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

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.

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.

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.

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.

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.

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.

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.

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.

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.

Recent Pre-Clinical Advancements in Nuclear Medicine: Pioneering the Path to a Limitless Future

The theranostic approach in oncology holds significant importance in personalized medicine and stands as an exciting field of molecular medicine. Significant achievements have been made in this field in recent decades, particularly in treating neuroendocrine tumors using 177-Lu-radiolabeled somatostatin analogs and, more recently, in addressing prostate cancer through prostate-specific-membrane-antigen targeted radionuclide therapy. The promising clinical results obtained in these indications paved the way for the further development of this approach. With the continuous discovery of new molecular players in tumorigenesis, the development of novel radiopharmaceuticals, and the potential combination of theranostics agents with immunotherapy, nuclear medicine is poised for significant advancements. The strategy of theranostics in oncology can be categorized into (1) repurposing nuclear medicine agents for other indications, (2) improving existing radiopharmaceuticals, and (3) developing new theranostics agents for tumor-specific antigens. In this review, we provide an overview of theranostic development and shed light on its potential integration into combined treatment strategies.

PET imaging of new target CDK19 in prostate cancer

PURPOSE

Prostate-specific membrane antigen (PSMA)-positron emission tomography (PET) is a superior method to predict patients' risk of cancer progression and response to specific therapies. However, its performance is limited for neuroendocrine prostate cancer (NEPC) and PSMA-low prostate cancer cells, resulting in diagnostic blind spots. Hence, identifying novel specific targets is our aim for diagnosing those prostate cancers with low PSMA expression.

METHODS

The Cancer Genome Atlas (TCGA) database and our cohorts from men with biopsy-proven high-risk metastatic prostate cancer were used to identify CDK19 and PSMA expression. PDX lines neP-09 and P-16 primary cells were used for cellular uptake and imaging mass cytometry in vitro. To evaluate in vivo CDK19-specific uptake of gallium(Ga)-68-IRM-015-DOTA, xenograft mice models and blocking assays were used. PET/CT imaging data were obtained to estimate the absorbed dose in organs.

RESULTS

Our study group had reported the overexpression of a novel tissue-specific gene CDK19 in high-risk metastatic prostate cancer and CDK19 expression correlated with metastatic status and tumor staging, independently with PSMA and PSA levels. Following up on this new candidate for use in diagnostics, small molecules targeting CDK19 labeled with Ga-68 (68Ga-IRM-015-DOTA) were used for PET in this study. We found that the 68Ga-IRM-015-DOTA was specificity for prostate cancer cells, but the other cancer cells also took up little 68Ga-IRM-015-DOTA. Importantly, mouse imaging data showed that the NEPC and CRPC xenografts exhibited similar signal strength with 68Ga-IRM-015-DOTA, but 68Ga-PSMA-11 only stained the CRPC xenografts. Furthermore, target specificity was elucidated by a blocking experiment on a CDK19-bearing tumor xenograft. These data concluded that 68Ga-CDK19 PET/CT was an effective technology to detect lesions with or without PSMA in vitro, in vivo, and in the PDX model.

CONCLUSION

Thus, we have generated a novel PET small molecule with predictive value for prostate cancer. The findings indicate that 68Ga-CDK19 may merit further evaluation as a predictive biomarker for PET scans in prospective cohorts and may facilitate the identification of molecular types of prostate cancer independent of PSMA.

Meta-analysis of 18 F-PSMA-1007 PET/CT, 18 F-FDG PET/CT, and 68Ga-PSMA PET/CT in diagnostic efficacy of prostate Cancer

OBJECTIVE

To compare 18 F-PSMA-1007 PET/CT, 18 F-FDG PET/CT and 68Ga-PSMA PET/CT in the diagnostic value of prostate cancer.

METHOD

The Chinese and foreign databases, such as Pubmed, Cochrane Library, Embase, CNKI, VIP, Wanfang, etc., were systematically searched within the period from the establishment of the database to June 1, 2022. Clinical studies related to the diagnosis of prostate cancer by methods such as 18 F-PSMA-1007 PET/CT, 18 F-FDG PET/CTCT, 68Ga-PSMA PET/CT, were researched. Two (2) investigators independently screened literatures, extracted data, and assessed the risk of bias when these data were included in the studies with the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2). Review Manager5.4, Stata 14.0, and Meta-disc 1.4 software were used for meta-analysis to compare the efficacy of different methods in the diagnose of prostate cancer.

