PSMA PET in Prostate Cancer

Correlations Between MR Apparent Diffusion Coefficients and PET Standard Uptake Values in Simultaneous MR-PET Imaging of Prostate Cancer

This study evaluated the hypothesis that 68Ga-PSMA-11 PET SUV, obtained via an advanced DL approach, correlates better with MR ADC maps than values from conventional PET-MR. Additionally, we aimed to identify the optimal SUV threshold for maximum correlation with ADC values. A cohort of 32 prostate cancer patients underwent CT and corresponding PET-MR imaging. The dataset underwent K-fold cross-validation, dividing it into four folds. In each fold, 24 patients were used for training, and 8 for validation to create DL models. ADC maps from 27 out of 32 patients were successfully aligned with T2 images for detailed analysis, revealing an inverse correlation (ρ = -0.20 to -0.51) between ADC and SUV values in prostate cancer zones. Statistically significant differences in mean SUV values were observed between PETMRI and PETDL. DL-based SUV values show a stronger correlation with ADC than conventional PET-MR values in our investigation.

Time-efficient HPLC Validation Methodology for the Qualitative Analysis of 68Ga PSMA-11 in Routine Clinical Usage under Isocratic Method

Background

Prostate-specific membrane antigen (PSMA) has shown to be a promising agent for prostate cancer imaging under PET-CT. With the automation in radiolabeling with 68Ga, using iTG 68Ge/68Ga generator, it has helped introduce various new diagnostic agents and achieve good manufacturing practices (GMP) simultaneously. However, before any radiopharmaceutical is put into clinical usage, it should always be checked for its radiochemical purity and other quality parameters before injecting in the patient. Chromatography techniques such as Gas Chromatography (GC), High-Performance Liquid Chromatography (HPLC), and Thin-Layer Chromatography (TLC) are the most frequently utilized separation technique for purity analysis. A rapid quality control HPLC based methodology was required for radiopharmaceuticals.

Aim & Objective

In our current setting, we conducted quality control analysis and standardized and validated HPLC method for the routine quality check of 68Ga-PSMA-11.

Materials and Methods

The QC of 68Ga PSMA-11 was performed under ITLC and HPLC.

Results

Linearity, accuracy, precision and specificity were assessed and quantified in accordance with International conference on harmonisation of technical requirements for registration of pharmaceuticals for human use (Q2 (R1) ICH) guidelines, which can be implemented in resource-limited settings to check the quality.

Conclusion

The current HPLC based methodology is rapid, with a retention time of 2.24 min, rendering it a favorable analytical standard operating procedure for QC analysis of 68Ga-PSMA-11.

Impact of Region-of-Interest Delineation on Stability and Reproducibility of Liver SNR Measurements in 68 Ga-PSMA PET/CT

Objective  This study aims to assess the impact of various regions of interest (ROIs) and volumes of interest (VOIs) delineations on the reproducibility of liver signal-to-noise-ratio (SNRliver) measurements, as well as to find the most reproducible way to estimate it in gallium-68 positron emission tomography ( ⁶⁸ Ga-PET) imaging. We also investigated the SNRliver-weight relationship for these ROIs and VOIs delineations. Methods  A cohort of 40 patients (40 males; mean weight: 76.5 kg [58-115 kg]) with prostate cancer were included. ⁶⁸ Ga-PET/CT imaging (mean injected activity: 91.4 MBq [51.2 MBq to 134.1 MBq] was performed on a 5-ring bismuth germanium oxide-based Discovery IQ PET/CT using ordered subset expectation maximization image reconstruction algorithm. Afterward, circular ROIs and spherical VOIs with two different diameters of 30 and 40 mm were drawn on the right lobe of the livers. The performance of the various defined regions was evaluated by the average standardized uptake value (SUV _mean ), standard deviation (SD) of the SUV (SUV _SD ), SNR _liver , and SD of the SNR _liver metrics. Results  There were no significant differences in SUV _mean among the various ROIs and VOIs ( p  > 0.05). On the other hand, the lower SUV _SD was obtained by spherical VOI with diameter of 30 mm. The largest SNR _liver was obtained by ROI (30 mm). The SD of SNR _liver with ROI (30 mm) was also the largest, while the lowest SD of SNR _liver was observed for VOI (40 mm). There is a higher correlation coefficient between the patient-dependent parameter of weight and the image quality parameter of SNRliver for both VOI (30 mm) and VOI (40 mm) compared to the ROIs. Conclusion  Our results indicate that SNR _liver measurements are affected by the size and shape of the respective ROIs and VOIs. The spherical VOI with a 40 mm diameter leads to more stable and reproducible SNR measurement in the liver.

