-PET/CT_pre studies for primary detection of high-risk PCa according to clinical characteristics. Three subgroups of PSMA-PET/CT_post were defined by the intervals after biopsy (≤ 1 week, 1 ~ 2 weeks, and 2 ~ 5 weeks). Tumor positivity rates were determined, and SUVmax of primary tumors were compared separately for the two main groups and the related subgroups. Malignant prostate tissues from 20 of these patients were examined by immunohistochemical analysis of PSMA. In addition, the values of PSMA-PET/CT_pre and PSMA-PET/CT_post in assessing seminal vesicle invasion (SVI) were evaluated in patients who underwent radical prostatectomy.

RESULTS

All the primary tumors were positive on PSMA-PET/CT_post and PSMA-PET/CT_pre imaging, resulting in a patient-based positivity rates of 100% (58/58) in both groups. All examined IHC results (20/20) confirmed the high-level expression of PSMA. SUVmax of primary tumors did not differ between the two main groups (16.1, IQR 9.8-26.6 vs. 16.5, IQR 11.0-26.7, p > 0.05). Subgroup analysis of PSMA-PET/CT_post (≤ 1 week, 1 ~ 2 weeks, and 2 ~ 5 weeks) also showed no significant difference in tumor SUVmax (15.8, IQR 9.5-22.2; 17.8, IQR 9.8-29.2; and 15.4, IQR 10.1-30.3. p > 0.05). PSMA-PET/CT_post and PSMA-PET/CT_pre exhibited similar value in SVI detection as well.

CONCLUSIONS

The tumor positivity rate was consistently high for PSMA-PET/CT pre- and post-biopsy. A prior biopsy does not seem to affect the tumor positivity rate of PSMA-PET/CT in high-risk PCa.

Gallium-68 Prostate-Specific Membrane Antigen Positron Emission Tomography: A Practical Guide for Radiologists and Clinicians

Prostate cancer (PCa) is the third most common form of cancer and the most common cancer diagnosis in men in the United States. It is known that prostate-specific membrane antigen (PSMA) is overexpressed in PCa. PSMA is a type II transmembrane glycoprotein expressed in several benign and malignant tissues. In December 2020, FDA approved Gallium-68 (68Ga) PSMA, which is a PSMA-targeted positron emission tomography (PET) imaging agent. Molecular imaging targeting PSMA has shown substantial advancement in PCa imaging. In this article, we discuss the radiopharmaceutical, indications to do PSMA PET, technical aspects of PSMA PET imaging, normal biodistribution of PSMA, other benign and malignant conditions that can take up PSMA, staging of prostate cancer, and how to report PSMA PET.

Comparison of 68Ga-PSMA PET/CT and multiparametric MRI for the detection of low- and intermediate-risk prostate cancer

Purpose

To assess ⁶⁸Ga-PSMA PET/CT for detection of low- and intermediate-risk prostate cancer (PCa), high-risk PCa in comparison with mpMRI, respectively, and to determine which of low- and intermediate-risk PCa are more likely to be detected by ⁶⁸Ga-PSMA PET/CT.

Methods

We conducted a retrospective analysis of patients who had undergone a prostate biopsy and/or radical prostatectomy and who were scanned with ⁶⁸Ga-PSMA PET/CT and mpMRI between June 2019 and March 2021. The mpMRI images were scored with the Prostate Imaging-Reporting and Data System Version 2.1 (PI-RADS) and were classified as either negative (PI-RADS 1–3) or positive (PI-RADS 4–5). Suspicious ⁶⁸Ga-PSMA PET/CT lesions were reviewed for each relevant patient and classified by double-trained board-certified nuclear medicine physicians. The results were evaluated with the histopathological outcome. All patients were classified according to the D’Amico classification, and the clinical data were combined for stratified analysis.

Result

A total of 101 patients who were pathologically diagnosed with PCa were analyzed. Of the 101 patients, 88 (80.6%) patients presented with a pathologic mpMRI, and 85 (79.1%) with a pathologic ⁶⁸Ga-PSMA PET/CT. In the high-risk PCa cohort, ⁶⁸Ga-PSMA PET/CT was positive in 64/66 (97.0%) patients and yielded a higher detection rate than that for the mpMRI patients (58/66, 87.9%; p < 0.05). However, mpMRI provided superior diagnostic confidence in identifying low- and intermediate-risk PCa (30/35, 85.7% vs. 21/35, 60.0%; p < 0.05). When the age threshold exceeded 62.5 years and the serum prostate specific antigen (PSA) threshold exceeded 9.4 ng/ml, a higher uptake of PSMA was more likely to occur in the lesions of low- and intermediate-risk PCa.