RESULTS

Twenty-seven (27) studies, including 2891 subjects were included in our study. Meta-analysis results showed that the pooled sensitivities of 18 F-PSMA-1007 PET/CT, 18 F-FDG PET/CT, and 68Ga-PSMA PET/CT were 0.912 (95%CI: 0.883-0.936), 0.748 (95%CI: 0.698-0.795), and 0.916 (95%CI: 0.896-0.934), respectively; the pooled specification were 0.878 (0.844-0.907), 0.639 (95%CI: 0.589-0.687), and 0.734 (95%CI: 0.685-0.779), respectively; the positive likelihood ratios were 6.335 (95%CI: 4.288-9.357), 2.282 (95%CI: 1.497-3.477), and 3.593 (95%CI: 2.986-4.323), respectively; the negative likelihood ratios were 0.878 (95%CI: 0.844-0.907), 0.374 (95%CI: 0.280-0.499), and 0.110 (95%CI: 0.083-0.144), respectively; the diagnostic odds ratios were 65.125 (95%CI: 34.059-124.53), 7.094 (95%CI: 4.091-12.301), and 29.722 (95%CI: 20.141-43.863), respectively; the positive posterior probability was 64%, 38%, and 62%, respectively; the area under the SPOC curve was 0.95 (95%CI: 0.93-0.97), 0.81 (95%CI: 0.78-0.84), and 0.96 (95%CI: 0.92-0.98), respectively. The funnel plots indicated that there was no significant publication bias in the included literatures.

CONCLUSION

The current evidences showed that 18 F-PSMA-1007 PET/CT and 68Ga-PSMA PET/CT had higher diagnostic efficacy of prostate cancer compared with 18 F-FDG PET/CT, among which 68Ga-PSMA PET/CT was slightly higher in the sensitivity of the diagnosis of prostate cancer, while 18 F-PSMA-1007 PET/CT may have higher efficacy in specificity and confirmed positive rate. Due to the limitations of the quality of the included samples and literatures, the above conclusions should be further validated by expanding the sample size and improving the quality.

Comparison of the Effects of DOTA and NOTA Chelators on 64Cu-Cudotadipep and 64Cu-Cunotadipep for Prostate Cancer

BACKGROUND

This study compared the effects of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) as 64Cu-chelating agents in newly developed prostate-specific membrane antigen (PSMA) target compounds, 64Cu-cudotadipep and 64Cu-cunotadipep, on pharmacokinetics.

METHODS

The in vitro stability of the chelators was evaluated using human and mouse serum. In vitro PSMA-binding affinity and cell uptake were compared using human 22Rv1 cells. To evaluate specific PSMA-expressing tumor-targeting efficiency, micro-positron emission tomography (mcroPET)/computed tomography (CT) and biodistribution analysis were performed using PSMA+ PC3-PIP and PSMA- PC3-flu tumor xenografts.

RESULTS

The serum stability of DOTA- or NOTA-conjugated 64Cu-cudotadipep and 64Cu-cunotadipep was >97%. The Ki value of the NOTA derivative, cunotadipep, in the in vitro affinity binding analysis was higher (2.17 ± 0.25 nM) than that of the DOTA derivative, cudotadipep (6.75 ± 0.42 nM). The cunotadipep exhibited a higher cellular uptake (6.02 ± 0.05%/1 × 106 cells) compared with the cudotadipep (2.93 ± 0.06%/1 × 106 cells). In the biodistribution analysis and microPET/CT imaging, the 64Cu-labeled NOTA derivative, 64Cu-cunotadipep, demonstrated a greater tumor uptake and lower liver uptake than the DOTA derivative.

CONCLUSIONS

This study indicates that the PSMA-targeted 64Cu-cunotadipep can be applied in clinical practice owing to its high diagnostic power for prostate cancer.

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 .

