Biphasic ⁶⁸Ga-PSMA-HBED-CC-PET/CT in patients with recurrent and high-risk prostate carcinoma

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Comparison of tracer kinetic models for 68Ga-PSMA-11 PET in intermediate-risk primary prostate cancer patients

BACKGROUND

68Ga-PSMA-11 positron emission tomography enables the detection of primary, recurrent, and metastatic prostate cancer. Regional radiopharmaceutical uptake is generally evaluated in static images and quantified as standard uptake values (SUVs) for clinical decision-making. However, analysis of dynamic images characterizing both tracer uptake and pharmacokinetics may offer added insights into the underlying tissue pathophysiology. This study was undertaken to evaluate the suitability of various kinetic models for 68Ga-PSMA-11 PET analysis. Twenty-three lesions in 18 patients were included in a retrospective kinetic evaluation of 55-min dynamic 68Ga-PSMA-11 pre-prostatectomy PET scans from patients with biopsy-demonstrated intermediate- to high-risk prostate cancer. Three kinetic models-a reversible one-tissue compartment model, an irreversible two-tissue compartment model, and a reversible two-tissue compartment model, were evaluated for their goodness of fit to lesion and normal reference prostate time-activity curves. Kinetic parameters obtained through graphical analysis and tracer kinetic modeling techniques were compared for reference prostate tissue and lesion regions of interest.

RESULTS

Supported by goodness of fit and information loss criteria, the irreversible two-tissue compartment model optimally fit the time-activity curves. Lesions exhibited significant differences in kinetic rate constants (K1, k2, k3, Ki) and semiquantitative measures (SUV and %ID/kg) when compared with reference prostatic tissue. The two-tissue irreversible tracer kinetic model was consistently appropriate across prostatic zones.

CONCLUSIONS

An irreversible tracer kinetic model is appropriate for dynamic analysis of 68Ga-PSMA-11 PET images. Kinetic parameters estimated by Patlak graphical analysis or full compartmental analysis can distinguish tumor from normal prostate tissue.

How to Report PSMA PET

Prostate cancer (PCa) is the most common cancer diagnosed in men in most developed countries and a leading cause of cancer-related morbidity and mortality. Prostate-specific membrane antigen positron emission tomography (PSMA-PET) has become a valuable tool in the staging and assessment of disease recurrence in PCa, and more recently for assessment for treatment eligibility to PSMA radioligand therapy (RLT). Harmonization of PSMA-PET interpretation and synoptic reports are needed to communicate concisely and reproducibly PSMA-PET/CT to referring physicians and to support clinician therapeutic management decisions in various stages of the disease. Uniform image interpretation is also important to provide comparable data between clinical trials and to translate such data from research to daily practice. This review provides an overview of the value of PSMA-PET across the different clinical stages of PCa, discusses published reporting criteria for PSMA-PET, identifies pitfalls in reporting PSMA, and provides recommendations for synoptic reports.

Comparison of Tracer Kinetic Models for 68Ga-PSMA-11 PET in Intermediate Risk Primary Prostate Cancer Patients

BACKGROUND

68Ga-PSMA-11 positron emission tomography enables the detection of primary, recurrent, and metastatic prostate cancer. Regional radiopharmaceutical uptake is generally evaluated in static images and quantified as standard uptake values (SUV) for clinical decision-making. However, analysis of dynamic images characterizing both tracer uptake and pharmacokinetics may offer added insights into the underlying tissue pathophysiology. This study was undertaken to evaluate the suitability of various kinetic models for 68Ga-PSMA-11 PET analysis. Twenty-three lesions in 18 patients were included in a retrospective kinetic evaluation of 55-minute dynamic 68Ga-PSMA-11 pre-prostatectomy PET scans from patients with biopsy-demonstrated intermediate to high-risk prostate cancer. A reversible one-tissue compartment model, irreversible two-tissue compartment model, and a reversible two-tissue compartment model were evaluated for their goodness-of-fit to lesion and normal reference prostate time-activity curves. Kinetic parameters obtained through graphical analysis and tracer kinetic modeling techniques were compared for reference prostate tissue and lesion regions of interest.