Conclusion

The diagnostic performance of ⁶⁸Ga-PSMA PET/CT was superior to that of mpMRI in the high-risk PCa cohort, which was consistent with prior studies. Furthermore, in the initial diagnosis of low- and intermediate-risk PCa, we found that mpMRI showed a higher diagnostic accuracy than ⁶⁸Ga-PSMA PET/CT did. Low- and intermediate-risk PCa patients with a PSA ≥ 9.4 ng/ml and age ≥ 62.5 years were more likely to have a positive ⁶⁸Ga-PSMA PET/CT result.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-022-00881-3.

Renal Infarction Imaged With [18F]Prostate-Specific Membrane Antigen-1007 PET/CT

ABSTRACT

A 61-year-old post-renal transplant man developed pain in the region of the allograft 4 days after transplantation. Contrast-enhanced CT scan revealed multiple small perfusion defects in the renal graft cortex. Multifocal renal cortical infarction was suspected. A [99mTc]Tc-DMSA SPECT/CT showed several small regions with decreased uptake. In addition, an [18F]PSMA-1007 PET/CT confirmed these uptake defects and revealed additional defects. The renal cortical infarctions presumably originated from intraoperative emboli emerging from the arterial anastomosis. Treatment with acetylsalicylic acid 100 mg led to favorable evolution of the renal function biochemically. Follow-up DMSA scintigraphy 3 months later showed resolution of the renal cortical defects.

Changing Threshold-Based Segmentation Has No Relevant Impact on Semi-Quantification in the Context of Structured Reporting for PSMA-PET/CT

Simple Summary

Molecular imaging of patients with prostate cancer is widely utilized. We aimed to determine whether changes in post-processing parameters, such as maximum intensity thresholds, can significantly alter results. We investigated 623 lesions that were positive on a molecular imaging scan and could not find any relevant impact on results when certain parameters were changed, in particular in lesions indicative for metastases of prostate cancer.

Abstract

Prostate-specific membrane antigen (PSMA)-directed positron emission tomography/computed tomography (PET/CT) is increasingly utilized for staging of men with prostate cancer (PC). To increase interpretive certainty, the standardized PSMA reporting and data system (RADS) has been proposed. Using PSMA-RADS, we characterized lesions in 18 patients imaged with ¹⁸F-PSMA-1007 PET/CT for primary staging and determined the stability of semi-quantitative parameters. Six hundred twenty-three lesions were categorized according to PSMA-RADS and manually segmented. In this context, PSMA-RADS-3A (soft-tissue) or -3B (bone) lesions are defined as being indeterminate for the presence of PC. For PMSA-RADS-4 and -5 lesions; however, PC is highly likely or almost certainly present [with further distinction based on absence (PSMA-RADS-4) or presence (PSMA-RADS-5) of correlative findings on CT]. Standardized uptake values (SUV_max, SUV_peak, SUV_mean) were recorded, and volumetric parameters [PSMA-derived tumor volume (PSMA-TV); total lesion PSMA (TL-PSMA)] were determined using different maximum intensity thresholds (MIT) (40 vs. 45 vs. 50%). SUV_max was significantly higher in PSMA-RADS-5 lesions compared to all other PSMA-RADS categories (p ≤ 0.0322). In particular, the clinically challenging PSMA-RADS-3A lesions showed significantly lower SUV_max and SUV_peak compared to the entire PSMA-RADS-4 or -5 cohort (p < 0.0001), while for PSMA-RADS-3B this only applies when compared to the entire PSMA-RADS-5 cohort (p < 0.0001), but not to the PSMA-RADS-4 cohort (SUV_max, p = 0.07; SUV_peak, p = 0.08). SUV_mean (p = 0.30) and TL-PSMA (p = 0.16) in PSMA-RADS-5 lesions were not influenced by changing the MIT, while PSMA-TV showed significant differences when comparing 40 vs. 50% MIT (p = 0.0066), which was driven by lymph nodes (p = 0.0239), but not bone lesions (p = 0.15). SUV_max was significantly higher in PSMA-RADS-5 lesions compared to all other PSMA-RADS categories in ¹⁸F-PSMA-1007 PET/CT. As such, the latter parameter may assist the interpreting molecular imaging specialist in assigning the correct PSMA-RADS score to sites of disease, thereby increasing diagnostic certainty. In addition, changes of the MIT in PSMA-RADS-5 lesions had no significant impact on SUV_mean and TL-PSMA in contrast to PSMA-TV.