Incidental Detection of Radiotracer Uptake in Spindle Cell Lipoma on 18 F-PSMA PET/CT

ABSTRACT

An 84-year-old man underwent 18 F-prostate-specific membrane antigen (PSMA) PET/CT for staging of a newly diagnosed prostate adenocarcinoma. PET/CT revealed high 18 F-PSMA uptake in a thigh mass, which was initially suspected for a metastasis. Histopathology revealed a rare entity of spindle cell lipoma, which should be added to the reported list of neoplasms that can show "false-positive" PSMA uptake during evaluation of patients with prostate carcinoma representing a potential interpretative pitfall.

68Ga-PSMA-11 uptake in tracheal mucus plug - a potential pitfall

Prostate-specific membrane antigen (PSMA) PET/CT is a well-acclaimed imaging modality for prostate cancer (PCa). However, many reports have highlighted PSMA radioligand uptake in a variety of benign tumors and lesions. We report a case of PCa in which ⁶⁸ Ga-PSMA-11 uptake was noted in the tracheal lumen. However, ¹⁸F-PSMA-1007 PET/CT was done on a subsequent day, which demonstrated no abnormal radiotracer uptake or morphological lesion within the tracheal lumen. This case highlights an uncommon finding of PSMA ligand uptake in a tracheal mucus plug (non-prostatic benign uptake), which may be misinterpreted as a false-positive finding.

[68 Ga]Ga-PSMA-11 Small Bowel Uptake in Crohn’s Disease: Revisiting the “Non-specificity” of PSMA Ligands

The rapidly evolving clinical utility of prostate-specific membrane antigen (PSMA) PET/CT as an imaging modality for prostate cancer (PCa) has brought to the forefront a multitude of non-prostatic diseases also exhibiting PSMA radioligand uptake. We report a case of a 71-year-old male with PCa who underwent PSMA PET/CT for recurrence evaluation. The scan demonstrated [68 Ga]Ga-PSMA-11 uptake in the distal ileum. Retrospective enquiry revealed that the patient was a known case of Crohn's disease. This case highlights an uncommon finding of PSMA radioligand uptake in the distal small bowel (non-prostatic benign pathological uptake) in a patient with known Crohn's disease, which may be misinterpreted in the evaluation of PCa.

Metastatic Thyroid Cartilage Lesion from Prostatic Adenocarcinoma on 68Ga-Prostate-Specific Membrane Antigen Positron Emission Tomography-Computed Tomography Scan: Case Series

Prostate cancer usually metastasizes to regional lymph nodes and bone. Laryngeal cartilage metastases are very rare and only few cases have been published so far describing thyroid cartilage metastatic lesions from prostate cancer. Here, we describe 5 cases of carcinoma prostate, 3 staging and 2 follow-up, where ⁶⁸Ga-prostate-specific membrane antigen positron emission tomography/computed tomography (PET/CT) scan revealed multiple skeletal lesions along with thyroid cartilage metastasis. Initially, laryngeal cartilage metastases remain asymptomatic and in later stages patients present with symptoms. These metastatic lesions to thyroid cartilage are rare entities and can often easily be missed on conventional imaging. PET-CT imaging has overcome this diagnostic problem due to its ability to provide for both anatomical and functional imaging.

Ultrafast Photoclick Reaction for Selective 18F-Positron Emission Tomography Tracer Synthesis in Flow

The development of very fast, clean, and selective methods for indirect labeling in PET tracer synthesis is an ongoing challenge. Here we present the development of an ultrafast photoclick method for the synthesis of short-lived ¹⁸F-PET tracers based on the photocycloaddition reaction of 9,10-phenanthrenequinones with electron-rich alkenes. The respective precursors are synthetically easily accessible and can be functionalized with various target groups. Using a flow photo-microreactor, the photoclick reaction can be performed in 60 s, and clinically relevant tracers for prostate cancer and bacterial infection imaging were prepared to demonstrate practicality of the method.

Circulating Tumor Cells Expressing the Prostate Specific Membrane Antigen (PSMA) Indicate Worse Outcome in Primary, Non-Metastatic Triple-Negative Breast Cancer

Background: We analyzed mRNA profiles of prostate cancer related genes in circulating tumor cells (CTCs) of primary, non-metastatic triple-negative breast cancer (TNBC) patients (pts) before and after neoadjuvant chemotherapy to elucidate the potential of prostate cancer targets in this BC subgroup.

Method: Blood from 41 TNBC pts (n = 41 before / 26 after therapy) was analyzed for CTCs applying the AdnaTest EMT-2/Stem Cell Select. Multimarker RT-qPCR allowed the detection of the prostate specific antigen PSA, the prostate specific membrane antigen PSMA, full-length androgen receptor (AR-FL), and AR splice-variant seven (AR-V7).

