Head-to-Head Comparison of 68Ga-PSMA-11 with 18F-PSMA-1007 PET/CT in Staging Prostate Cancer Using Histopathology and Immunohistochemical Analysis as a Reference Standard

Radical prostatectomy without prostate biopsy based on a noninvasive diagnostic strategy: a prospective single-center study

BACKGROUND

Prostate biopsy is the most common approach for diagnosing prostate cancer (PCa); however, it has inherent limitations, such as the invasive procedure, postoperative complications, and false negative results. We aimed to provide a noninvasive diagnostic strategy for patients with highly suspected PCa and to evaluate the feasibility of performing biopsy-spared radical prostatectomy.

METHODS

This prospective study included a total of 57 patients between November 10, 2022, and December 1, 2023. All 57 patients underwent radical prostatectomy without prior prostate biopsy based on a noninvasive diagnostic strategy consisting of a diagnostic prediction model [comprised of the prostate imaging-reporting and data system (PI-RADS) score and prostate-specific antigen density (PSAD)] and the 18F-prostate-specific membrane antigen (PSMA)-1007 positron emission tomography (PET)/computed tomography (CT) examination. The primary endpoint was the positive predictive value (PPV) of clinically significant PCa [the International Society of Urological Pathology (ISUP) grade ≥2, Gleason score ≥3 + 4]. The secondary endpoints were a PPV of any-grade PCa (ISUP grade ≥ 1, Gleason score ≥3 + 3) and high-grade PCa (ISUP grade ≥3, Gleason score ≥4 + 3), and the false positive rate of the diagnostic strategy.

RESULTS

Of the 371 screened patients with clinically suspected PCa, 57 patients fulfilled the criteria and consented to participate in this study. The median PSAD level was 0.56 (0.42-0.82) ng/mL2; 13 (22.8%) patients were identified as having a PI-RADS score of 4, and 44 (77.2%) patients with a PI-RADS score of 5. The median SUVmax of 18F-PSMA-1007 PET/CT was 21.6 (15.8-33.0). For the 57 enrolled patients who received radical prostatectomy directly, the PPV of clinically significant PCa was 98.2% [56/57, 95% confidence interval (CI): 90.6-100%]. Only 1.8% (1/57, 95% CI: 0.0-9.4%) of patients were diagnosed with clinically insignificant PCa (ISUP grade = 1, Gleason score = 3 + 3). The PPV of any-grade PCa and high-grade PCa were 100% and 73.7% (42/57, 95% CI: 60.3-84.5%), respectively. No one had a false positive result.

CONCLUSIONS

We proposed a noninvasive diagnostic strategy consisting sequentially of a diagnostic prediction model and the 18F-PSMA-1007 PET/CT examination for diagnosing PCa. Despite some limitations, our initial findings suggest the potential feasibility of radical prostatectomy without prior prostate biopsy.

Prostate-Specific Membrane Antigen Positron Emission Tomography (PSMA-PET) in Initial Staging of Prostate Cancer Patients: The Beginning of a New Era

Background and Objectives: Prostate cancer (PCa) is a common disease, with a significant number of patients initially diagnosed with locoregional or distant metastases. This is why it is essential to have imaging tests with sufficient sensitivity and specificity. Given the recognized limitations of traditional imaging methods, PSMA-PET has emerged as a promising tool that may revolutionize the management of PCa. Material and Methods: We conducted a comprehensive literature review from August to October 2023 using databases and a review of key clinical guidelines on the topic, focusing on the sensitivity and specificity of PSMA-PET, its use in detecting lymph node metastases (LNm), its integration into nomograms, its comparison with conventional imaging and current guideline recommendations. Results: After considering the search strategy, as well as the inclusion and exclusion criteria, four articles and five guidelines were particularly considered in this review. Most of them suggest high specificity and limited sensitivity for 68Ga-PSMA-PET, with increased detection rates compared to conventional imaging modalities, especially in high-risk PCa patients. However, it cannot replace an extended pelvic lymph node dissection (ePLND) at this time. Conclusions: Although the enhanced sensitivity and specificity of PSMA-PET relative to conventional imaging modalities offers a more precise evaluation of disease extent, prospective studies demonstrating a survival benefit are currently lacking; therefore, caution is advised when making therapeutic decisions.

PSMA PET/CT for prostate cancer diagnosis: current applications and future directions

Prostate cancer (PCa) requires improved diagnostic strategies beyond conventional imaging. This review aimed to evaluate the role of prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) in diagnosing advanced PCa. The review analyzed the diagnostic performance of PSMA PET/CT in various clinical contexts, including locoregional staging, extracapsular extension (ECE), seminal vesicle invasion (SVI), pelvic lymph node metastases, distant metastases, and biochemical recurrence (BCR). Further, challenges such as PSMA-negative tumors, need for standardized protocols, and potential of emerging imaging targets (neurotensin receptor 1 and fibroblast activation proteins) were reviewed. The role of artificial intelligence (AI) and advancements in tracer development were explored. PSMA PET/CT demonstrated exceptional specificity for locoregional staging, ECE, and SVI while reducing unnecessary biopsies and optimizing biopsy strategies. The diagnostic accuracy for pelvic lymph node metastases was higher with PSMA PET/CT than with traditional methods, although sensitivity for micrometastasis detection remained challenging. For distant metastases, PSMA PET/CT outperformed bone scintigraphy (BS) and conventional imaging, particularly in identifying bone and atypical lesions. In BCR cases, PSMA PET/CT reliably detected recurrent lesions at low prostate-specific antigen levels, significantly influencing treatment strategies. The review findings indicate that PSMA PET/CT is a superior diagnostic tool for PCa due to its high specificity and accuracy. Despite limitations such as PSMA-negative tumors and sensitivity challenges, advancements in AI, novel imaging targets, and affordable tracer development hold promise for broader clinical adoption. This review underscores the transformative potential of PSMA PET/CT in PCa diagnosis and management, advocating for ongoing research and protocol standardization.

68Ga-FAPI and 18F-FAPI PET/CT for detection of nodal metastases prior radical cystectomy in high-risk urothelial carcinoma patients

INTRODUCTION

To determine the best therapeutic strategy for muscle-invasive bladder cancer (BC), the accuracy of lymph node staging is of paramount importance. However, diagnostic performance of conventional computed tomography in BC prior to radical cystectomy (RC) remains unsatisfactory. There is an increased interest in evaluating 18F-FAPI PET/CT for hybrid imaging due to their logistical advantages compared to [68Ga]Ga-based FAPI tracers in clinical routine. Recently, the potential diagnostic value of [68Ga]Ga-FAPI- 46 PET/CT was demonstrated in BC. Thus, we aimed to examine the diagnostic performance of [18F]F-FAPI- 74 and [68Ga]Ga-FAPI- 46 PET/CT for preoperative evaluation of locoregional lymph node metastases.

METHODS

Fifty-one patients underwent FAPI PET/CT with either [68Ga]Ga-FAPI- 46 (n = 23) or [18F]F-FAPI- 74 (n = 28) prior to RC and PLND. SUVmax, SUVmean and the ratio between the SUVmax of lymph nodes and the SUVmean of the background (SUVmax_lymph node/SUVmean_background) were assessed. Additionally, short axis diameter (SAD) for a representative lymph node were documented in each lymph node region (n = 123) and compared to histopathological findings. Each scan was interpreted visually and quantitatively. ROC-analyses were performed to determine cut-off values with highest diagnostic accuracy.

RESULTS

20/123 (16.3%) lymph node regions showed UC lymph node metastases. Histopathologically positive lymph nodes were associated with a significantly higher FAPI uptake compared to negative lymph nodes regarding SUVmax, SUVmean values and SUVmax_lymph node/SUVmean_background ratios. Visual analysis based on FAPI uptake showed a sensitivity and specificity, PPV and NPV of 63.6%, 95.8%, 77.7%, and 92.0% for [68Ga]Ga-FAPI- 46 and 55.5%, 98.1%, 83.3%, and 93.1% for [18F]F-FAPI- 74, respectively. ROC analysis revealed an optimal cut-off for SUVmax, SUVmean and SUVmax_lymph node/SUVmean_background of 1.35, 1.20 and 5.95 for [68Ga]Ga-FAPI- 46 and 1.55, 1.25 and 4.15 for [18F]F-FAPI- 74 to discriminate between histopathologically proven lymph node metastases and non-malignant lymph nodes resulting for example using SUVmax in a sensitivity and specificity, PPV and NPV of 81.8%, 89.5%, 64.2%, 95.5% for [68Ga]Ga-FAPI- 46 and 100%, 81.8%, 47.3%, 100% for [18F]F-FAPI- 74, respectively. CT visual analysis of locoregional lymph nodes showed a sensitivity, specificity, PPV and NPV of 30.0%, 97.0%, 66.6% and 87.7%, respectively. ROC analysis regarding SAD revealed a cutoff at 0.8 cm with a sensitivity, specificity, PPV and NPV of 75.0%, 84.4%, 48.3%, 94.5%, respectively.