Impact of non-regional lymph node metastases accurately revealed on 18F-PSMA-1007 PET/CT in the clinical management of metastatic hormone-sensitive prostate cancer

BACKGROUND

Non-regional lymph node (NRLN) metastases has shown increasing importance in the prognosis evaluation and clinical management of primary metastatic hormone-sensitive prostate cancer (mHSPC). Hence, this study aimed to investigate the concordance rates between ¹⁸F-PSMA-1007 PET/CT and conventional imaging (CI) in revealing NRLN metastases, and explore the impact of NRLN metastases on the management of primary mHSPC.

METHODS

The medical records of 224 patients with primary mHSPC were retrospectively reviewed, including 101 patients (45.1%) only received CI for TNM classification, 24 patients (10.7%) only received ¹⁸F-PSMA-1007 PET/CT, and 99 patients (44.2%) received both ¹⁸F-PSMA-1007 PET/CT and CI. Among patients who received ¹⁸F-PSMA-1007 PET/CT and CI before initial treatment, the concordance rates between ¹⁸F-PSMA-1007 PET/CT and CI were analyzed. The high-volume disease was defined as the presence of visceral metastases and/or ≥ 4 bone metastases (≥ 1 beyond the vertebral bodies or the pelvis) based on the findings of ¹⁸F-PSMA-1007 PET/CT and/or CI. The primary endpoint was progression-free survival (PFS), and Cox regression analyses were performed to explore independent predictors of PFS.

RESULTS

A total of 99 patients (44.2%) received both ¹⁸F-PSMA-1007 PET/CT and CI, the concordance rate in revealing NRLN metastases between ¹⁸F-PSMA-1007 PET/CT and CI was only 61.62%, and Cohen's kappa coefficient was as low as 0.092. Moreover, ¹⁸F-PSMA-1007 PET/CT detected an additional 37 of 94 (39.4%) patients with positive NRLNs who were negative on CI. Cox regression revealed that androgen deprivation therapy (ADT), N1, high-volume, NRLN and visceral metastases were associated with worse PFS (all P < 0.05) in 224 patients. Furthermore, in patients with low-volume disease, the median PFS of patients with NRLN metastases was significantly shorter than that of patients without NRLN metastases (19.5 vs. 27.5 months, P = 0.01), while the difference between patients with low-volume plus NRLN metastases and high-volume disease was not significant (19.5 vs. 16.9 months, P = 0.55). Moreover, early docetaxel chemotherapy significantly prolonged the PFS of these patients compared with ADT alone (20.7 vs. 12.3 months, P = 0.008).

CONCLUSION

NRLN metastases could be accurately revealed by ¹⁸F-PSMA-1007 PET/CT, which should be considered a high-volume feature, especially concomitant with bone metastases. Furthermore, patients with low-volume plus NRLN metastases may be suitable for more intensive treatment, such as early docetaxel chemotherapy.

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.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

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.

The prognostic value of 18F-PSMA-1007 PET/CT in predicting pathological upgrading of newly diagnosed prostate cancer from systematic biopsy to radical prostatectomy

Objective

This study aimed to evaluate predictors for upgrading of newly diagnosed prostate cancer from systematic biopsy (SB) to radical prostatectomy (RP) using fluorine-18 prostate-specific membrane antigen 1007 (¹⁸F-PSMA-1007) positron emission tomography/computed tomography (PET/CT) and association with clinical parameters.

Materials and methods

We retrospectively collected data from biopsy-confirmed prostate cancer (PCa) patients who underwent ¹⁸F-PSMA-1007 PET/CT prior to RP from July 2019 and October 2022. Imaging characteristics derived from ¹⁸F-PSMA-1007 PET/CT and clinical parameters were compared in patients of pathological upgrading and concordance subgroups. Univariable and multivariable logistic regressions were performed to analyze factors predicting histopathological upgrading from SB to RP specimens. Discrimination ability of independent predictors was further evaluated by receiver operating characteristic (ROC) analysis with corresponding area under the curve (AUC).