Results: Before therapy, at least one prostate cancer related gene was detected in 15/41 pts (37%). Notably, in 73% of AR-FL positive cases, AR-V7 was co-expressed. After therapy, CTCs of only one patient harbored prostate cancer related genes. AR-V7+ and PSMA+ CTCs significantly correlated with early relapse (p = 0.041; p = 0.00039) whereas PSMA+ CTCs also associated with a reduced OS (p = 0.0059). This correlation was confirmed for PSMA+ CTCs in univariate (PFS p = 0.002; OS p = 0.015), but not multivariate analysis.

Conclusion: Although CTCs that expressed prostate cancer related genes were eliminated by the given therapy, PSMA+ CTCs significantly identified pts at high risk for relapse. Furthermore, AR inhibition, often discussed for this BC subgroup, might not be successful in the primary setting of the disease since we identified AR-FL+ CTCs together with AR-V7+ CTCs, associated with therapeutic failure.

Incidental Detection of Malignant Melanoma Brain Recurrence on 68Ga-Prostate-Specific Membrane Antigen PET/CT

A 76-year-old man with a prior medical history of resected malignant melanoma of the skull underwent Ga-prostate-specific membrane antigen (PSMA) PET/CT due to rising tumor markers of a known prostate carcinoma. Unexpected high Ga-PSMA brain uptake was encountered around the surgical cavity in the skull with initially no specific structural changes on anatomical imaging. Successive CT and MRI eventually revealed local melanoma brain recurrence at this site. This interesting case demonstrates the diagnostic potential of Ga-PSMA PET/CT imaging for detection of malignant melanoma brain recurrence.

Prostate-specific membrane antigen positron emission tomography in the management of recurrent prostate cancer

INTRODUCTION

There is an unmet clinical need for early, accurate imaging of recurrent prostate cancer to improve patient outcomes. Staging, by conventional bone scintigraphy and CT have become outdated. 68Ga-PSMA PET/CT imaging in this setting has developed rapidly, with widespread International adoption in line with evidence-based guidelines in this group of patients.

SOURCES OF DATA

A PubMed search of English language articles was performed using following keywords: PSMA, PET/CT, biochemical recurrence, prostate cancer. The search revealed 85 articles, of which 75 were original; 70 of these involved use of the most widely available type of PSMA tracer (HBED). The review also relied on the clinical experience of reporting over 1000 PSMA PET/CT studies at a major tertiary referral centre for uro-oncology, with the majority of cases having been performed in the biochemical recurrence setting from 2015 to 2018.

AREAS OF AGREEMENT

68Ga-PSMA PET is a game changer and superior to choline PET and other established tracers which have been used in prostate cancer evaluation. Detection of recurrence at the prostate bed remains challenging due to bladder and urethral tracer accumulation. The main strength of PSMA PET/CT is its ability to identify small (<8 mm) pathological lymph nodes, upstaging nodal status in up to two-thirds of cases. Additionally, PSMA PET/CT, detects bone and bone marrow metastases missed by conventional bone and CT imaging. Thus, PSMA PET/CT has major impact on patient management, with studies reporting overall changes in 39-76% of cases.

AREAS OF CONTROVERSY

Controversy exists regarding patient access and NHS affordability of PSMA PET/CT imaging. Currently, no reimbursement is available under the NHS tariff system. The cost outlay for tertiary hospital linked PET centres ranges from £150-170 K. Large referral volumes, and technical advances in manufacturing process will make this tracer cost neutral and similar to the current funded, but less sensitive, choline PET. Current NICE guidelines for prostate cancer management do not include a recommendation on when PSMA PET/CT should be used and this is likely to remain the case in the next revision, due in 2019.

GROWING POINTS

Although PSMA PET/CT imaging results in significant management change, there is a need for high quality economic evaluation and cost analysis for this modality. Lack of this data will result in poor adoption of this technique and thus limit patient access. Furthermore, it is hoped that future tracers will become even more sensitive and identify disease at earlier thresholds.

AREAS TIMELY FOR DEVELOPING RESEARCH

Well-designed clinical trials with consideration of the health economic benefit of using PSMA PET/CT will be essential to provide a basis for entry into guidelines such as NICE and to provide a rationale for reimbursement.

Radiotheranostics in Cancer Diagnosis and Management

The fundamental foundation for precision medicine is accurate and specific targeting of cancer cells. Advances in the understanding of cancer biology, developments in diagnostic technologies, and expansion of therapeutic options have all contributed to the concept of personalized cancer care. Theranostics is the systematic integration of targeted diagnostics and therapeutics. The theranostic platform includes an imaging component that "sees" the lesions followed by administration of the companion therapy agent that "treats" the same lesions. This strategy leads to enhanced therapy efficacy, manageable adverse events, improved patient outcome, and lower overall costs. Radiotheranostics refers to the use of radionuclides for the paired imaging and therapy agents. Radioiodine is the classic radiotheranostic agent that has been used clinically in management of thyroid diseases for nearly 75 years. More recently there have been major exciting strides in radiotheranostics for neuroendocrine tumors and prostate cancer, among other conditions. Regulatory approval of a number of radiotheranostic pairs is anticipated in the near future. Continued support will be needed in research and development to keep pace with the current momentum in radiotheranostics innovations. Moreover, regulatory and reimbursement agencies need to streamline their requirements for seamless transfer of the radiotheranostic agents from the bench to the bedside. In this review, the concept, history, recent developments, current challenges, and outlook for radiotheranostics in the treatment of patients with cancer will be discussed. ^© RSNA, 2018.