CONCLUSION

Overall, FAPI PET imaging shows a significantly higher sensitivity than CT analysis for detection of locoregional lymph node metastases in UC. [18F]F-FAPI- 74 demonstrates a comparable diagnostic performance compared to [68Ga]Ga-FAPI- 46. Of note, the quantitative analysis with a pre-defined SUVmax as well as SUVmean values, and SUVmax_lymph node/SUVmean_background ratio-based cut-offs provided a higher sensitivity compared to visual assessment.

Mapping the knowledge landscape of the PET/MR domain: a multidimensional bibliometric analysis

OBJECTIVE

This study aims to conduct a bibliometric analysis to explore research trends, collaboration patterns, and emerging themes in the PET/MR field based on published literature from 2010 to 2024.

METHODS

A detailed literature search was performed using the Web of Science Core Collection (WoSCC) database with keywords related to PET/MR. A total of 4,349 publications were retrieved and analyzed using various bibliometric tools, including VOSviewer and CiteSpace.

RESULTS

The analysis revealed an initial increase in PET/MR publications, peaking at 495 in 2021, followed by a slight decline. The USA, Germany, and China were the most prolific countries, with the USA demonstrating strong collaborative networks. Key institutions included the Stanford University, Technical University of Munich and University of Duisburg-Essen. Prominent authors were primarily from Germany, with significant contributions from University Hospital Essen. Major journals in the field included the European Journal of Nuclear Medicine, Journal of Nuclear Medicine, and Physics in Medicine and Biology. Emerging research areas focused on oncology, neurological disorders, and cardiovascular diseases, with keywords such as "prostate cancer," "Alzheimer's disease," and "breast cancer" showing high research activity. Recent trends also highlight the growing integration of AI, particularly deep learning, to improve imaging reconstruction and diagnostic accuracy.

CONCLUSION

The findings emphasize the need for continuous investment, strategic planning, and technological innovations to expand PET/MR's clinical applications. Future research should focus on optimizing imaging techniques, fostering international collaborations, and integrating emerging technologies like artificial intelligence to enhance PET/MR's diagnostic and therapeutic potential in precision medicine.

Prospective comparison of 18F-PSMA-1007 PET/CT and MRI with histopathology as the reference standard for intraprostatic tumour detection and T-staging of high-risk prostate cancer

PURPOSE

To prospectively compare the ability of 18F-PSMA-1007 PET/CT and whole-body MRI (WBMRI) with DWI to detect prostate cancer (PCa) lesions and assess their local stage. Additionally, to evaluate the correlation between PSMA uptake on PET/CT and PSMA expression as assessed by immunohistochemistry.

METHODS

Men with newly diagnosed unfavourable intermediate or high-risk PCa underwent 18F-PSMA-1007 PET/CT and WBMRI with DWI before robot-assisted laparoscopic prostatectomy. Diagnostic accuracy for intraprostatic tumour localization, seminal vesicle invasion (SVI), and extraprostatic extension (EPE) was evaluated using whole-mount prostatectomy specimens as the reference standard. SUVmax was compared with immunohistochemical PSMA staining intensity quantified using QuPath software.

RESULTS

19 patients with 39 intraprostatic lesions in histopathology were included. The overall lesion detection rates for PET/CT were 84.6% and 82.1% for two independent readers, compared to 74.4% and 46.2% for MRI readers. The detection rates of index lesions were 94.7% for PET/CT and 74.0-84.0% for MRI, whereas those of non-index lesions were 70.0-75.0% for PET/CT and 20.0-65.0% for MRI. For detecting EPE, AUC values were 0.500-0.591 for PET/CT and 0.648-0.682 for MRI. For detecting SVI, AUC values ranged from 0.629 to 0.700 across both modalities. SUVmax showed a weak correlation with immunohistochemical expression of PSMA multiplied by lesion diameter (Spearman's ρ = 0.427, p = 0.013). Lesion diameters measured using 30% and 40% of SUVmax, as well as prostate SUVbackground x2, showed the closest agreement with histopathological measurements.

CONCLUSION

18F-PSMA-1007 PET/CT demonstrated high sensitivity in localizing intraprostatic carcinoma lesions but seemed inferior to WBMRI in detecting EPE. PSMA uptake appears to depend on both PSMA expression and lesion size. These findings highlight the complementary roles of PET/CT and MRI in the detection and tumor staging of PCa.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov ID: NCT03537391. Registered 25 May 2018.

Phase I study of [68Ga]Ga-HX01 for targeting integrin αvβ3 and CD13 in healthy and malignancy subjects

PURPOSE

Noninvasive angiogenesis visualization is essential for evaluating tumor proliferation, progression, invasion, and metastasis. This study aimed to translate the heterodimeric PET tracer [68Ga]Ga-HX01, which targets integrin αvβ3 and CD13 in neovascularization, into phase I clinical study.

METHODS

This study enrolled 12 healthy volunteers (phase Ia) and 10 patients with malignant tumors (phase Ib). The subjects in phase Ia were divided into low-dose (0.05 mCi/kg) and high-dose (0.1 mCi/kg) groups. For phase Ia subjects, PET/CT images, blood and urine samples were collected to analyze the biodistribution, pharmacokinetics, radiation dosimetry, and safety of [68Ga]Ga-HX01. For phase Ib patients, PET/MR scans were performed at 30 ± 5 and 60 ± 5 min after injection. The safety and preliminary diagnostic value of [68Ga]Ga-HX01 were assessed.

RESULTS

In phase Ia study, [68Ga]Ga-HX01 was distributed and metabolized similarly in two dosage groups as the highest accumulations in kidneys and urine. It possessed quick renal excretion and blood clearance with an elimination half-life (T1/2) of 28.92 ± 3.97 min. The total effective dose was 2.14 × 10- 2 mSv/MBq. In phase Ib study, [68Ga]Ga-HX01 clearly detected the lesions per patient, and found a total of 59 lesions with varying uptake levels. For safety evaluation, no serious adverse events were observed during the examination.

CONCLUSION

[68Ga]Ga-HX01 has proved to be a translational radiopharmaceutical with reliable security, favorable pharmacokinetics, and the ability to visualize tumors. The preliminary results in malignancy patients warrant further investigation of [68Ga]Ga-HX01 in monitoring antiangiogenic therapy of patients with malignancies.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT06416774. Registered 11 May, 2024.

Enhanced radiotheranostic targeting of integrin α5β1 with PEGylation-enabled peptide multidisplay platform (PEGibody): A strategy for prolonged tumor retention with fast blood clearance

Peptide-based radiopharmaceuticals targeting integrin α5β1 show promise for precise tumor diagnosis and treatment. However, current peptide-based radioligands that target α5β1 demonstrate inadequate in vivo performance owing to limited tumor retention. The use of PEGylation to enhance the tumor retention of radiopharmaceuticals by prolonging blood circulation time poses a risk of increased blood toxicity. Therefore, a PEGylation strategy that boosts tumor retention while minimizing blood circulation time is urgently needed. Here, we developed a PEGylation-enabled peptide multidisplay platform (PEGibody) for PR_b, an α5β1 targeting peptide. PEGibody generation involved PEGylation and self-assembly. [64Cu]QM-2303 PEGibodies displayed spherical nanoparticles ranging from 100 to 200 nm in diameter. Compared with non-PEGylated radioligands, [64Cu]QM-2303 demonstrated enhanced tumor retention time due to increased binding affinity and stability. Importantly, the biodistribution analysis confirmed rapid clearance of [64Cu]QM-2303 from the bloodstream. Administration of a single dose of [177Lu]QM-2303 led to robust antitumor efficacy. Furthermore, [64Cu]/[177Lu]QM-2303 exhibited low hematological and organ toxicity in both healthy and tumor-bearing mice. Therefore, this study presents a PEGibody-based radiotheranostic approach that enhances tumor retention time and provides long-lasting antitumor effects without prolonging blood circulation lifetime. The PEGibody-based radiopharmaceutical [64Cu]/[177Lu]QM-2303 shows great potential for positron emission tomography imaging-guided targeted radionuclide therapy for α5β1-overexpressing tumors.

Which PSMA PET/CT interpretation criteria most effectively diagnose prostate cancer? a retrospective cohort study

BACKGROUND

PSMA PET/CT emerges as a pivotal technology in the diagnostic landscape of prostate cancer (PCa). It offers a suite of imaging interpretation criteria, notably the maximum standardized uptake value (SUVmax), the molecular imaging prostate-specific membrane antigen score (miPSMA score), and the PSMA reporting and data system (PSMA-RADS). Identifying the most valuable criteria for diagnosing PCa and standardizing imaging interpretation across various tracers is an unresolved question. Our study endeavors to pinpoint the most optimal criteria to enhance the precision of PCa diagnosis, encompassing clinically significant PCa (csPCa), by evaluating the consistency and diagnostic accuracy of these three criteria using two [18F]-labeled PSMA tracers.

METHOD

This retrospective analysis spans a five-year period, focusing on patients with clinically suspected or newly diagnosed, treatment-naïve PCa who underwent 18F-PSMA PET/CT. The study is bifurcated into two segments: 1.A direct comparison assessing the consistency in SUVmax, miPSMA scores, and PSMA-RADS among PSMA PET/CT tracers ([18F]DCFPyL and [18F]PSMA-1007) for prostate foci in 24 patients. 2. An analysis of the diagnostic accuracy of these three criteria for both PCa and csPCa across 55 [18F]DCFPyL and 65 [18F]PSMA-1007 PET/CT scans, respectively.