RESULTS

Supported by goodness-of-fit and information loss criteria, the irreversible two-tissue compartment model was selected as optimally fitting the time-activity curves. Lesions exhibited significant differences in kinetic rate constants (K1, k2, k3, Ki) and semiquantitative measures (SUV) when compared with reference prostatic tissue. The two-tissue irreversible tracer kinetic model was consistently appropriate across prostatic zones.

CONCLUSIONS

An irreversible tracer kinetic model is appropriate for dynamic analysis of 68Ga-PSMA-11 PET images. Kinetic parameters estimated by Patlak graphical analysis or full compartmental analysis can distinguish tumor from normal prostate tissue.

Combined forced diuresis and late acquisition on [68Ga]Ga-PSMA-11 PET/CT for biochemical recurrent prostate cancer: a clinical practice-oriented study

OBJECTIVES

Increased detection of prostate cancer (PCa) recurrences using [⁶⁸Ga]Ga-PSMA-11 PET/CT has been reported by adding forced diuresis or late-phase imaging to the standard protocol. However, the combination of these procedures in the clinical setting is still not standardized.

METHODS

One hundred prospectively recruited biochemical recurrent PCa patients were restaged with dual-phase [⁶⁸Ga]Ga-PSMA-11 PET/CT from September 2020 to October 2021. All patients received a standard scan (60 min), followed by diuretics (140 min) and a late-phase abdominopelvic scan (180 min). PET readers with low (n = 2), intermediate (n = 2), or high (n = 2) experience rated (i) standard and (ii) standard + forced diuresis late-phase images in a stepwise fashion according to E-PSMA guidelines, scoring their level of confidence. Study endpoints were (i) accuracy against a composite reference standard, (ii) reader's confidence level, and (iii) interobserver agreement.

RESULTS

Forced diuresis late-phase imaging increased the reader's confidence category for local and nodal restaging (both p < 0.0001), and the interobserver agreement in identifying nodal recurrences (from moderate to substantial, p < 0.01). However, it significantly increased diagnostic accuracy exclusively for local uptakes rated by low-experienced readers (from 76.5 to 84%, p = 0.05) and for nodal uptakes rated as uncertain at standard imaging (from 68.1 to 78.5%, p < 0.05). In this framework, SUVmax kinetics resulted in an independent predictor of PCa recurrence compared to standard metrics, potentially guiding the dual-phase PET/CT interpretation.

CONCLUSIONS

The present results do not support the systematic combination of forced diuresis and late-phase imaging in the clinical setting, but allow the identification of patients-, lesions-, and reader-based scenarios that might benefit from it.

KEY POINTS

• Increased detection of prostate cancer recurrences has been reported by adding diuretics administration or an additional late abdominopelvic scan to the standard [⁶⁸Ga]Ga-PSMA-11 PET/CT procedure. • We verified the added value of combined forced diuresis and delayed imaging, showing that this protocol only slightly increases the diagnostic accuracy of [⁶⁸Ga]Ga-PSMA-11 PET/CT, thus not justifying its systematic use in clinics. • However, it can be helpful in specific clinical scenarios, e.g., when PET/CT is reported by low-experienced readers. Moreover, it increased the reader's confidence and the agreement among observers.

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

Background

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

Methods

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

Results

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

Conclusions

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

Supplementary Information

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

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

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

The Role of PSMA PET/CT in the Primary Diagnosis and Follow-Up of Prostate Cancer-A Practical Clinical Review

Simple Summary

The combination of positron emission tomography (PET)-diagnostics with ligands binding to the prostate-specific membrane antigen (PSMA) has been a diagnostic milestone in the situation of biochemical recurrence of prostate cancer and is gaining importance in primary diagnostics, providing a highly specific and sensitive diagnostic method in various clinical situations. However, the clinical application of this method requires a comprehensive knowledge of its advantages and disadvantages, potential pitfalls and influencing factors. This review aims to provide a practical clinical review of the currently available background data on PSMA PET/CT, as well as the clinical implications. Although a large amount of data already exist, a thorough analysis is complicated by study heterogeneity, showing the need for future systematic and prospective research.