Results

Pathological upgrading occurred in 26.97% (41/152) PCa patients, and 23.03% (35/152) of all patients experienced pathological downgrading. Concordance rate reached 50% (76/152). International Society of Urological Pathology grade group (ISUP GG) 1(77.78%) and ISUP GG 2 (65.22%) biopsies were related with the highest rate of upgrading. Multivariable logistic regression analyses showed that prostate volume (OR= 0.933; 95% CI, 0.887-0.982; p = 0.008), ISUP GG 1 vs. 4 (OR= 13.856; 95% CI: 2.467-77.831; p = 0.003), and total uptake of PSMA-avid lesions (PSMA-TL) (OR = 1.003; 95% CI, 1.000-1.006; p = 0.029) were found to be independent risk factors of pathological upgrading after RP. The AUCs and corresponding sensitivity and specificity of the independent predictors of synthesis for upgrading were 0.839, 78.00%, and 83.30% respectively, which showed good discrimination capacity.

Conclusion

¹⁸F-PSMA-1007 PET/CT may help to predict pathological upgrading between biopsy and RP specimens, particularly for ISUP GG 1 and ISUP GG 2 patients with higher PSMA-TL and smaller prostate volume.

Increased Petrous Bone Uptake on 18 F-PSMA-1007 PET/CT Due to Otospongiosis

ABSTRACT

We report the case of a 74-year-old man who had undergone radical prostatectomy for prostatic cancer 6 months earlier. Elevated prostate-specific antigen during follow-up prompted 18 F-prostate-specific membrane antigen (PSMA) ligand PET/CT ( 18 F-PSMA-1007 PET/CT) to search for new manifestations of prostate cancer, revealing an increased focal uptake (SUV max , 5.9) in the left cochlear/pericochlear temporal bone and equivocal PSMA-RADS-3a external iliac nodes. Comparison with cone-beam CT and MRI showed that the focal temporal bone uptake corresponded to the typical morphological features of active otospongiosis (otosclerosis) in the context of a previously known long-standing otospongiosis.

ACR Appropriateness Criteria® Pretreatment Detection, Surveillance, and Staging of Prostate Cancer: 2022 Update

Prostate cancer is second leading cause of death from malignancy after lung cancer in American men. The primary goal during pretreatment evaluation of prostate cancer is disease detection, localization, establishing disease extent (both local and distant), and evaluating aggressiveness, which are the driving factors of patient outcomes such as recurrence and survival. Prostate cancer is typically diagnosed after the recognizing elevated serum prostate-specific antigen level or abnormal digital rectal examination. Tissue diagnosis is obtained by transrectal ultrasound-guided biopsy or MRI-targeted biopsy, commonly with multiparametric MRI without or with intravenous contrast, which has recently been established as standard of care for detecting, localizing, and assessing local extent of prostate cancer. Although bone scintigraphy and CT are still typically used to detect bone and nodal metastases in patients with intermediate- or high-risk prostate cancer, novel advanced imaging modalities including prostatespecific membrane antigen PET/CT and whole-body MRI are being more frequently utilized for this purpose with improved detection rates. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

A Systematic Review of the Variability in Performing and Reporting Intraprostatic Prostate-specific Membrane Antigen Positron Emission Tomography in Primary Staging Studies

Context

Prostate cancer (PCa) remains one of the leading causes of cancer-related deaths in men worldwide. Men at risk are typically offered multiparametric magnetic resonance imaging and, if suspicious, a targeted biopsy. However, false-negative rates of magnetic resonance imaging are consistently 18%; therefore, there is growing interest in improving the diagnostic performance of imaging through novel technologies. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is being utilised for PCa staging and, more recently, for intraprostatic tumour localisation. However, significant variability has been observed in how PSMA PET is performed and reported.

Objective

In this review, we aim to evaluate how pervasive this variability is in trials investigating the performance of PSMA PET in primary PCa workup.

Evidence acquisition

Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, we performed an optimal search in five different databases. After removing duplicates, 65 studies were included in our review.

Evidence synthesis

Studies dated back as early as 2016, with numerous different source countries. There was variation in the reference standard for PSMA PET, with some using biopsy specimens or surgical specimens, and in some cases, a combination of the two. Similar inconsistencies were noted when studies selected histological definitions of clinically significant PCa, while some omitted their definition altogether. The most significant variations in performing PSMA PET were the radiotracer type, dose, acquisition time after injection, and the PET camera being utilised. Substantial variation in the reporting of PSMA PET was noted, with no consistency in defining what constitutes a positive intraprostatic lesion. Across 65 studies, four different definitions were used.