Prostate-specific membrane antigen (PSMA) expression in breast cancer and its metastases

The present study was undertaken to investigate the expression of prostate-specific membrane antigen (PSMA) in normal breast tissues, in cancerous breast tissues and in distant metastases from patients with breast cancer. Immunohistochemical analysis was performed to determine PSMA expression and angiogenic activity using anti-PSMA mAb and anti-CD31 mAb respectively. Immunofluorescence staining was applied to confirm the exact co-localization of PSMA and CD31. We observed different patterns of PSMA expression between normal and cancerous tissues. Normal breast tissues showed PSMA expression only in normal glandular cells. However, primary breast tumors and distant metastases showed PSMA expression in tumor cells and in tumor-associated neovasculature. PSMA score group status in primary breast tumors was significantly associated with histologic type and tumor grade (p = 0.026 and p = 0.004 respectively). Distant metastases showed higher PSMA expression in tumor-associated neovasculature comparing with primary tumors. Moreover, brain tumor-associated neovasculture had significantly higher expression of PSMA comparing with bone tumor-associated neovasculture. The localized binding of PSMA mAb to the neovasculature endothelium was confirmed with the double Immunofluorescence staining. ⁶⁸Ga-PSAM imaging of a patient with metastatic breast cancer showed strong tracer uptake in all known skeletal metastases. To the best of our knowledge, this study is the second one that has assessed PSMA expression in a large number of breast cancer patients. Our findings showed that PSMA is particularly expressed in tumor-associated neovasculature of breast tumors and its distant metastases, thus enhancing the evidence on the potential usefulness of PSMA as a therapeutic vascular target.

Focal MRI-Guided Salvage High-Dose-Rate Brachytherapy in Patients With Radiorecurrent Prostate Cancer

Introduction:

Whole-gland salvage treatment of radiorecurrent prostate cancer has a high rate of severe toxicity. The standard of care in case of a biochemical recurrence is androgen deprivation treatment, which is associated with morbidity and negative effects on quality of life. A salvage treatment with acceptable toxicity might postpone the start of androgen deprivation treatment, might have a positive influence on the patients’ quality of life, and might even be curative. Here, toxicity and biochemical outcome are described after magnetic resonance imaging–guided focal salvage high-dose-rate brachytherapy in patients with radiorecurrent prostate cancer.

Materials and Methods:

Seventeen patients with pathologically proven locally recurrent prostate cancer were treated with focal high-dose-rate brachytherapy in a single 19-Gy fraction using magnetic resonance imaging for treatment guidance. Primary radiotherapy consisted of external beam radiotherapy or low-dose-rate brachytherapy. Tumors were delineated with Ga-68–prostate-specific membrane antigen or F18-choline positron emission tomography in combination with multiparametric magnetic resonance imaging. All patients had a prostate-specific antigen level of less than 10 ng/mL at the time of recurrence and a prostate-specific antigen doubling time of ≥12 months. Toxicity was measured by using the Common Terminology Criteria for Adverse Events version 4.

Results:

Eight of 17 patients had follow-up interval of at least 1 year. At a median follow-up interval of 10 months (range 3-40 months), 1 patient experienced a biochemical recurrence according to the Phoenix criteria, and prostate-specific membrane antigen testing revealed that this was due to a distant nodal metastasis. One patient had a grade 3 urethral stricture at 2 years after treatment.

Conclusion:

Focal salvage high-dose-rate brachytherapy in patients with radiorecurrent prostate cancer showed grade 3 toxicity in 1 of 17 patients and a distant nodal metastasis in another patient. Whether this treatment option leads to cure in a subset of patients or whether it can successfully postpone androgen deprivation treatment needs further investigation.