Utility of 18F-rhPSMA-7.3 positron emission tomography for imaging of primary prostate cancer and pre-operative efficacy in N-staging of unfavorable intermediate to very high-risk patients validated by histopathology

¹⁸F-rhPSMA-7.3, the lead compound of a new class of radiohybrid prostate-specific membrane antigen (rhPSMA) ligands, is currently in phase III trials for prostate cancer (PCa) imaging. Here, we describe our experience in primary PCa staging. Methods: We retrospectively identified 279 patients with primary PCa who underwent ¹⁸F-rhPSMA-7.3 PET/CT (staging cohort). A subset of patients (83/279) subsequently underwent prostatectomy with lymph node (LN) dissection without prior treatment (efficacy cohort). Distribution of tumor lesions was determined for the staging cohort and stratified by National Comprehensive Cancer Network (NCCN) risk score. Involvement of pelvic LN was assessed retrospectively by 3 blinded independent central readers, and a majority rule was used for analysis. Standard surgical fields were rated on a five-point scale independently for PET and for morphological imaging. Results were compared to histopathological findings on a patient-, right vs. -left, and template-basis. Results: For the staging cohort ¹⁸F-rhPSMA-7.3 PET was positive in 275/279 (98.6%), 106/279 (38.0%), 46/279 (16.5%), 65/279 (23.3%) and 5/279 (1.8%) patients for local, pelvic nodal, extrapelvic nodal, metastatic bone, and visceral metastatic disease. In the efficacy cohort, LN metastases were present in 24/83 patients (29%), located in 48/420 (11%) resected templates and in 33/166 (19.9%) hemi-pelvic templates in histopathology. Based on majority vote results, the patient-level sensitivity, specificity and accuracy for pelvic nodal metastases were 66.7% (95%CI, 44.7-83.6%), 96.6% (95%CI, 87.3-99.4%) and 88.0% (95%CI, 78.5-93.8%) for ¹⁸F-rhPSMA-7.3 PET and 37.5% (95%CI, 19.6-59.2%), 91.5% (95%CI, 80.6-96.8%) and 75.9% (95%CI, 65.0-84.3%) for morphological imaging, respectively. ¹⁸F-rhPSMA-7.3 showed higher interobserver agreement than morphological imaging (patient-level Fleiss' κ=0.54; 95%CI, 0.47-0.62 vs. 0.24; 95%CI, 0.17-0.31). A mean standardized uptake value ratio of 6.6 (95%CI, 5.2-8.1) documented a high image contrast between local tumors and adjacent low urinary tracer retention. Conclusion: ¹⁸F-rhPSMA-7.3 PET offers superior diagnostic performance to morphological imaging for primary N-staging of newly diagnosed PCa, shows lower inter-reader variation, and offers good distinction between primary tumor and bladder background activity. With increasing NCCN risk group an increasing frequency of extra-prostatic tumor lesions was observed.

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

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

Accuracy of 68Ga-PSMA PET/CT for lymph node and bone primary staging in prostate cancer

PURPOSE

The aim of this study is to assess the accuracy of the ⁶⁸Ga-PSMA PET/CT for lymph nodes and bones in the primary stage of prostate cancer.

METHODS

A total of 126 patients who were submitted to ⁶⁸Ga-PSMA PET/CT from January 2016 to February 2019 for prostate cancer staging, detection of clinically significant lesions or active surveillance were included in this study. All studies were read by 2 experienced physicians (a nuclear physician and a radiologist). The reports were made in consensus and used by one of the authors to classify the exam in positive or negative. We evaluated presence of abnormal uptake in the prostate, lymph nodes, and bone. The reference standards were histopathological confirmation, confirmatory imaging exams and/or clinical follow-up showing lesion(s) regression after specific treatment, or typical osseous metastatic lesions and highly increased PSA levels.