RESULTS

1.Our head-to-head study reveals that SUVmax and miPSMA score exhibit near-perfect consistency, with PSMA-RADS demonstrating substantial consistency. 2. The diagnostic accuracy ranking, considering both PCa and csPCa, stands as miPSMA score ≈ SUVmax > PSMA-RADS for [18F]DCFPyL PET/CT, contrasting with miPSMA score > SUVmax ≈ PSMA-RADS for [18F]PSMA-1007 PET/CT.

CONCLUSION

The miPSMA score outperforms SUVmax and PSMA-RADS in terms of inter-tracer consistency and diagnostic accuracy for the detection of PCa, including csPCa, when comparing [18F]DCFPyL and [18F]PSMA-1007 PET/CT scans. This underscores the miPSMA score's potential as a robust criterion for PCa and csPCa diagnosis, holding substantial promise for refining clinical decision-making and patient management strategies.

CLINICAL TRIAL NUMBER

not applicable.

Advancements in molecular imaging probes for precision diagnosis and treatment of prostate cancer

Prostate cancer is the second most common cancer in men, accounting for 14.1% of new cancer cases in 2020. The aggressiveness of prostate cancer is highly variable, depending on its grade and stage at the time of diagnosis. Despite recent advances in prostate cancer treatment, some patients still experience recurrence or even progression after undergoing radical treatment. Accurate initial staging and monitoring for recurrence determine patient management, which in turn affect patient prognosis and survival. Classical imaging has limitations in the diagnosis and treatment of prostate cancer, but the use of novel molecular probes has improved the detection rate, specificity, and accuracy of prostate cancer detection. Molecular probe-based imaging modalities allow the visualization and quantitative measurement of biological processes at the molecular and cellular levels in living systems. An increased understanding of tumor biology of prostate cancer and the discovery of new tumor biomarkers have allowed the exploration of additional molecular probe targets. The development of novel ligands and advances in nano-based delivery technologies have accelerated the research and development of molecular probes. Here, we summarize the use of molecular probes in positron emission tomography (PET), single-photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), optical imaging, and ultrasound imaging, and provide a brief overview of important target molecules in prostate cancer.

PSMA-Targeted Intracellular Self-Assembled Probe for Enhanced PET Imaging

Positron-emission tomography (PET) offers high sensitivity for cancer diagnosis. However, small-molecule-based probes often exhibit insufficient accumulation in tumor sites, while nanoparticle-based agents typically have limited delivery efficiency. To address this challenge, this study proposes a novel PET imaging probe, 68Ga-CBT-PSMA, designed for prostate cancer. This probe integrates an intracellular self-assembly strategy to enhance PET imaging signals and significantly improve the signal-to-noise ratio. The glutamate-urea-based prostate-specific membrane antigen (PSMA)-targeting motif enables specific recognition of prostate cancer cells and enhances cellular uptake; then the self-assembly process induced by glutathione reduction effectively accumulates the probe within tumor cells, thereby amplifying PET imaging signals. This approach not only enhances signal intensity and resolution but also facilitates precise cancer localization and diagnosis, offering new avenues for advancing cancer diagnostic techniques.

A Personalized Approach for Oligometastatic Prostate Cancer: Current Understanding and Future Directions

Oligometastatic prostate cancer (OMPC) represents an intermediate state in the progression from localized disease to widespread metastasis when the radiographically significant sites are limited in number and location. With no clear consensus on a definition, its diagnostic significance and associated optimal therapeutic approach remain controversial, posing a significant challenge for clinicians. The current standard of care for metastatic disease is to start systemic therapy; however, active surveillance and targeted radiotherapy have become attractive options to mitigate the long-term effects of androgen deprivation therapy (ADT). Furthermore, evolving biomarker methodologies may further define optimal treatment selection. In this review, we summarize the current understanding that guides the treatment of OMPC, with a focus on how host response can be an important contributing factor. Evolving scientific understanding and clinical development will continue to shape the landscape of treatment strategies for this distinct disease state.

Radiopharmaceuticals and their applications in medicine

Radiopharmaceuticals involve the local delivery of radionuclides to targeted lesions for the diagnosis and treatment of multiple diseases. Radiopharmaceutical therapy, which directly causes systematic and irreparable damage to targeted cells, has attracted increasing attention in the treatment of refractory diseases that are not sensitive to current therapies. As the Food and Drug Administration (FDA) approvals of [177Lu]Lu-DOTA-TATE, [177Lu]Lu-PSMA-617 and their complementary diagnostic agents, namely, [68Ga]Ga-DOTA-TATE and [68Ga]Ga-PSMA-11, targeted radiopharmaceutical-based theranostics (radiotheranostics) are being increasingly implemented in clinical practice in oncology, which lead to a new era of radiopharmaceuticals. The new generation of radiopharmaceuticals utilizes a targeting vector to achieve the accurate delivery of radionuclides to lesions and avoid off-target deposition, making it possible to improve the efficiency and biosafety of tumour diagnosis and therapy. Numerous studies have focused on developing novel radiopharmaceuticals targeting a broader range of disease targets, demonstrating remarkable in vivo performance. These include high tumor uptake, prolonged retention time, and favorable pharmacokinetic properties that align with clinical standards. While radiotheranostics have been widely applied in tumor diagnosis and therapy, their applications are now expanding to neurodegenerative diseases, cardiovascular diseases, and inflammation. Furthermore, radiotheranostic-empowered precision medicine is revolutionizing the cancer treatment paradigm. Diagnostic radiopharmaceuticals play a pivotal role in patient stratification and treatment planning, leading to improved therapeutic outcomes in targeted radionuclide therapy. This review offers a comprehensive overview of the evolution of radiopharmaceuticals, including both FDA-approved and clinically investigated agents, and explores the mechanisms of cell death induced by radiopharmaceuticals. It emphasizes the significance and future prospects of theranostic-based radiopharmaceuticals in advancing precision medicine.

Biological determinants of PSMA expression, regulation and heterogeneity in prostate cancer

Prostate-specific membrane antigen (PSMA) is an important cell-surface imaging biomarker and therapeutic target in prostate cancer. The PSMA-targeted theranostic 177Lu-PSMA-617 was approved in 2022 for men with PSMA-PET-positive metastatic castration-resistant prostate cancer. However, not all patients respond to PSMA-radioligand therapy, in part owing to the heterogeneity of PSMA expression in the tumour. The PSMA regulatory network is composed of a PSMA transcription complex, an upstream enhancer that loops to the FOLH1 (PSMA) gene promoter, intergenic enhancers and differentially methylated regions. Our understanding of the PSMA regulatory network and the mechanisms underlying PSMA suppression is evolving. Clinically, molecular imaging provides a unique window into PSMA dynamics that occur on therapy and with disease progression, although challenges arise owing to the limited resolution of PET. PSMA regulation and heterogeneity - including intertumoural and inter-patient heterogeneity, temporal changes, lineage dynamics and the tumour microenvironment - affect PSMA theranostics. PSMA response and resistance to radioligand therapy are mediated by a number of potential mechanisms, and complementary biomarkers beyond PSMA are under development. Understanding the biological determinants of cell surface target regulation and heterogeneity can inform precision medicine approaches to PSMA theranostics as well as other emerging therapies.

Diagnostic value of 18F-PSMA-1007 PET/CT for predicting the pathological grade of prostate cancer

This study was designed to evaluate the diagnostic efficacy of relevant parameters of 18F-prostate-specific membrane antigen (PSMA)-1007 PET/CT in predicting the pathological grade of primary prostate cancer. Briefly, a prospective analysis was performed on 53 patients diagnosed with prostate cancer by systematic puncture biopsy, followed by 18F-PSMA-1007 PET/CT examination prior to treatment within 10 d. The patients were grouped in accordance with the Gleason grading system revised by the International Association of Urology Pathology (ISUP). They were divided into high-grade group (ISUP 4-5 group) and low-grade group (ISUP 1-3 group). The differences in maximum standardized uptake value (SUVmax), tumor-to-background ratio (TBR), intraprostatic PSMA-derived tumor volume (iPSMA-TV), and intraprostatic total lesion PSMA (iTL-PSMA) between the high- and low-grade group were statistically significant (p < .001). No significant difference was found for mean standardized uptake value (SUVmean) between the high- and low-grade groups (Z =  -1.131, p = .258). Besides, binary multivariate logistic regression analysis showed that only iPSMA-TV and iTL-PSMA were independent predictors of the pathological grading, for which the odds ratios were 18.821 [95% confidence interval (CI): 2.040-173.614, p = .010] and 0.758 (95% CI: 0.613-0.938, p = .011), respectively. The area under the ROC of this regression model was 0.983 (95% CI: 0.958-1.00, p < .001). Only iTL-PSMA was a significant parameter for distinguishing ISUP-4 and ISUP-5 groups (Z =  -2.043, p = .041). In a nutshell, 18F-PSMA-1007 PET/CT has good application value in predicting the histopathological grade of primary prostate cancer. Three-dimensional volume metabolism parameters iPSMA-TV and iTL-PSMA were found to be independent predictors for pathological grade.