Development and Validation of a High-Pressure Liquid Chromatography Method for the Determination of Chemical Purity and Radiochemical Purity of a [68Ga]-Labeled Glu-Urea-Lys(Ahx)-HBED-CC (Positron Emission Tomography) Tracer

Background: Prostate-specific membrane antigen (PSMA) has gained high attention as a useful biomarker in the imaging evaluation of prostate cancer with positron emission tomography (PET) during recent years. [68Ga]-labeled Glu-urea-Lys(Ahx)-HBED-CC ([68Ga]-PSMA-HBED-CC) is a novel PSMA inhibitor radiotracer which has demonstrated its suitability in detecting prostate cancer. Preparation conditions may influence the quality and in vivo behavior of this tracer, and no standard procedure for the quality control (QC) is available. The aim of this study was to develop a new rapid and simple high-pressure liquid chromatography method of analysis for the routine QCs of [68Ga]-PSMA-HBED-CC to guarantee the high quality of the radiopharmaceutical product before release. Methods: A stepwise approach was used based on the quality by design concept of the International Conference of Harmonisation Q2 (R1) and Q8 (Pharmaceutical Development) guidelines in accordance with the regulations and requirements of European Association of Nuclear Medicine, Society of Nuclear Medicine, International Atomic Energy Agency, World Health Organization, and Italian Association of Nuclear Medicine and Molecular Imaging. The developed analytical test method was validated because a specific monograph in the pharmacopoeia is not available for [68Ga]-PSMA-HBED-CC. Results: The purity and quality of the radiopharmaceutical obtained according to the proposed method resulted high enough to safely administrate it to patients. An excellent linearity was found between 0.8 and 5 μg/mL, with a detection limit of 0.2 μg/mL. Assay imprecision (% CV) was <2%. Conclusions: The developed method to assess the radiochemical and chemical purity of [68Ga]-PSMA-HBED-CC is rapid, accurate, and reproducible, allowing routinely the use of this PET tracer as a diagnostic tool for imaging prostate cancer and also assuring patient safety.

Targeted Radionuclide Therapy: An Evolution Toward Precision Cancer Treatment

OBJECTIVE

This article reviews recent developments in targeted radionuclide therapy (TRT) approaches directed to malignant liver lesions, bone metastases, neuroendocrine tumors, and castrate-resistant metastatic prostate cancer and discusses challenges and opportunities in this field.

CONCLUSION

TRT has been employed since the first radioiodine thyroid treatment almost 75 years ago. Progress in the understanding of the complex underlying biology of cancer and advances in radiochemistry science, multimodal imaging techniques including the concept of "see and treat" within the framework of theranostics, and universal traction with the notion of precision medicine have all contributed to a resurgence of TRT.

What Medical, Urologic, and Radiation Oncologists Want from Molecular Imaging of Prostate Cancer

As molecular imaging better delineates the state of prostate cancer, clinical management will evolve. The currently licensed imaging modalities are limited by lack of specificity or sensitivity for the extent of cancer and for predicting outcome in response to therapy. Clinicians want molecular imaging that-by being more reliable in tailoring treatment and monitoring response for each patient-will become a key facet of precision medicine, surgery, and radiation therapy. Identifying patients who are candidates for specific or novel treatments is important, but equally important is the finding that a given patient may not be a good candidate for single-modality therapy. This article presents prostate cancer scenarios in which managing clinicians would welcome molecular imaging innovations to help with decision making. The potential role of newer techniques that may help fill this wish list is discussed.

Evaluation of the changing landscape of prostate cancer diagnosis and management from 2005 to 2016

Background

Approaches to prostate cancer (PCa) diagnosis and treatment have evolved significantly over past decades. There has been an increasing focus on minimizing overdiagnosis and overtreatment of clinically insignificant PCa. The objective of this study was to evaluate the changes in the diagnostic approach and initial treatment strategy that has evolved over time in an Australian urological private practice.

Materials and methods

Men with newly diagnosed PCa were identified from the private practice electronic and paper medical records from 2005 to 2016 and data was consolidated into six groups of 2-year intervals. Diagnostic strategy was analyzed with particular reference to the use of multiparametric magnetic resonance imaging (mpMRI) scan and ⁶⁸Ga-prostate specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) scans. National Comprehensive Cancer Network risk group stratification was correlated with initial treatment strategy and compared over time.

Results

Chart review identified 839 men who had a mean age of 65.8 years. In 2011–2012, prebiopsy mpMRI scan was introduced. Its uptake correlated with a decrease in numbers of men diagnosed with low risk cancer (r = -0.80, P = 0.04) and an increase in numbers of men diagnosed with high-risk cancer (r = 0.90, P = 0.01). The use of ⁶⁸Ga-PSMA PET/CT was associated with decreasing use of CT and bone scans performed. Open radical prostatectomy had a declining trend particularly when robotic surgery (robotic assisted radical prostatectomy (RARP)) was introduced. Pelvic lymph node dissections performed progressively decreased. An increased use of luteinizing hormone receptor hormone (LHRH) antagonists was seen in favor of LHRH agonists. Whilst use of high dose rate brachytherapy declined, there was an increased use of low dose rate brachytherapy.

Conclusion

Prebiopsy mpMRI has been associated with an increased proportion of newly diagnosed men having clinically significant PCa. Over time, ⁶⁸Ga-PSMA PET/CT scans, robotic assisted radical prostatectomy (RARP) and LHRH antagonists have increased in use, whilst CT and bone scans, and pelvic lymph node dissections have decreased.