RESULTS

Measurement of diagnostic performance indicated a sensitivity, specificity and accuracy of 75%, 96.3%, and 90.8%, respectively, for lymph node involvement, and 90.9%, 50%, and 76.5%, respectively for metastatic bone lesions.

CONCLUSION

This study showed high specificity and accuracy of ⁶⁸Ga-PSMA PET/CT for lymph node and bone involvement in prostate cancer staging.

Early molecular imaging response assessment based on determination of total viable tumor burden in [68Ga]Ga-PSMA-11 PET/CT independently predicts overall survival in [177Lu]Lu-PSMA-617 radioligand therapy

Purpose

In patients with metastatic castration-resistant prostate cancer (mCRPC) treated with prostate-specific membrane antigen-targeted radioligand therapy (PSMA-RLT), the predictive value of PSMA PET/CT-derived response is still under investigation. Early molecular imaging response based on total viable tumor burden and its association with overall survival (OS) was explored in this study.

Methods

Sixty-six mCRPC patients who received [¹⁷⁷Lu]Lu-PSMA-617 RLT within a prospective patient registry (REALITY Study, NCT04833517) were analyzed. Patients received a [⁶⁸Ga]Ga-PSMA-11 PET/CT scan before the first and after the second cycle of PSMA-RLT. Total lesion PSMA (TLP) was determined by semiautomatic whole-body tumor segmentation. Molecular imaging response was assessed by change in TLP and modified PERCIST criteria. Biochemical response was assessed using standard serum PSA and PCWG3 criteria. Both response assessment methods and additional baseline parameters were analyzed regarding their association with OS by univariate and multivariable analysis.

Results

By molecular imaging, 40/66 (60.6%) patients showed partial remission (PR), 19/66 (28.7%) stable disease (SD), and 7/66 (10.6%) progressive disease (PD). Biochemical response assessment revealed PR in 34/66 (51.5%) patients, SD in 20/66 (30.3%), and PD in 12/66 (18.2%). Response assessments were concordant in 49/66 (74.3%) cases. On univariate analysis, both molecular and biochemical response (p = 0.001 and 0.008, respectively) as well as two baseline characteristics (ALP and ECOG) were each significantly associated with OS. The median OS of patients showing molecular PR was 24.6 versus 10.7 months in the remaining patients (with SD or PD). On multivariable analysis molecular imaging response remained an independent predictor of OS (p = 0.002), eliminating biochemical response as insignificant (p = 0.515).

Conclusion

The new whole-body molecular imaging–derived biomarker, early change of total lesion PSMA (TLP), independently predicts overall survival in [¹⁷⁷Lu]Lu-PSMA-617 RLT in mCRPC, outperforming conventional PSA-based response assessment. TLP might be considered a more distinguished and advanced biomarker for monitoring PSMA-RLT over commonly used serum PSA.

Incremental Impact of [68 Ga]Ga-PSMA-11 PET/CT in Primary N and M Staging of Prostate Cancer Prior to Curative-Intent Surgery: a Prospective Clinical Trial in Comparison with mpMRI

Purpose

The main objective of this prospective study was to assess the value of gallium-68 prostate-specific membrane antigen ([⁶⁸ Ga]Ga-PSMA-11) positron emission tomography/computed tomography (PET/CT) in primary N and M staging of intermediate- and high-risk prostate cancer (PCa) patients before planned curative-intent radical prostatectomy (RPE) and extended pelvic lymph node dissection (ePLND). The second objective was to compare the [⁶⁸ Ga]Ga-PSMA-11 PET/CT findings with standard of care pelvic multi-parametric magnetic resonance imaging (mpMRI) in the detection of locoregional lymph node metastases and intraprostatic prostate cancer.

Procedures

A total of 81 patients (mean age: 64.5 years, baseline mean trigger PSA (tPSA) 15.4 ng/ml, ± 15.9) with biopsy proven PCa (24 intermediate- and 57 high risk) scheduled for RPE and ePLND were enrolled in this prospective study. In 52 patients [⁶⁸ Ga]Ga-PSMA-11 PET/CT, pelvic mpMRI, and RPE with ePLND have been performed. Clinical risk stratification and related biomarkers as well as Gleason score (GS) were recorded. The location of the index lesion (IL) was documented systematically for each modality using a standardized segmentation of the prostate in six segments. Distant bone and lymph node metastasis detected by [⁶⁸ Ga]Ga-PSMA-11 PET/CT were documented. [⁶⁸ Ga]Ga-PSMA-11 PET/CT findings were correlated with results of mpMRI and histopathology. A consensus of imaging, clinical and/or follow-up findings were used for determining the distant metastases, which were not verified by histopathology.