Abstract

The importance of PSMA PET/CT in both primary diagnostics and prostate cancer recurrence has grown steadily since its introduction more than a decade ago. Over the past years, a vast amount of data have been published on the diagnostic accuracy and the impact of PSMA PET/CT on patient management. Nevertheless, a large heterogeneity between studies has made reaching a consensus difficult; this review aims to provide a comprehensive clinical review of the available scientific literature, covering the currently known data on physiological and pathological PSMA expression, influencing factors, the differences and pitfalls of various tracers, as well as the clinical implications in initial TNM-staging and in the situation of biochemical recurrence. This review has the objective of providing a practical clinical overview of the advantages and disadvantages of the examination in various clinical situations and the body of knowledge available, as well as open questions still requiring further research.

The differential diagnostic value of dual-phase 18F-DCFPyL PET/CT in prostate carcinoma

OBJECTIVE

Binding of ¹⁸F-DCFPyL at prostate cancer (PC) cells increases over time. The dual-phase protocol may be helpful in separating benign lesions from malignant ones associated with prostate cancer. The purpose of this study was to retrospectively analyze the incremental diagnostic value of ¹⁸F-DCFPyL dual-time imaging in patients with prostate cancer.

METHOD

114 prostate-related malignant lesions and 43 benign lesions in 38 patients with prostate cancer were retrospectively analyzed. Maximum standardized uptake value (SUVmax) for benign and prostate-related malignant lesions were calculated at min 60 and min 120 of PET/CT imaging. In order to calculate SUV ratio, the SUVmax of left gluteus maximus was measured at the same time. The difference of SUVmax metrics and SUV ratio between malignant and benign lesions was statistically analyzed, the cut-off value of ROC curve was calculated, and the diagnostic efficacy of SUVmax index and SUV ratio at two time points was compared.

RESULTS

SUVmax metrics and SUV ratio of early and delayed imaging of PC-related malignant lesions were significantly higher than those of benign lesions (p < 0.05). In terms of individual indicators, the highest accuracy and sensitivity was in the delayed SUV ratio (89.2% and 94.7%), the best specificity was in the early SUVmax (93.0%). When the individual and combined indicators were compared together, the SUV ratio in the delay period still showed the best diagnostic sensitivity and accuracy, and the best specificity were SUVmax early and ▵SUVmax, SUVmax early and RI.

CONCLUSIONS

Uptake of ¹⁸F-DCFPyL increased over time in prostate-associated malignant lesions compared with benign tissue. For single-phase imaging, 2-hour (delayed) imaging has better diagnostic performance. However, the dual-phase imaging (1 and 2 h) are helpful in the differential diagnosis of prostate-associated malignant lesions and benign lesions.

68Ga-PSMA11 PET/CT for biochemically recurrent prostate cancer: Influence of dual-time and PMT- vs SiPM-based detectors

•

⁶⁸Ga-PSMA11 PET/CT showed high detection rates for recurrent prostate cancer.

•

Standard and new generation PET/CT performed equally on a per-patient basis.

•

Delayed imaging revealed no additional lesions.

•

SiPM-based PET/CT identified more prostate cancer lesions.

•

PSMA positivity rate increased with higher PSA levels and higher PSA velocity.

Objectives

⁶⁸Ga-PSMA11 PET/CT is excellent for evaluating biochemically recurrent prostate cancer (BCR PC). Here, we compared the positivity rates of dual-time point imaging using a PET/CT scanner (DMI) with silicon photomultiplier (SiPM) detectors and a PET/CT scanner (D690) with photomultiplier tubes (PMT), in patients with BCR PC.

Methods

Fifty-eight patients were prospectively recruited and randomized to receive scans on DMI followed by D690 or vice-versa. Images from DMI were reconstructed using the block sequential regularized expectation maximization (BSREM) algorithm and images from D690 were reconstructed using ordered subset expectation maximization (OSEM), according to the vendor's recommendations. Two readers independently reviewed all images in randomized order, recorded the number and location of lesions, as well as standardized uptake value (SUV) measurements.