The association of quantitative PSMA PET parameters with pathologic ISUP grade: an international multicenter analysis

PURPOSE

To assess if PSMA PET quantitative parameters are associated with pathologic ISUP grade group (GG) and upgrading/downgrading.

METHODS

PCa patients undergoing radical prostatectomy with or without pelvic lymph node dissection staged with preoperative PSMA PET at seven referral centres worldwide were evaluated. PSMA PET parameters which included SUVmax, PSMAvolume, and total PSMA accumulation (PSMAtotal) were collected. Multivariable logistic regression evaluated the association between PSMA PET quantified parameters and surgical ISUP GG. Decision-tree analysis was performed to identify discriminative thresholds for all three parameters related to the five ISUP GGs The ROC-derived AUC was used to determine whether the inclusion of PSMA quantified parameters improved the ability of multivariable models to predict ISUP GG ≥ 4.

RESULTS

A total of 605 patients were included. Overall, 2%, 37%, 37%, 10% and 13% patients had pathologic ISUP GG1, 2, 3, 4, and 5, respectively. At multivariable analyses, all three parameters SUVmax, PSMAvolume and PSMAtotal were associated with GG ≥ 4 at surgical pathology after accounting for PSA and clinical T stage based on DRE, hospital and radioligand (all p < 0.05). Addition of all three parameters significantly improved the discrimination of clinical models in predicting GG ≥ 4 from 68% (95%CI 63 - 74) to 74% (95%CI 69 - 79) for SUVmax, 72% (95%CI 67 - 76) for PSMAvolume, 74% (70 - 79) for PSMAtotal and 75% (95%CI 71 - 80) when all parameters were included (all p < 0.05). Decision-tree analysis resulted in thresholds that discriminate between GG (SUVmax 0-6.5, 6.5-15, 15-28, > 28, PSMAvol 0-2, 2-9, 9-20 and > 20 and PSMAtotal 0-12, 12-98 and > 98). PSMAvolume was significantly associated with GG upgrading (OR 1.03 95%CI 1.01 - 1.05). In patients with biopsy GG1-3, PSMAvolume ≥ 2 was significantly associated with higher odds for upgrading to ISUP GG ≥ 4, compared to PSMAvolume < 2 (OR 6.36, 95%CI 1.47 - 27.6).

CONCLUSION

Quantitative PSMA PET parameters are associated with surgical ISUP GG and upgrading. We propose clinically relevant thresholds of these parameters which can improve in PCa risk stratification in daily clinical practice.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Target Volume Optimization for Localized Prostate Cancer

PURPOSE

To provide a comprehensive review of the means by which to optimize target volume definition for the purposes of treatment planning for patients with intact prostate cancer with a specific emphasis on focal boost volume definition.

METHODS

Here we conduct a narrative review of the available literature summarizing the current state of knowledge on optimizing target volume definition for the treatment of localized prostate cancer.

RESULTS

Historically, the treatment of prostate cancer included a uniform prescription dose administered to the entire prostate with or without coverage of all or part of the seminal vesicles. The development of prostate magnetic resonance imaging (MRI) and positron emission tomography (PET) using prostate-specific radiotracers has ushered in an era in which radiation oncologists are able to localize and focally dose-escalate high-risk volumes in the prostate gland. Recent phase 3 data has demonstrated that incorporating focal dose escalation to high-risk subvolumes of the prostate improves biochemical control without significantly increasing toxicity. Still, several fundamental questions remain regarding the optimal target volume definition and prescription strategy to implement this technique. Given the remaining uncertainty, a knowledge of the pathological correlates of radiographic findings and the anatomic patterns of tumor spread may help inform clinical judgement for the definition of clinical target volumes.

CONCLUSION

Advanced imaging has the ability to improve outcomes for patients with prostate cancer in multiple ways, including by enabling focal dose escalation to high-risk subvolumes. However, many questions remain regarding the optimal target volume definition and prescription strategy to implement this practice, and key knowledge gaps remain. A detailed understanding of the pathological correlates of radiographic findings and the patterns of local tumor spread may help inform clinical judgement for target volume definition given the current state of uncertainty.

Expanding Role for Gallium-68 PET Imaging in Oncology

Gallium-68 has gained substantial momentum since 2003 as a versatile radiometal that is extremely useful for application in the development of novel oncology targeting diagnostic radiopharmaceuticals. It is available through both generator produced radioactivity and via cyclotron production methods and can therefore be implemented in either small- or large-scale production facilities. It can also be implemented within different spectrum of infrastructure settings with relative ease. Whilst many of the radiopharmaceuticals are being development and investigated, which is summarized in this manuscript, [68Ga]Ga-SSTR2 and [68Ga]Ga-PSMA has prominence in current clinical guidelines. The novel tracer [68Ga]Ga-FAPi has also gained significant interest in the clinical context. A comparison of the labelling strategies followed to incorporate gallium-68 and fluorine-18 into the same molecular targeting constructs clearly demonstrate that gallium-68 complexation is the most convenient approach. Recently, cold kit based starting products are available to make the small-scale production of gallium-68 radiopharmaceuticals even more efficient when combined with generator produced gallium-68. The regulatory aspects is currently changing to support the implementation of gallium-68 and other diagnostic radiopharmaceuticals, simplifying the translation towards clinical use. Overall, the development of gallium-68 based radiopharmaceuticals is not only rapidly changing the landscape of diagnosis in oncology, but this growth also promotes innovation and progress in new applications of therapeutic radiometals such as lutetium-177 and actinium-225.

Focal Unspecific Bone Uptake on [18F]PSMA-1007 PET: Evaluation Analog PROMISE Criteria and Validation via PET/CT Follow-Up

Background: Focal unspecific bone uptake (UBU) is common in [18F]PSMA-1007 PET/CT, yet its clinical significance remains unclear, causing uncertainty in treatment decisions. Material and Methods: We retrospectively analyzed 99 prostate cancer patients (age 69 ± 7) who underwent [18F]PSMA-1007 PET/CT scans (3 MBq/kg; uptake time 70 ± 14 min) for staging and follow-up (after 13.0 ± 7.2 months). Semiquantitative assessment using the miPSMA score, analogous to the PROMISE criteria, evaluated the prevalence of UBU and bone metastases. Results: In the initial PET/CT scan, 56 patients had 230 lesions classified as UBU. A total of 19 patients were found to have bone metastases and UBU, while 24 patients had no focal bone uptake. UBU distribution was as follows: ribs (50%), spine (30%), pelvis (15%), and other sites (5%). There were no significant differences in age, Gleason score, injected tracer dose, uptake time, SUVpeak of UBU, or SUVmean in the spleen and parotid gland between patients with and without UBU. Follow-up showed stable miPSMA-score and CT appearance in 44/56 patients with UBU (79%), minor changes in 5/56 patients (8%), and new bone metastases in 7/56 patients (12%). Patient-specific analysis indicated at least one bone metastasis initially classified as UBU in 3/56 patients (5%) and new bone metastases in 4/56 patients (7%). In total, 4 of the 24 patients (17%) without initial focal uptake developed osseous metastases at follow-up. Conclusions: No significant differences were found between patients with or without UBU. Only a small portion of UBU (2%) evolved into metastases, a lower rate than the development of new osseous metastases, which appears to be independent of UBU.

[18F]AlF-PSMA-11 PET in diagnosing prostate cancer: a head-to-head comparison with [68Ga]Ga-PSMA-11 PET and an exploration of dual-phase scanning

PURPOSE

To evaluate the physiological distribution and tumour detection ability of [18F]AlF-PSMA-11 positron emission tomography (PET) dual-phase scans in patients with prostate cancer (PCa).

METHODS

As a retrospective study, clinical and PET data of PCa patients who underwent dual-phase [18F]AlF-PSMA-11 PET of routine scan (45-50 min) and delayed scan (120 min) from November 2020 to June 2021 were collected, and physiological and pathological regions of interest were quantified to determine the time-dependent maximum standardized uptake value (SUVmax) of [18F]AlF-PSMA-11. Part of the above subjects who underwent [68Ga]Ga-PSMA-11 PET in the following 6 months were included in a head-to-head comparison. The difference with a p-value < 0.05 was defined as statistical significance. Diagnosis accuracy of primary and metastatic lesions was measured referring to the surgical findings, pathology, and follow-up imaging.

RESULTS

[68Ga]Ga-PSMA-11 and [18F]AlF-PSMA-11 were of the comparable uptake in glands in head, but the latter was of a significant lower distribution in liver and spleen. For the 25 patients initially diagnosed with prostate cancer and 3 patients with biochemical recurrence after radical surgery, the SUVmax of the primary lesions, lacrimal glands, parotid glands and submandibular glands was higher at 120 min compared to that at 45-50 min, but not a significant difference. SUVmax of the liver, spleen and bladder decreased significantly at 120 min, but the bladder SUVmax remained higher than that of primary lesions. SUVmax of the kidneys and centrum was the same in dual-phase scans. For the 31 primary lesions detected in [18F]AlF-PSMA-11 PET, both the SUVmax of the two phases kept the positive correlation with PSA, Gleason score and initial risk stratification. For the 39 distant metastatic lesions, 94.87% accuracy of routine scan and 100% accuracy of delayed scan were acquired, and 7.14% patients (2/28) benefited from the dual-phase [18F]AlF-PSMA-11 scans that revealed novel information on metastatic lesions compared to the routine scan.