Results

In the patient cohort who underwent RPE, [⁶⁸ Ga]Ga-PSMA-11 PET/CT and mpMRI detected the IL in 86.5% and 98.1% of the patients, respectively. The median of the maximum standardized uptake value (SUVmax) in the intraprostatic IL was 12 (range, 4.7–67.8). Intraprostatic IL of the high-risk patients showed significantly higher SUVmax than those in patients with intermediate risk for distant metastases (n = 48; median: 17.84 vs. 8.77; p = 0.02).

In total 729 LN were removed by ePLND in 48 patients. The histopathology verified 26 pelvic lymph node metastases (pLNM) in 20.8% (10/48) of the patients, which have been correctly identified in 60% of the patients on [⁶⁸ Ga]Ga-PSMA-11 PET/CT, and in 50% on mpMRI. All but one pLNM had a maximum diameter below 10 mm.

Bone metastases (BM) and distant LNM (dLNM) were found in 17.3% of the patients on [⁶⁸ Ga]Ga-PSMA-11 PET/CT imaging. 39.0% of the [⁶⁸ Ga]Ga-PSMA-11 PET-positive BM showed no suspicious morphological correlation on CT.

Conclusion

[⁶⁸ Ga]Ga-PSMA-11 PET/CT shows high diagnostic performance for N and M staging of patients with intermediate- and high-risk prostate cancer and seems to be superior to pelvic mpMRI in the detection of locoregional lymph node metastases. A significant correlation was found between SUVmax of the intraprostatic index lesion and risk stratification based on tPSA level and GS. The results of this study emphasize again on the role of metabolic molecular imaging using specific tracers in selected patients, leading to tailored therapy approach.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11307-021-01650-9.

Response Assessment and Prediction of Progression-Free Survival by 68Ga-PSMA-11 PET/CT Based on Tumor-to-Liver Ratio (TLR) in Patients with mCRPC Undergoing 177Lu-PSMA-617 Radioligand Therapy

At present, little is known about the molecular imaging-based response assessment of prostate-specific membrane antigen (PSMA)-targeted radioligand therapy with ¹⁷⁷Lutetium (¹⁷⁷Lu-PSMA-617 RLT) in metastatic castration-resistant prostate cancer (mCRPC). Our study evaluated the response to RLT using both molecular imaging and biochemical response assessments, and their potential prediction of progression-free survival (PFS). Fifty-one consecutive patients given two cycles of RLT at 6-week intervals were analyzed retrospectively. ⁶⁸Ga-PSMA-11 PET/CT was obtained about 2 weeks prior to the first and 4–6 weeks after the second cycle. Molecular imaging-based response using SUV_peak and tumor-to-liver ratio (TLR) was determined by modified PERCIST criteria. ∆TLR and ∆SUV were significantly correlated with ∆PSA (p < 0.001, each). After a median follow-up of 49 months, the median PFS (95% CI) was 8.0 (5.9–10.1) months. In univariate analysis, responders showing partial remission (PR_PSA and PR_TLR) had significantly (p < 0.001, each) longer PFS (median: 10.5 and 9.3 months) than non-responders showing either stable or progressive disease (median: 4.0 and 3.5 months). Response assessment using SUV_peak failed to predict survival. In multivariable analysis, response assessment using TLR was independently associated with PFS (p < 0.001), as was good performance status (p = 0.002). Molecular imaging-based response assessment with ⁶⁸Ga-PSMA-11 PET/CT using normalization of the total lesion PSMA over healthy liver tissue uptake (TLR) could be an appropriate biomarker to monitor RLT in mCRPC patients and to predict progression-free survival (PFS) of this treatment modality.