Conclusions

This systematic review has highlighted considerable variation in obtaining and performing a PSMA PET study in the context of primary PCa diagnosis. Given the discrepancy in how PSMA PET was performed and reported, it questions the homogony of studies from centre to centre. Standardisation of PSMA PET is required for this to become a consistently useful and reproducible modality in the diagnosis of PCa.

Patient summary

Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is being utilised for staging and localisation of prostate cancer (PCa); however, there is significant variability in performing and reporting PSMA PET. Standardisation of PSMA PET is required for results to be consistently useful and reproducible for the diagnosis of PCa.

Status of 18F-PSMA-1007-PET/CT compared with multiparametric MRI in preoperative evaluation of prostate cancer

PURPOSE

Treatment of primary prostate cancer extremely depends on preoperative stage. The role of ¹⁸F-1007-PSMA-PET/CT in preoperative staging has not been well defined. Our aim was to compare the diagnostic performance of ¹⁸F-1007-PEMA-PET/CT, mpMRI, and mpMRI + PEMA-PET/CT in local progression and lymph node invasion of prostate cancer using histopathology as the gold standard.

MATERIALS AND METHODS

In this retrospective study, all patients with prostate cancer who underwent mpMRI and ¹⁸F-PSMA-1007-PET/CT before operation were included. The role of preoperative imaging was evaluated by predicting the sensitivity and specificity of EPE (extraprostatic extension), SVI (seminal vesicle invasion), and lymph node invasion results.

RESULTS

Ultimately, 130 patients were included in this study. In the preoperative judgment of EPE and SVI, mpMRI + PSMA-PET/CT had higher sensitivity and specificity. When predicting lymph node metastasis, PSMA-PET/CT was the best choice. The accuracy of mpMRI + PSMA-PET/CT and PSMA-PET/CT in the T and N stages, respectively, was affected by the least factors.

CONCLUSIONS

Based on the combined results of mpMRI and ¹⁸F-1007-PSMA-PET/CT, the accuracy of the preoperative judgment of prostatic capsule invasion can be improved, which may be conducive to developing intra-fascial technology while ensuring no tumor-touch isolation. PSMA-PET/CT has the advantages over mpMRI alone in terms of lymph node positivity. Compared with PSMA-PET/CT alone, the combined results can improve the sensitivity, but reduce specificity. Therefore, it is recommended to focus on PSMA-PET/CT to decide whether lymph node dissection should be performed.

Head-to-head comparisons of [68Ga]Ga-PSMA-11 PET/CT, multiparametric MRI, and prostate-specific antigen for the evaluation of therapeutic responses to neoadjuvant chemohormonal therapy in high-risk non-metastatic prostate cancer patients: a prospective study

PURPOSE

The optimal tool to evaluate the tumour therapeutic responses to neoadjuvant chemohormonal therapy (NCHT) in patients with high-risk non-metastatic prostate cancer (PCa) remains uncertain. We compared the role of [⁶⁸Ga]-labeled prostate-specific membrane antigen (PSMA)-11 positron emission tomography/computerized tomography ([⁶⁸Ga]Ga-PSMA-11 PET/CT), multiparametric MRI (mpMRI), and prostate-specific antigen (PSA) and assessed the practical value of the recent European Association of Urology and European Association of Nuclear Medicine (EAU/EANM) recommended criteria of PSMA PET/CT to evaluate the therapeutic responses to NCHT in patients with high-risk non-metastatic PCa.

METHODS

This prospective study included 72 high-risk non-metastatic PCa patients receiving NCHT followed by radical prostatectomy from June 2021 to March 2022. PSA testing, [⁶⁸Ga]Ga-PSMA-11 PET/CT, and mpMRI scanning were conducted in all patients before and after NCHT. Therapeutic responses to NCHT were evaluated with PSA, RECIST 1.1, PERCIST 1.0, and EAU/EANM recommended criteria. Postoperative pathological results were considered the reference standard. A favourable pathological response was defined as pathologic complete remission (pCR) or minimal residual disease (MRD). Diagnostic accuracy was assessed by sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), positive predictive value (PPV), negative predictive value (NPV), and Cohen's kappa index. Logistic regression analysis was used to determine the independent predictive value of [⁶⁸Ga]Ga-PSMA-11 PET/CT-derived parameters.