CONCLUSION

[18F]AlF-PSMA-11 PET expanded the time window and further decreased metabolic background of [68Ga]Ga-PSMA-11 PET. The dual-phase scan of [18F]AlF-PSMA-11 PET can benefit prostate cancer diagnosis via providing more PSMA-specific information.

Imaging and therapy in prostate cancer using prostate specific membrane antigen radioligands

Prostate specific membrane antigen (PSMA) directed PET imaging has rapidly transformed prostate cancer workup over the past decade and paved the way for a theranostic approach using 177Lu-labelled PSMA radioligand therapy (RLT). This review gives an overview of the underlying principles behind PSMA as a target; the current use of PSMA PET in prostate cancer imaging and benefits compared to conventional imaging; and therapeutic applications including optimisation of patient selection. It also explores the evidence base of PSMA PET for other indications not in routine clinical use and the future of PSMA-directed RLT.

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.

Prostate Cancer Radioligand Therapy: Beta-labeled Radiopharmaceuticals

Prostate cancer is the most common malignancy in men worldwide, with an estimated 174,650 new cases per year in the United States, and the second cancer-related cause of death, after lung cancer, with 31,620 deaths per year. While the 5 year survival rate for prostate cancer in patients without metastatic spread is nearly 100%, those with distant metastases have 5 year survival rates of approximately 30%. Initial diagnosis and assessment are based on PSA levels, Gleason score (derived from prostate biopsy), and advanced imaging modalities, including prostate MR imaging and PSMA-PET/computed tomography in patients with high-risk features.

Advances in Prostate Cancer Biomarkers and Probes

Prostate cancer is one of the most prevalent malignant tumors in men worldwide, and early diagnosis is essential to improve patient survival. This review provides a comprehensive discussion of recent advances in prostate cancer biomarkers, including molecular, cellular, and exosomal biomarkers. The potential of various biomarkers such as gene fusions (TMPRSS2-ERG), noncoding RNAs (SNHG12), proteins (PSA, PSMA, AR), and circulating tumor cells (CTCs) in the diagnosis, prognosis, and targeted therapies of prostate cancer is emphasized. In addition, this review systematically explores how multi-omics data and artificial intelligence technologies can be used for biomarker discovery and personalized medicine applications. In addition, this review provides insights into the development of specific probes, including fluorescent, electrochemical, and radionuclide probes, for sensitive and accurate detection of prostate cancer biomarkers. In conclusion, this review provides a comprehensive overview of the status and future directions of prostate cancer biomarker research, emphasizing the potential for precision diagnosis and targeted therapy.

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.

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

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

Imaging at the nexus: how state of the art imaging techniques can enhance our understanding of cancer and fibrosis

Both cancer and fibrosis are diseases involving dysregulation of cell signaling pathways resulting in an altered cellular microenvironment which ultimately leads to progression of the condition. The two disease entities share common molecular pathophysiology and recent research has illuminated the how each promotes the other. Multiple imaging techniques have been developed to aid in the early and accurate diagnosis of each disease, and given the commonalities between the pathophysiology of the conditions, advances in imaging one disease have opened new avenues to study the other. Here, we detail the most up-to-date advances in imaging techniques for each disease and how they have crossed over to improve detection and monitoring of the other. We explore techniques in positron emission tomography (PET), magnetic resonance imaging (MRI), second generation harmonic Imaging (SGHI), ultrasound (US), radiomics, and artificial intelligence (AI). A new diagnostic imaging tool in PET/computed tomography (CT) is the use of radiolabeled fibroblast activation protein inhibitor (FAPI). SGHI uses high-frequency sound waves to penetrate deeper into the tissue, providing a more detailed view of the tumor microenvironment. Artificial intelligence with the aid of advanced deep learning (DL) algorithms has been highly effective in training computer systems to diagnose and classify neoplastic lesions in multiple organs. Ultimately, advancing imaging techniques in cancer and fibrosis can lead to significantly more timely and accurate diagnoses of both diseases resulting in better patient outcomes.

Intrahepatic cholangiocarcinoma detected on 18F-PSMA-1007 PET/MR imaging in a prostate cancer patient: a case report and literature review

Radionuclide probes-targeted prostate-specific membrane antigen (PSMA) is used in diagnosis and treatment of prostate cancer (PCa). Recent studies have shown that PSMA is expressed in the tumor neovascular endothelium, such as in malignant liver tumors. We report a case of PCa with incidental intrahepatic cholangiocarcinoma (ICC) detection using 18F-PSMA-1007 and 18F-fluorodeoxyglucose (FDG) positron emission topography (PET)/MRI.18F-PSMA-1007 PET/MRI of our patient with PCa showed that one liver lesion had high PSMA uptake. 18F-FDG PET/MRI revealed minimal FDG uptake in the liver lesion. Histopathological examination revealed that the liver lesion was moderately to poorly differentiated cholangiocarcinoma. Our studies, along with others, demonstrated that malignant liver tumors, such as ICC, hepatocellular carcinoma (HCC), and combined hepatocellular-cholangiocarcinoma (CHC), and benign lesions, such as benign liver hemangioma, focal nodular hyperplasia, focal inflammation and steatosis, vascular malformation, and fatty sparing, exhibited elevated PSMA uptake. Moreover, PSMA-PET was superior to FDG-PET in detecting ICC and HCC, indicating that PSMA-PET may be used as alternative staging and to identify patients for PSMA-targeted therapy.

Head-to-head comparison of prostate-specific membrane antigen PET and multiparametric MRI in the diagnosis of pretreatment patients with prostate cancer: a meta-analysis

OBJECTIVES

To compare prostate-specific membrane antigen (PSMA) PET with multiparametric MRI (mpMRI) in the diagnosis of pretreatment prostate cancer (PCa).

METHODS

Pubmed, Embase, Medline, Web of Science, and Cochrane Library were searched for eligible studies published before June 22, 2022. We assessed risk of bias and applicability by using QUADAS-2 tool. Data synthesis was performed with Stata 17.0 software, using the "midas" and "meqrlogit" packages.

RESULTS

We included 29 articles focusing on primary cancer detection, 18 articles about primary staging, and two articles containing them both. For PSMA PET versus mpMRI in primary PCa detection, sensitivities and specificities in the per-patient analysis were 0.90 and 0.84 (p<0.0001), and 0.66 and 0.60 (p <0.0001), and in the per-lesion analysis they were 0.79 and 0.78 (p <0.0001), and 0.84 and 0.82 (p <0.0001). For the per-patient analysis of PSMA PET versus mpMRI in primary staging, sensitivities and specificities in extracapsular extension detection were 0.59 and 0.66 (p =0.005), and 0.79 and 0.76 (p =0.0074), and in seminal vesicle infiltration (SVI) detection they were 0.51 and 0.60 (p =0.0008), and 0.93 and 0.96 (p =0.0092). For PSMA PET versus mpMRI in lymph node metastasis (LNM) detection, sensitivities and specificities in the per-patient analysis were 0.68 and 0.46 (p <0.0001), and 0.91 and 0.90 (p =0.81), and in the per-lesion analysis they were 0.67 and 0.36 (p <0.0001), and 0.99 and 0.99 (p =0.18).

CONCLUSION

PSMA PET has higher diagnostic value than mpMRI in the detection of primary PCa. Regarding the primary staging, mpMRI has potential advantages in SVI detection, while PSMA PET has relative advantages in LNM detection.

CLINICAL RELEVANCE STATEMENT

The integration of prostate-specific membrane antigen (PSMA) PET into the diagnostic pathway may be helpful for improving the accuracy of prostate cancer detection. However, further studies are needed to address the cost implications and evaluate its utility in specific patient populations or clinical scenarios. Moreover, we recommend the combination of PSMA PET and mpMRI for cancer staging.

KEY POINTS

• Prostate-specific membrane antigen PET has higher sensitivity and specificity for primary tumor detection in prostate cancer compared to multiparametric MRI. • Prostate-specific membrane antigen PET also has significantly better sensitivity and specificity for lymph node metastases of prostate cancer compared to multiparametric MRI. • Multiparametric MRI has better accuracy for extracapsular extension and seminal vesicle infiltration compared to ate-specific membrane antigen PET.

A comparison of [18F]AlF- and 68Ga-labeled dual targeting heterodimer FAPI-RGD in malignant tumor: preclinical evaluation and pilot clinical PET/CT imaging

Due to the heterogeneity of tumors, strategies to improve the effectiveness of dual-targeting tracers in tumor diagnostics have been intensively practiced. In this study, the radiolabeled [18F]AlF-NOTA-FAPI-RGD (denoted as [18F]AlF-LNC1007), a dual-targeting heterodimer tracer targeting both fibroblast activation protein (FAP) and integrin αvβ3 to enhance specific tumor uptake and retention, was synthesized and evaluated. The tracer was compared with [68Ga]Ga-LNC1007 in preclinical and clinical settings.