PET Molecular Imaging: A Holistic Review of Current Practice and Emerging Perspectives for Diagnosis, Therapeutic Evaluation and Prognosis in Clinical Oncology

PET/CT molecular imaging has been imposed in clinical oncological practice over the past 20 years, driven by its two well-grounded foundations: quantification and radiolabeled molecular probe vectorization. From basic visual interpretation to more sophisticated full kinetic modeling, PET technology provides a unique opportunity to characterize various biological processes with different levels of analysis. In clinical practice, many efforts have been made during the last two decades to standardize image analyses at the international level, but advanced metrics are still under use in practice. In parallel, the integration of PET imaging with radionuclide therapy, also known as radiolabeled theranostics, has paved the way towards highly sensitive radionuclide-based precision medicine, with major breakthroughs emerging in neuroendocrine tumors and prostate cancer. PET imaging of tumor immunity and beyond is also emerging, emphasizing the unique capabilities of PET molecular imaging to constantly adapt to emerging oncological challenges. However, these new horizons face the growing complexity of multidimensional data. In the era of precision medicine, statistical and computer sciences are currently revolutionizing image-based decision making, paving the way for more holistic cancer molecular imaging analyses at the whole-body level.

The Establishment of New Thresholds for PLND-Validated Clinical Nomograms to Predict Non-Regional Lymph Node Metastases: Using 68Ga-PSMA PET/CT as References

Purpose

PLND (pelvic lymph node dissection)-validated nomograms are widely accepted clinical tools to determine the necessity of PLND by predicting the metastasis of lymph nodes (LNMs) in pelvic region. However, these nomograms are in lacking of a threshold to predict the metastasis of extrareolar lymph nodes beyond pelvic region, which is not suitable for PLND. The aim of this study is to evaluate a threshold can be set for current clinical PLND-validated nomograms to predict extrareolar LN metastases beyond pelvic region in high-risk prostate cancer patients, by using ⁶⁸Ga-PSMA PET/CT as a reference to determine LN metastases (LNMs).

Experimental Design

We performed a retrospective analysis of 57 high-risk treatment-naïve PC patients in a large tertiary care hospital in China who underwent ⁶⁸Ga-PSMA-617 PET/CT imaging. LNMs was detected by ⁶⁸Ga-PSMA-617 PET/CT and further determined by imaging follow-up after anti-androgen therapy. The pattern of LN metastatic spread of PC patients were evaluated and analyzed. The impact of ⁶⁸Ga-PSMA PET/CT on clinical decisions based on three clinical PLND-validated nomograms (Briganti, Memorial Sloan Kettering Cancer Center, Winter) were evaluated by a multidisciplinary prostate cancer therapy team. The diagnostic performance and the threshold of these nomograms in predicting extrareolar LNMs metastasis were evaluated via receiver operating characteristic (ROC) curve analysis.

Results

LNMs were observed in 49.1% of the patients by ⁶⁸Ga-PSMA PET/CT, among which 65.5% of LNMs were pelvic-regional and 34.5% of LNMs were observed in extrareolar sites (52.1% of these were located above the diaphragm). The Briganti, MSKCC and Winter nomograms showed that 70.2%-71.9% of the patients in this study need to receive ePLND according to the EAU and NCCN guidelines. The LN staging information obtained from ⁶⁸Ga-PSMA PET/CT would have led to changes of planned management in 70.2% of these patients, including therapy modality changes in 21.1% of the patients, which were mainly due to newly detected non-regional LNMs. The thresholds of nomograms to predict non-regional LNMs were between 64% and 75%. The PC patients with a score >64% in Briganti nomogram, a score >75% in MSKCC nomogram and a score >67% in Winter nomogram were more likely to have non-regional LNMs. The AUCs (Area under curves) of the clinical nomograms (Briganti, MSKCC and Winter) in predicting non-regional LNMs were 0.816, 0.830 and 0.793, respectively.

Conclusions

By using ⁶⁸Ga-PSMA PET/CT as reference of LNM, the PLND-validated clinical nomograms can not only predict regional LNMs, but also predict non-regional LNMs. The additional information from ⁶⁸Ga-PSMA PET/CT may provide added benefit to nomograms-based clinical decision-making in more than two-thirds of patients for reducing unnecessary PLND. We focused on that a threshold can be set for current clinical PLND-validated nomograms to predict extrareolar LN metastases with an AUC accuracy of about 80% after optimizing the simple nomograms which may help to improve the efficiency for PC therapy significantly in clinical practice.

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.