68Ga-PSMA-11 PET/CT in primary staging of prostate cancer: PSA and Gleason score predict the intensity of tracer accumulation in the primary tumour

PURPOSE

Prostate cancer (PC) cells typically show increased expression of prostate-specific membrane antigen (PSMA), which can be visualized by ⁶⁸Ga-PSMA-11 PET/CT. The aim of this study was to assess the intensity of ⁶⁸Ga-PSMA-11 uptake in the primary tumour and metastases in patients with biopsy-proven PC prior to therapy, and to determine whether a correlation exists between the primary tumour-related ⁶⁸Ga-PSMA-11 accumulation and the Gleason score (GS) or prostate-specific antigen (PSA) level.

METHODS

Ninety patients with transrectal ultrasound biopsy-proven PC (GS 6-10; median PSA: 9.7 ng/ml) referred for ⁶⁸Ga-PSMA-11 PET/CT were retrospectively analysed. PET images were analysed visually and semiquantitatively by measuring the maximum standardized uptake value (SUV_max). The SUV_max of the primary tumour and pathologic lesions suspicious for lymphatic or distant metastases were then compared to the physiologic background activity of normal prostate tissue and gluteal muscle. The SUV_max of the primary tumour was assessed in relation to both PSA level and GS.

RESULTS

Eighty-two patients (91.1%) demonstrated pathologic tracer accumulation in the primary tumour that exceeded physiologic tracer uptake in normal prostate tissue (median SUV_max: 12.5 vs. 3.9). Tumours with GS of 6, 7a (3+4) and 7b (4+3) showed significantly lower ⁶⁸Ga-PSMA-11 uptake, with median SUV_max of 5.9, 8.3 and 8.2, respectively, compared to patients with GS >7 (median SUV_max: 21.2; p < 0.001). PC patients with PSA ≥10.0 ng/ml exhibited significantly higher uptake than those with PSA levels <10.0 ng/ml (median SUV_max: 17.6 versus 7.7; p < 0.001). In 24 patients (26.7%), 82 lymph nodes with pathologic tracer accumulation consistent with metastases were detected (median SUV_max: 10.6). Eleven patients (12.2%) revealed 55 pathologic osseous lesions suspicious for bone metastases (median SUV_max: 11.6).

CONCLUSIONS

The GS and PSA level correlated with the intensity of tracer accumulation in the primary tumours of PC patients on ⁶⁸Ga-PSMA-11 PET/CT. As PC tumours with GS 6+7 and patients with PSA values ≤10 ng/ml showed significantly lower ⁶⁸Ga-PSMA-11 uptake, ⁶⁸Ga-PSMA-11 PET/CT should be preferentially applied for primary staging of PC in patients with GS >7 or PSA levels ≥10 ng/ml.

68Ga-PSMA PET/CT imaging in recurrent prostate cancer: Where are we now?

Introduction

Prostate cancer (PCa) is a major health concern worldwide with up to 60% of patients experiencing biochemical relapse after radical treatment. Early diagnosis of PCa recurrence is of high importance for successful salvage therapy. The need for accurate imaging has prompted the introduction of prostate-specific membrane antigen (PSMA)-based radiotracers for positron emission tomography (PET).

Material and methods

In this review we summarized and discussed the results of the studies analyzing the utility of 68Ga-PSMA PET/CT in patients who experienced a biochemical relapse of prostate cancer.

Results

PSMA-based PET scans have been proved to provide a superior diagnostic performance over other modalities for localization of the site of early PCa recurrence. 68Ga-PSMA has been also shown to have a higher sensitivity and specificity than other established PET radiotracers such as radiocholines.

Conclusions

The early studies show promising results and support the use of 68Ga-PSMA for PCa restaging. However, the number of studies concerning the utility of 68Ga-PSMA PET in the context of secondary PCa staging is limited and there is still a considerable scope for further research in this field.

Prostate-Specific Membrane Antigen Uptake in Small Cleaved B-Cell Follicular Non-Hodgkin Lymphoma

A 68-year-old man with treated prostate cancer 3 years earlier and small cleaved B-cell follicular lymphoma diagnosed 1 year prior and monitored clinically with no active intervention ("watch and wait" approach) was referred for Ga-prostate-specific membrane antigen (PSMA) PET/CT with rising prostate-specific antigen level. PET/CT demonstrated diffuse PSMA uptake in the prostate (SUVmax 3.6) and multiple PSMA-avid nonenlarged lymph nodes. Moderate PSMA uptake (SUVmax 4.7) was also noted in an enlarged right inguinal lymph node (SUVmax 4.7), which on core biopsy confirmed small cleaved B-cell follicular lymphoma.