METHODS

The preparation of [18F]AlF- and 68Ga-labeled FAPI-RGD was carried out with an optimized protocol. The stability was tested in PBS and fetal bovine serum (FBS). Cellular uptake and in vivo distribution of the two products were compared and carried out on the U87MG cell line and its xenograft model. The safety and dosimetry of [18F]AlF-LNC1007 PET/CT scan were evaluated in six patients with malignant tumors.

RESULTS

Two radiolabeling protocols of [18F]AlF-/[68Ga]Ga-LNC1007 were developed and optimized to give a high yield of tracers with good stability. In vivo microPET images showed that the two tracers exhibited comparable pharmacokinetic characteristics, with high tumor uptake and prolonged tumor retention. In vivo distribution data showed that the target-to-non-target ratios of [18F]AlF-LNC1007 were similar to[68Ga]Ga-LNC1007. A total of six patients underwent [18F]AlF-LNC1007 PET/CT evaluation while two had head-to-head [18F]FDG PET/CT scans. The total body effective dose was 9.94E-03 mSv/MBq. The biodistribution curve showed optimal normal organ uptake with high tumor uptake and long retention of up to 3h p.i., and notably, the tumor-to-background ratio increased over time.

CONCLUSION

We successfully prepared an [18F]AlF-LNC1007 dual-targeting PET probe with comparable performances as [68Ga]Ga-LNC1007. With prolonged tumor retention and tumor specificity, it produced good imaging quality in preclinical and clinical translational studies, indicating that [18F]AlF-LNC1007 is a promising non-invasive tracer for detecting tumors expressing FAP and/or integrin avβ3, with the prospect of clinical implementation.

[ 18 F]-PSMA-1007 PET imaging optimization and inter-rater reliability - a comparison of three different reconstructions read by four radiologists

OBJECTIVES

To increase understanding of optimal imaging parameters [ 18 F]PSMA-1007 when imaging patients with prostate cancer and to determine interrater agreement using [ 18 F]PSMA-1007.

METHODS

In this observational study, four independent physicians read reconstruction sets using bedtimes of 1, 2 and 3 minutes of patients undergoing [ 18 F]PSMA-1007. positron emission topography. Clear and equivocal lesions and their locations were recorded. Image noise was rated on a four-point scale. Lesion counts were compared using inter-class correlation whereas noise ratings were compared using generalized estimating equations. Repeated cases were used to assess intra-rater agreement.

RESULTS

Sixty reconstruction sets of 16 consecutively examined participants were included. Participants had a mean age of 71.5 years, six of them were examined prior to any treatment, three had a history of radiotherapy and seven of prostatectomy. Median Gleason score of primary tumors was 7. Imaging was performed after a mean of 132 min using a mean 3.95 MBq/Kg body weight of [ 18 F] PSMA-1007. Neither the total number of lesions per location nor the proportion of equivocal lesions varied consistently between bedtimes. Inter-rater reliability scores varied depending on location from 0.40 to 1.0 and were similar for all bedtimes. Intra-rater reliability varied between 0.70 and 0.76 for the three different bedtimes. Noise ratings were significantly lower for 1 minute than 3 minutes per bed.

CONCLUSION

In the setting of [ 18 F]PSMA-1007 PET CT, 1, 2 and 3 minutes per bed produce similar results unlikely to affect clinical interpretation. Image noise ratings favor 2 and 3 minutes per bed.

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

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

ADVANCES IN KNOWLEDGE

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

Analytical performance validation of aPROMISE platform for prostate tumor burden, index and dominant tumor assessment with 18F-DCFPyL PET/CT. A pilot study

To validate the performance of automated Prostate Cancer Molecular Imaging Standardized Evaluation (aPROMISE) in quantifying total prostate disease burden with 18F-DCFPyL PET/CT and to evaluate the interobserver and histopathologic concordance in the establishment of dominant and index tumor. Patients with a recent diagnosis of intermediate/high-risk prostate cancer underwent 18F-DCFPyL-PET/CT for staging purpose. In positive-18F-DCFPyL-PET/CT scans, automated prostate tumor segmentation was performed using aPROMISE software and compared to an in-house semiautomatic-manual guided segmentation procedure. SUV and volume related variables were obtained with two softwares. A blinded evaluation of dominant tumor (DT) and index tumor (IT) location was assessed by both groups of observers. In histopathological analysis, Gleason, International Society of Urological Pathology (ISUP) group, DT and IT location were obtained. We compared all the obtained variables by both software packages using intraclass correlation coefficient (ICC) and Cohen's kappa coefficient (k) for the concordance analysis. Fifty-four patients with a positive 18F-DCFPyL PET/CT were evaluated. The ICC for the SUVmax, SUVpeak, SUVmean, tumor volume (TV) and total lesion activity (TLA) was: 1, 0.833, 0.615, 0.494 and 0.950, respectively (p < 0.001 in all cases). For DT and IT detection, a high agreement was observed between both softwares (k = 0.733; p < 0.001 and k = 0.812; p < 0.001, respectively) although the concordances with histopathology were moderate (p < 0001). The analytical validation of aPROMISE showed a good performance for the SUVmax, TLA, DT and IT definition in comparison to our in-house method, although the concordance was moderate with histopathology for DT and IT.

Is imaging accurate enough to detect index lesion in prostate cancer? Analysis of the performance of MRI and other imaging modalities

Prostate imaging techniques have progressed across the years allowing for a better detection and characterization of prostate cancer (PCa) lesions. These advancements have led to the possibility to also improve and tailor the treatments on the most aggressive lesion, defined as Index Lesion (IL), to reduce morbidity. The IL is, indeed, considered as the entity which encompass the most aggressive features in prostate cancer disease. Multiparametric magnetic resonance imaging (mpMRI) has emerged as the suggested tool to detect the disease and plan treatments, including those under investigation such as focal therapy (FT). Our review aimed to query the literature on the ability of mpMRI in IL detection and to explore the future perspectives in PCa IL diagnosis. A review of the literature was performed from January 2010 to July 2023. All studies investigating the performance of mpMRI and other main imaging techniques able to detect the IL were assessed and evaluated. mpMRI performs well in the detection of IL with a sensitivity which reaches 71% to 94% among the different studies. However, mpMRI seems to have limited sensitivity in the detection of small tumours (<0.5 mL) and low-grade histology lesions. To overcome these limitations other diagnostic imaging techniques have been proposed. Multiparametric Ultrasound has shown results comparable to mpMRI while detecting 4.3% fewer clinically significant PCa (P=0.042). Positron emission tomography-based modalities using PSMA seems to have higher sensitivity than mpMRI, being able to yield from 13.5% to 18.2% additional cancers. MRI has emerged as the recommended tool since most of the IL can be easily identified, and is the imaging of choice while selecting patients for FT. Other imaging modalities has been proposed to improve PCa lesions detection, but results need to be confirmed by ongoing randomized controlled trial.

A systematic review on the current status of PSMA-targeted imaging and radioligand therapy

Prostate specific membrane antigen (PSMA) has been the subject of several studies in recent decades as a promising molecular target for prostate cancer (PCa), in fact it is considered an excellent molecular target for both PCa imaging (both for staging and follow-up), by means of PET/CT and for radioligand therapy. Its interesting molecular features have enabled the development of a new diagnostic and therapeutic approach for PCa, called "theranostics." Considering the abundance of PSMA-based probes that have appeared so far in the literature, the present work focuses the attention on radiopharmaceuticals with increasing clinical application, highlighting advantages and disadvantages in terms of different metabolization and excretion processes, pharmacokinetic, binding affinity and variable internalization rate, tumor-to-background ratio, residence times and toxicity profile.

PSMA PET/MR is a New Imaging Option for Identifying Glioma Recurrence and Predicting Prognosis

BACKGROUND

Glioma is characterized by a high recurrence rate, while the results of the traditional imaging methods (including magnetic resonance imaging, MRI) to distinguish recurrence from treatment-related changes (TRCs) are poor. Prostate-specific membrane antigen (PSMA) (US10815200B2, Deutsches Krebsforschungszentrum, German Cancer Research Center) is a type II transmembrane glycoprotein overexpressed in glioma vascular endothelium, and it is a promising target for imaging and therapy.

OBJECTIVE

The study aimed to assess the performance of PSMA positron emission tomography/ magnetic resonance (PET/MR) for diagnosing recurrence and predicting prognosis in glioma patients.

MATERIALS AND METHODS

Patients suspected of glioma recurrence who underwent 18F-PSMA-1007 PET/MR were prospectively enrolled. Eight metabolic parameters and fifteen texture features of the lesion were extracted from PSMA PET/MR. The ability of PSMA PET/MR to diagnose glioma recurrence was investigated and compared with conventional MRI. The diagnostic agreement was assessed using Cohen κ scores and the predictive parameters of PSMA PET/MR were obtained. Kaplan-Meier method and Cox proportional hazard model were used to analyze recurrence- free survival (RFS) and overall survival (OS). Finally, the expression of PSMA was analyzed by immunohistochemistry (IHC).