RESULTS

All cases experienced a marked decrease in PSA levels after NCHT. Twenty-four (33.33%) cases experienced a favourable pathological response, including five (6.94%) cases of pCR and 19 (26.39%) cases of MRD. According to the results of [⁶⁸Ga]Ga-PSMA-11 PET/CT, EAU/EANM recommended criteria indicated that 20 (27.78%) cases had a CR, whereas PERCIST 1.0 criteria indicated that 23 (31.94%) cases had a CR. There was a strong association between EAU/EANM recommended criteria and PERCIST 1.0 criteria (Pearson's R=0.857). The sensitivity (75.00%, 79.17% vs. 58.33%, 58.33%), specificity (95.83%, 91.67% vs. 83.33%, 68.75%), PLR (18.00, 9.50 vs. 3.50, 1.87), NLR (0.26, 0.23 vs. 0.50, 0.61), PPV (90.0%, 82.6% vs. 63.6%, 48.3%), and NPV (88.5%, 89.8% vs. 80.0%, 76.7%) of [⁶⁸Ga]Ga-PSMA-11 PET/CT (including EAU/EANM recommended criteria and PERCIST 1.0 criteria) to predict favourable pathological responses were all superior to those of mpMRI and nadir PSA. The kappa index to predict a favourable pathological response was 0.257 for PSA, 0.426 for RECIST 1.1, 0.716 for PERCIST 1.0, and 0.739 for EAU/EANM recommended criteria. Multivariate logistic analysis revealed that the post-NCHT maximum standardized uptake value (SUVmax) before radical prostatectomy was an independent predictor of a favourable pathological response to NCHT.

CONCLUSIONS

[⁶⁸Ga]Ga-PSMA-11 PET/CT had a better concordance with a favourable pathological response to NCHT compared with nadir PSA and mpMRI. EAU/EANM recommended criteria and PERCIST 1.0 criteria performed equally to identify pathological responders when [⁶⁸Ga]Ga-PSMA-11 PET/CT was used as a therapeutic response assessment tool.

(18F)-PSMA-1007PET/CT in patients with biochemical recurrence after radical prostatectomy: Diagnostic performance and impact on treatment management

Objective

To evaluate the diagnostic performance of (18F)-PSMA-1007 PET/CT in prostate cancer patients with biochemical recurrence (BCR) after radical prostatectomy and the effect of (18F)-PSMA-1007 PET/CT on treatment strategy.

Methods

A total of 114 patients with BCR after radical prostatectomy who performed (18F)-PSMA-1007 PET/CT were retrospectively analyzed. The Gleason scores (GS), maximum standardized uptake values (SUVmax) and the diagnostic performance were compared according to different prostate-specific antigen (PSA) groups. To evaluate the impact of (18F)-PSMA-1007 PET/CT on treatment management, we also collected subjects' therapy before and after PET/CT. The PSA value was monitored to evaluate the biochemical response.

Results

(18F)-PSMA-1007PET/CT was positive in 92/114 patients (80.7%). The detection rates were 20/34 (58.8%), 13/17 (76.5%), 15/17 (88.2%) and 44/46 (95.7%) for PSA levels of 0.2-<0.5, 0.5-<1, 1-<2, ≥2 ng/ml. The positive lesions on PET/CT revealed local recurrence in 24/114 (21.1%) patients, lymph nodes metastases in 54/114 (47.4%) and metastatic sites in bone, lung, and others in 75/114 (65.8%). A significant positive correlation was observed between the GS/ SUVmax and PSA level (r1 = 0.375, r2 = 0.336, P<0.001). As a result of the (18F)-PSMA-1007 PET/CT, therapeutic decision-making changed in 60/114 (52.6%) patients. With a follow-up of 11.0 ± 6.4 months, 81/114 PSA were collected after treatment guided by (18F)-PSMA-1007 PET/CT, and in 42/81 (51.9%) of patients, serum PSA levels decreased of more than 60%.

Conclusion

(18F)-PSMA-1007 PET/CT has a high lesion detection rate for recurrent prostate cancer (PCa) and could have significant implications in decision-making treatment plan for the majority of PCa patients.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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