Evaluation of 68 Ga-Glutamate Carboxypeptidase II Ligand Positron Emission Tomography for Clinical Molecular Imaging of Atherosclerotic Plaque Neovascularization

Objective—

Intraplaque neovascularization contributes to the progression and rupture of atherosclerotic lesions. Glutamate carboxypeptidase II (GCPII) is strongly expressed by endothelial cells of tumor neovasculature and plays a major role in hypoxia-induced neovascularization in rodent models of benign diseases. We hypothesized that GCPII expression may play a role in intraplaque neovascularization and may represent a target for imaging of atherosclerotic lesions. The aim of this study was to determine frequency, pattern, and clinical correlates of vessel wall uptake of a 68 Ga-GCPII ligand for positron emission tomographic imaging.

Approach and Results—

Data from 150 patients undergoing 68 Ga-GCPII ligand positron emission tomography were evaluated. Tracer uptake in various arterial segments was analyzed and was compared with calcified plaque burden, cardiovascular risk factors, and immunohistochemistry of carotid specimens. Focal arterial uptake of 68 Ga-GCPII ligand was identified at 5776 sites in 99.3% of patients. The prevalence of uptake sites was highest in the thoracic aorta; 18.4% of lesions with tracer uptake were colocalized with calcified plaque. High injected dose ( P =0.0005) and obesity ( P =0.007) were significantly associated with 68 Ga-GCPII ligand accumulation, but other cardiovascular risk factors showed no association. The number of 68 Ga-GCPII ligand uptake sites was significantly associated with overweight condition ( P =0.0154). Immunohistochemistry did not show GCPII expression. Autoradiographic blocking studies indicated nonspecific tracer binding.

Conclusions—

68 Ga-GCPII ligand positron emission tomography does not identify vascular lesions associated with atherosclerotic risk. Foci of tracer accumulation are likely caused by nonspecific tracer binding and are in part noise-related. Taken together, GCPII may not be a priority target for imaging of atherosclerotic lesions.

Synthesis and preclinical evaluation of an Al18F radiofluorinated GLU-UREA-LYS(AHX)-HBED-CC PSMA ligand

PURPOSE

The aim of this study was to synthesize and preclinically evaluate an 18F-PSMA positron emission tomography (PET) tracer. Prostate-specific membrane antigen (PSMA) specificity, biodistribution, and dosimetry in healthy and tumor-bearing mice were determined.

METHODS

Several conditions for the labeling of 18F-PSMA-11 via 18F-AlF-complexation were screened to study the influence of reaction temperature, peptide amount, ethanol volume, and reaction time. After synthesis optimization, biodistribution and dosimetry studies were performed in C57BL6 mice. For proof of PSMA-specificity, mice were implanted with PSMA-negative (PC3) and PSMA-positive (LNCaP) tumors in contralateral flanks. Static and dynamic microPET/computed tomography (CT) imaging was performed.

RESULTS

Quantitative labeling yields could be achieved with >97 % radiochemical purity. The 18F-PSMA-11 uptake was more than 24-fold higher in PSMA-high LNCaP than in PSMA-low PC3 tumors (18.4 ± 3.3 %ID/g and 0.795 ± 0.260 %ID/g, respectively; p < 4.2e-5). Results were confirmed by ex vivo gamma counter analysis of tissues after the last imaging time point. The highest absorbed dose was reported for the kidneys. The maximum effective dose for an administered activity of 200 MBq was 1.72 mSv.

CONCLUSION

18F-PSMA-11 using direct labeling of chelate-attached peptide with aluminum-fluoride detected PSMA-expressing tumors with high tumor-to-liver ratios. The kidneys were the dose-limiting organs. Even by applying the most stringent dosimetric calculations, injected activities of up to 0.56 GBq are feasible.

Prostate-specific membrane antigen positron emission tomography in prostate cancer: a step toward personalized medicine

PURPOSE OF REVIEW

Increasing attention is being given to personalized medicine in oncology, where therapies are tailored to the particular characteristics of the individual cancer patient. In recent years, there has been greater focus on prostate-specific membrane antigen (PSMA) in prostate cancer (PCa) as a target for imaging and therapy with radionuclides. This review highlights the recent advancements in PSMA positron emission tomography (PET) in PCa during the past year.

RECENT FINDINGS

Several reports on PSMA PET/computed tomography (CT) in PCa patients are demonstrating promising results, especially for detection of biochemical recurrence. F-PSMA PET/CT may be superior to Ga-PSMA PET/CT. The detection rate of PSMA PET is influenced by prostate-specific antigen level. PSMA PET/CT may have a higher detection rate than choline PET/CT. Only a few reports have been published on PSMA PET/magnetic resonance imaging (MRI), and this modality remains to be elucidated further.