RESULTS

Nineteen patients with a mean age of 48.11±15.72 were assessed. The maximum tumorto- parotid ratio (TPRmax) and texture features extracted from PET and T1-weighted contrast enhancement (T1-CE) MR showed differences between recurrence and TRCs (all p <0.05). PSMA PET/MR and conventional MRI exhibited comparable power in diagnosing recurrence with specificity and PPV of 100%. The interobserver concordance was fair between the two modalities (κ = 0.542, p = 0.072). The optimal cutoffs of metabolic parameters, including standardized uptake value (SUV, SUVmax, SUVmean, and SUVpeak) and TPRmax for predicting recurrence were 3.35, 1.73, 1.99, and 0.17 respectively, with the area under the curve (AUC) ranging from 0.767 to 0.817 (all p <0.05). In grade 4 glioblastoma (GBM) patients, SUVmax, SUVmean, SUVpeak, TBRmax, TBRmean, and TPRmax showed improved performance of AUC (0.833-0.867, p <0.05). Patients with SUVmax, SUVmean, or SUVpeak more than the cutoff value had significantly shorter RFS (all p <0.05). In addition, patients with SUVmean, SUVpeak, or TPRmax more than the cutoff value had significantly shorter OS (all p <0.05). PSMA expression of glioma vascular endothelium was observed in ten (10/11, 90.9%) patients with moderate-to-high levels in all GBM cases (n = 6/6, 100%).

CONCLUSION

This primitive study shows multiparameter PSMA PET/MR to be useful in identifying glioma (especially GBM) recurrence by providing excellent tumor background comparison, tumor heterogeneity, recurrence prediction and prognosis information, although it did not improve the diagnostic performance compared to conventional MRI. Further and larger studies are required to define its potential clinical application in this setting.

Bacteria-Based Living Probes: Preparation and the Applications in Bioimaging and Diagnosis

Bacteria can colonize a variety of in vivo biointerfaces, particularly the skin, nasal, and oral mucosa, the gastrointestinal tract, and the reproductive tract, but also target specific lesion sites, such as tumor and wound. By virtue of their prominent characteristics in motility, editability, and targeting ability, bacteria carrying imageable agents are widely developed as living probes for bioimaging and diagnosis of different diseases. This review first introduces the strategies used for preparing bacteria-based living probes, including biological engineering, chemical modification, intracellular loading, and optical manipulation. It then summarizes the recent progress of these living probes for fluorescence imaging, near-infrared imaging, ultrasonic imaging, photoacoustic imaging, magnetic resonance imaging, and positron emission tomography imaging. The biomedical applications of bacteria-based living probes are also reviewed particularly in the bioimaging and diagnosis of bacterial infections, cancers, and intestine-associated diseases. In addition, the advantages and challenges of bacteria-based living probes are discussed and future perspectives are also proposed. This review provides an updated overview of bacteria-based living probes, highlighting their great potential as a unique yet versatile platform for developing next-generation imageable agents for intelligent bioimaging, diagnosis, and even therapy.

Kinetic modeling and parametric imaging of 18 F-PSMA-11: An evaluation based on total-body dynamic positron emission tomography scans

BACKGROUND

The prostate-specific membrane antigen (PSMA) targeted positron-emitting tomography (PET) tracers are increasingly used in clinical practice, with novel tracers constantly being developed. Recently, 18 F-PSMA-11 has been gaining growing interest for several merits; however, direct in vivo visualization of its kinetic features in humans remains lacking.

PURPOSE

To visualize the kinetic features of 18 F-PSMA-11 in healthy subjects and patients with prostate cancer derived from the total-body dynamic PET scans.

METHODS

A total of 8 healthy volunteers (7 males; 1 female) and 3 patients with prostate cancer underwent total-body PET/CT imaging at 1 and 2 h post injection (p.i.) of 18 F-PSMA-11, of which 7 healthy subjects and 3 patients underwent total-body dynamic PET scans lasting 30 min. Reversible two-tissue compartments (2TC) and Patlak models were fitted based on the voxel-based time activity curves (TACs), with the parametric images generated subsequently. Additionally, semi-automated segmentation of multiple organs was performed in the dynamic images to measure the SUVmean at different time points and in the parametric images to estimate the mean value of the kinetic parameters of these organs.

RESULTS

18 F-PSMA-11 showed quick accumulation within prostate cancer, as early as 45 s after tracer injection. It was rapidly cleared from blood circulation and predominantly excreted through the urinary system. High and rapid radiotracer accumulation was observed in the liver, spleen, lacrimal glands, and salivary glands, whereas gradual accumulation was observed in the skeleton. Prostate cancer tissue is visualized in all parametric images, and best seen in DV and Patlak Ki images. Patlak Ki showed a good correlation with 2TC Ki values (r = 0.858, p < 0.05) but less noise than 2TC images. A scanning time point of 30-35 min p.i. was then suggested for satisfactory tumor to background ratio.

CONCLUSION

Prostate cancer tissue is visible in most parametric images, and is better shown by Patlak Ki and 2TC DV images. Patlak Ki is consistent with, and thus is preferred over, 2TC Ki images for substantially quicker calculation. Based on the dynamic imaging analysis, a shorter uptake time (30-35 min) might be preferred for a better balance of tumor to background ratio.

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.

Clinical Usefulness of Prostate-specific Membrane Antigen-ligand Positron Emission Tomography/Computed Tomography for the Detection of Prostate Cancer Biochemical Recurrence after Primary Radiation Therapy in Patients with Prostate-specific Antigen Below the Phoenix Threshold: Systematic Review and Meta-analysis

AIMS

After primary radiotherapy, biochemical recurrence is defined according to the Phoenix criteria as a prostate-specific antigen (PSA) value >2 ng/ml relative to the nadir. Several studies have shown that prostate-specific membrane antigen (PSMA)-ligand positron emission tomography/computed tomography (PET/CT) can help in detecting recurrence in patients with low PSA values. This study aimed to assess the detection rate and patterns of PSMA-ligand PET/CT uptake in patients with suspected biochemical recurrence after primary radiotherapy and with PSA levels below the Phoenix threshold.

MATERIALS AND METHODS

The meta-analysis was carried out in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Articles providing data on patients with suspected prostate cancer recurrence after primary radiotherapy with a PSA value below the Phoenix threshold and who underwent PSMA-ligand PET/CT were included. Quality assessment was carried out using the Quality Assessment of Diagnostic Accuracy Studies-2 tool (QUADAS-2).

RESULTS

In total, five studies were included, recruiting 909 patients (202 with PSA ≤2 ng/ml). The PSMA-ligand detection rate in the patients with ≤2 ng/ml ranged from 66 to 83%. The most frequent source of PSMA-ligand PET/CT uptake was local recurrence, followed by lymph node metastasis and bone metastasis. PSMA-ligand PET/CT uptake due to local-only recurrence was more likely in patients with PSA ≤2 ng/ml compared with PSA > 2 ng/ml: risk ratio 0.72 (95% confidence interval 0.58-0.89), P = 0.003. No significant differences were observed in the detection of PSMA-ligand uptake in other areas. Limitations include a lack of biopsy confirmation, cohort reports with small sample sizes and a potentially high risk of bias.

CONCLUSION

A significant detection of PSMA-ligand-avid disease was observed in patients with PSA levels below the Phoenix threshold. There was a higher likelihood of detecting local-only uptake when the PSA value was ≤2 ng/ml. The findings suggest that a critical review of the Phoenix criteria may be warranted in the era of PSMA-ligand PET/CT and highlight the need for further prospective trials.

The diagnostic accuracy of radiolabeled PSMA-ligand PET for tumour staging in newly diagnosed prostate cancer patients compared to histopathology: a systematic review and meta-analysis

PURPOSE

The current clinical recommendations posit the deployment of specific approved radiolabeled prostate-specific membrane antigen-ligand positron emission tomography (PSMA PET) for detecting metastatic prostate cancer during primary staging. Nevertheless, the precise efficacy of such ligands in localizing intraprostatic tumours (index tumour) and T-staging is not well established. Consequently, the objective of this inquiry is to ascertain the diagnostic accuracy of PSMA-PET in the tumour staging of newly diagnosed prostate cancer by means of a meta-analysis that integrates studies utilizing histological confirmation as the reference standard.

METHODS

In this study, we conducted a systematic literature search of the PubMed, Embase, Web of Science, and Cochrane Library databases using a predefined collection of search terms. These terms included 'PSMA PET', 'primary staging', and 'prostate cancer'. Subsequently, two independent reviewers evaluated all the studies based on predetermined inclusion criteria, extracted pertinent data, and assessed the quality of evidence. Any disparities were resolved by a third reviewer. A random effects Sidik-Jonkman model was applied to conduct a meta-analysis and estimate the diagnostic accuracy on a per-patient basis, along with 95% confidence intervals. Moreover, an appraisal regarding the likelihood of publication bias and the impact of small-study effects was performed utilizing both Egger's test and a graphical examination of the funnel plot.

RESULTS

The present analysis comprised a total of twenty-three scientific papers encompassing 969 patients and involved their analysis by both qualitative and quantitative approaches. The results of this study demonstrated that the estimated diagnostic accuracy of PSMA PET/CT and PSMA PET/MRI, for the detection of intraprostatic tumours, regardless of the type of PSMA-ligand, was 86% (95% CI: 76-96%) and 97% (95% CI: 94-100%), respectively. Furthermore, the diagnostic accuracy for the detection of extraprostatic extension (EPE) was 73% (95% CI: 64-82%) and 77% (95% CI: 69-85%), while the diagnostic accuracy for the detection of seminal vesicle involvement (SVI) was 87% (95% CI: 80-93) and 90% (95% CI: 82-99%), respectively.

CONCLUSION

The present investigation has demonstrated that PSMA PET/MRI surpasses currently recommended multiparametric magnetic resonance imaging (mpMRI) in terms of diagnostic accuracy as inferred from a notable data trajectory, whereas PSMA-PET/CT exhibited comparable diagnostic accuracy for intraprostatic tumour detection and T-staging compared to mpMRI. Nevertheless, the analysis has identified certain potential limitations, such as small-study effects and a potential for publication bias, which may impact the overall conclusions drawn from this study.

Can We Predict Skeletal Lesion on Bone Scan Based on Quantitative PSMA PET/CT Features?

OBJECTIVE

The increasing use of PSMA-PET/CT for restaging prostate cancer (PCa) leads to a patient shift from a non-metastatic situation based on conventional imaging (CI) to a metastatic situation. Since established therapeutic pathways have been designed according to CI, it is unclear how this should be translated to the PSMA-PET/CT results. This study aimed to investigate whether PSMA-PET/CT and clinical parameters could predict the visibility of PSMA-positive lesions on a bone scan (BS).

METHODS

In four different centers, all PCa patients with BS and PSMA-PET/CT within 6 months without any change in therapy or significant disease progression were retrospectively selected. Up to 10 non-confluent clear bone metastases were selected per PSMA-PET/CT and SUVmax, SUVmean, PSMAtot, PSMAvol, density, diameter on CT, and presence of cortical erosion were collected. Clinical variables (age, PSA, Gleason Score) were also considered. Two experienced double-board physicians decided whether a bone metastasis was visible on the BS, with a consensus readout for discordant findings. For predictive performance, a random forest was fit on all available predictors, and its accuracy was assessed using 10-fold cross-validation performed 10 times.

RESULTS

A total of 43 patients were identified with 222 bone lesions on PSMA-PET/CT. A total of 129 (58.1%) lesions were visible on the BS. In the univariate analysis, all PSMA-PET/CT parameters were significantly associated with the visibility on the BS (p < 0.001). The random forest reached a mean accuracy of 77.6% in a 10-fold cross-validation.

CONCLUSIONS

These preliminary results indicate that there might be a way to predict the BS results based on PSMA-PET/CT, potentially improving the comparability between both examinations and supporting decisions for therapy selection.

Protocol for SNOTOB study: radical prostatectomy without prostate biopsy following 18F-PSMA-1007 PET/CT based on a diagnostic model: a single-centre, single-arm, open-label study

INTRODUCTION

Nowadays, invasive prostate biopsy is the standard diagnostic test for patients with suspected prostate cancer (PCa). However, it has some shortcomings such as perioperative complications, economic and psychological burden on patients, and some patients may undergo repeated prostate biopsy. In this study protocol, our aim is to provide a non-invasive diagnostic strategy we call the 'prostate-specific membrane antigen (PSMA) combined model' for the diagnosis of PCa. If patients are diagnosed with PCa using PSMA combined model, we want to prove these patients can receive radical prostatectomy directly without prior prostate biopsies.

METHODS

The SNOTOB trial adopts a prospective, single-centre, single-arm, open-label study design. The PSMA combined model consists of a diagnostic model based on what we previously reported and 18F-PSMA-1007 positron emission tomography/CT (18F-PSMA-1007 PET/CT) examinations in series. First, patients use the diagnostic model (online address: https://ustcprostatecancerprediction.shinyapps.io/dynnomapp/) to calculate the risk probability of clinically significant PCa (csPCa). When the risk probability of csPCa is equal or greater than 0.60, 18F-PSMA-1007 PET/CT will be applied for further diagnosis. If patients are still considered as csPCa after 18F-PSMA-1007 PET/CT examinations, we define this condition as positive results of PSMA combined model. Subsequently, we will recommend these patients to accept radical prostatectomy without prostate biopsy directly. Finally, the diagnostic performance of PSMA combined model will be verified with the pathological results. Totally, 57 patients need to be enrolled in this clinical trial.

ETHICS AND DISSEMINATION

This study was approved by the ethics committee of The First Affiliated Hospital of USTC (No. 2022KY-142). The results of this study will be published in peer-reviewed journals and reported at academic conferences.

TRIAL REGISTRATION NUMBER

NCT05587192.

Deep learning based automated delineation of the intraprostatic gross tumour volume in PSMA-PET for patients with primary prostate cancer

PURPOSE

With the increased use of focal radiation dose escalation for primary prostate cancer (PCa), accurate delineation of gross tumor volume (GTV) in prostate-specific membrane antigen PET (PSMA-PET) becomes crucial. Manual approaches are time-consuming and observer dependent. The purpose of this study was to create a deep learning model for the accurate delineation of the intraprostatic GTV in PSMA-PET.

METHODS

A 3D U-Net was trained on 128 different 18F-PSMA-1007 PET images from three different institutions. Testing was done on 52 patients including one independent internal cohort (Freiburg: n = 19) and three independent external cohorts (Dresden: n = 14 18F-PSMA-1007, Boston: Massachusetts General Hospital (MGH): n = 9 18F-DCFPyL-PSMA and Dana-Farber Cancer Institute (DFCI): n = 10 68Ga-PSMA-11). Expert contours were generated in consensus using a validated technique. CNN predictions were compared to expert contours using Dice similarity coefficient (DSC). Co-registered whole-mount histology was used for the internal testing cohort to assess sensitivity/specificity.

RESULTS

Median DSCs were Freiburg: 0.82 (IQR: 0.73-0.88), Dresden: 0.71 (IQR: 0.53-0.75), MGH: 0.80 (IQR: 0.64-0.83) and DFCI: 0.80 (IQR: 0.67-0.84), respectively. Median sensitivity for CNN and expert contours were 0.88 (IQR: 0.68-0.97) and 0.85 (IQR: 0.75-0.88) (p = 0.40), respectively. GTV volumes did not differ significantly (p > 0.1 for all comparisons). Median specificity of 0.83 (IQR: 0.57-0.97) and 0.88 (IQR: 0.69-0.98) were observed for CNN and expert contours (p = 0.014), respectively. CNN prediction took 3.81 seconds on average per patient.

CONCLUSION

The CNN was trained and tested on internal and external datasets as well as histopathology reference, achieving a fast GTV segmentation for three PSMA-PET tracers with high diagnostic accuracy comparable to manual experts.

Head-to-head comparisons of 68Ga-PSMA-11 and 18F-FDG PET/CT in evaluating patients with upper tract urothelial carcinoma: a prospective pilot study

PURPOSE

To prospectively compare the uptake of 68Ga-prostate specific membrane antigen (68Ga-PSMA)-11 and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in upper tract urothelial carcinoma (UTUC) and investigate the correlation between radiological parameters and pathological features of UTUC.

METHODS

Clinicopathologic and imaging data were collected from 10 UTUC patients who underwent preoperative 68Ga-PSMA-11 and 18F-FDG PET/CT scans. The diagnostic capabilities of both imaging techniques were analyzed and compared in UTUC. Angiogenesis in the malignancies was assessed using Chalkley counting and the expression of folate hydrolase 1 (FOLH1) and glucose transporter 1 (GLUT1) in UTUC were evaluated in the surgical specimens. Double immunofluorescence staining of PSMA and CD34 was used to examine tumor neovascularization. Tracer uptake and expression were compared and explored. Additionally, 10 patients with clear cell renal cell carcinoma (ccRCC) were included for prospective, comparative research.

RESULTS

Ten UTUC patients with 12 malignant lesions and another 10 ccRCC patients were included. 18F-FDG PET/CT demonstrated a more effective detection of UTUC foci compared to 68Ga-PSMA-11 PET/CT (the SUVmax of 18.48 ± 6.73 vs. 4.38 ± 1.45, P < 0.01). Immunohistochemical analysis revealed a statistically significant difference in the expression of PSMA and GLUT1 in UTUC (P = 0.048), with higher pathological grades showing more intense GLUT1 staining than PSMA (75% vs. 12.5%). The Chalkley counting of angiogenesis in ccRCC was significantly higher than that in UTUC (229.34 vs. 71.67), which was proportional to 68Ga-PSMA-11 PET/CT SUVmax (both P < 0.05).

CONCLUSION

18F-FDG PET/CT holds better clinical potential for evaluating UTUC and detecting lymph node metastasis compared to 68Ga-PSMA-11 PET/CT, likely due to the relatively scant expression of FOLH1 in tumor neovascular endothelium while the abundant expression of GLUT1 in malignancy. Furthermore, the lower neovascular density in UTUC should not be overlooked.