SUMMARY

Molecular imaging with PSMA PET is paving the way for personalized medicine in PCa. However, large prospective clinical studies are needed to further evaluate the role of PSMA PET/CT and PET/MRI in the clinical workflow of PCa. PSMA is an excellent target for imaging and therapy with radionuclides, and the 'image and treat' strategy has the potential to become a milestone in the management of PCa patients.

Influence of Androgen Deprivation Therapy on the Uptake of PSMA-Targeted Agents: Emerging Opportunities and Challenges

Prostate-specific membrane antigen (PSMA) is an attractive target for both diagnosis and therapy because of its high expression in the vast majority of prostate cancers. Development of small molecules for targeting PSMA is important for molecular imaging and radionuclide therapy of prostate cancer. Recent evidence implies that androgen-deprivation therapy increase PSMA-ligand uptake in some cases. The reported upregulations in PSMA-ligand uptake after exposure to second-generation antiandrogens such as enzalutamide and abiraterone might disturb PSMA-targeted imaging for staging and response monitoring of patients undergoing treatment with antiandrogen-based drugs. On the other hand, second-generation antiandrogens are emerging as potential endoradio-/chemosensitizers. Therefore, the enhancement of the therapeutic efficiency of PSMA-targeted theranostic methods can be listed as a new capability of antiandrogens. In this manuscript, we will present what is currently known about the mechanism of increasing PSMA uptake following exposure to antiandrogens. In addition, we will discuss whether these above-mentioned antiandrogens could play the role of endoradio-/chemosensitizers in combination with the well-established PSMA-targeted methods for pre-targeting of prostate cancer.

Positron emission tomography in imaging evaluation of staging, restaging, treatment response, and prognosis in prostate cancer

Prostate cancer is a prevalent public health problem worldwide. While imaging has played a major role in this disease, there still remain many challenges and opportunities. Positron emission tomography with various physiologically based radiotracers is fundamentally suited to interrogate this biologically and clinically heterogeneous disease along the course of its natural history. In this article, I review briefly the published evidence for the use of positron emission tomography with 18F-fluorodeoxyglucose, 11C-acetate, and 18F- or 11C-choline in the imaging evaluation of prostate cancer. Although the focus of the article will be on these radiotracers given the accumulated experience with them, but I will also comment on the outlook for the use of other emerging PET radiotracers such as those targeted to the prostate-specific membrane antigen and the amino acid metabolism pathway. It is anticipated that PET will play major role in the evaluation of prostate cancer in the current evidence-based medicine environment. There will also be exciting novel prospects for the use of therapeutic-diagnostic (theransotic) pairs in the management of patients with prostate cancer.

NMR-based metabolomics of prostate cancer: a protagonist in clinical diagnostics

Advances in the application of NMR spectroscopy-based metabolomic profiling of prostate cancer comprises a potential tactic for understanding the impaired biochemical pathways arising due to a disease evolvement and progression. This technique involves qualitative and quantitative estimation of plethora of small molecular weight metabolites of body fluids or tissues using state-of-the-art chemometric methods delivering an important platform for translational research from basic to clinical, to reveal the pathophysiological snapshot in a single step. This review summarizes the present arrays and recent advancements in NMR-based metabolomics and a glimpse of currently used medical imaging tactics, with their role in clinical diagnosis of prostate cancer.

Diagnosis of prostate cancer via nanotechnological approach

Prostate cancer is one of the leading causes of cancer-related deaths among the Caucasian adult males in Europe and the USA. Currently available diagnostic strategies for patients with prostate cancer are invasive and unpleasant and have poor accuracy. Many patients have been overly or underly treated resulting in a controversy regarding the reliability of current conventional diagnostic approaches. This review discusses the state-of-the-art research in the development of novel noninvasive prostate cancer diagnostics using nanotechnology coupled with suggested diagnostic strategies for their clinical implication.

Initial prostate cancer diagnosis and disease staging--the role of choline-PET-CT

An early and correct diagnosis together with accurate staging of prostate cancer is necessary in order to plan the most appropriate treatment strategy. Morphological imaging modalities such as transrectal ultrasonography (TRUS), CT, and MRI can have some limitations regarding their accuracy for primary diagnosis and staging of prostate cancer; for instance, they have limited specificity in differentiating cancer from benign prostatic conditions and, by using size as the only criterion to characterize lymph node metastases, they might not be accurate enough for tumour characterization. In this scenario, PET-CT with (11)C-labelled or (18)F-labelled choline derivatives provides morphological and functional characterization and could overcome the limitations of the conventional imaging techniques. PET-CT is one of the most investigated molecular imaging modalities for prostate cancer diagnosis and staging. Currently, the main investigations on the role of PET-CT in the diagnosis and staging of prostate cancer have been performed on a retrospective basis and this type of analysis might be one of the main reasons why different results regarding its diagnostic accuracy have been reported.