Results

Twenty-eight patients (group A) had DMI as first scanner followed by D690, while 30 patients (group B) underwent scans in reversed order. Mean PSA was 30±112.9 (range 0.3–600.66) ng/mL for group A and 41.5 ± 213.2 (range 0.21–1170) ng/mL for group B (P = 0.796). The positivity rate in group A was 78.6% (22/28 patients) vs. 73.3% (22/30 patients) in group B. Although the performance of the two scanners was equivalent on a per-patient basis, DMI identified 5 additional sites of suspected recurrent disease when used as first scanner. The second scan time point did not reveal additional abnormal uptake.

Conclusions

The delayed time point in ⁶⁸Ga-PSMA11 PET/CT did not show a higher positivity rate. SiPM-based PET/CT identified additional lesions. Further studies with larger cohorts are needed to confirm these results.

Combination of Forced Diuresis with Additional Late Imaging in 68Ga-PSMA-11 PET/CT: Effects on Lesion Visibility and Radiotracer Uptake

Renal excretion of some prostate-specific membrane antigen (PSMA) ligands and consequently increased bladder activity can obscure locally relapsing prostate cancer lesions in PSMA PET/CT. Furthermore, additional late imaging in PSMA PET/CT provides a useful method to clarify uncertain findings. The aim of this retrospective study was to investigate a modified imaging protocol combining late additional imaging with hydration and forced diuresis in individuals undergoing additional late scanning for uncertain lesions or low prostate-specific antigen. Methods: We compared an older protocol with a newer one. In the old protocol, patients undergoing 68Ga-PSMA-11 PET/CT were examined at 90 min after injection, with 1 L of oral hydration beginning at 30 min after injection and 20 mg of furosemide given intravenously at 1 h after injection, followed by additional late imaging at 2.5 h after injection without further preparation. In the new protocol, a second group received the same procedure as before, with an additional 0.5 L of oral hydration and 10 mg of furosemide intravenously 30 min before the late imaging. We examined 132 patients (76 with the old protocol and 56 with the new one) with respect to urinary bladder activity (SUVmean), prostate cancer lesion uptake (SUVmax), and lesion contrast (ratio of tumor SUVmax to bladder SUVmean for local relapses and ratio of tumor SUVmax to gluteal-muscle SUVmean for nonlocal prostate cancer lesions). Results: Bladder activity was significantly greater for the old protocol in the late scans than for the new protocol (ratio of bladder activity at 2.5 h to bladder activity at 1.5 h, 2.33 ± 1.17 vs. 1.37 ± 0.50, P < 0.0001). Increased tumor SUVmax and contrast were seen at 2.5 h compared with 1.5 h (P < 0.0001 for old protocol; P = 0.02 for new protocol). Increased bladder activity for the old protocol resulted in decreased lesion-to-bladder contrast, which was not the case for the new protocol. Tumor-to-background ratios increased at late imaging for both protocols, but the increase was significantly lower for the new protocol. For the old protocol, comparing the 1.5-h to the 2.5-h acquisitions, 4 lesions in 4 patients (4/76 = 5.2% of the cohort) were visible at the postdiuresis 1.5-h acquisition but not at 2.5 h, having been obscured as a result of the higher bladder activity. In the new protocol, 2 of 56 (3.6%) patients had lesions visible only at late imaging, and 2 patients had lesions that could be better discriminated at late imaging. Conclusion: Although the combination of diuretics and hydration can be a useful method to increase the visualization and detectability of locally recurrent prostate cancer in standard 68Ga-PSMA-11 PET/CT, their effects do not sufficiently continue into additional late imaging. Additional diuresis and hydration are recommended to improve the visibility, detection, and diagnostic certainty of local recurrences.

Optimal Time Point for 68Ga-PSMA-11 PET/CT Imaging in the Assessment of Suspected Metastatic Prostate Cancer in the Bladder of Postprostatectomy Patient

ABSTRACT

A 77-year-old man with prostate cancer had prostatectomy and hormonal therapy and underwent pelvic MRI and 68Ga-PSMA-11 PET/CT during clinical follow-up. A pelvic MRI scan showed suspected metastasis along the posterior wall of urinary bladder. The 68Ga-PSMA-11 PET/CT was acquired in a dual-time point fashion, at 60 minutes and 110 minutes postinjection. At 60 minutes postinjection, the known bladder wall lesion showed lower than urine background uptake. On 110 minutes delayed images, the bladder wall lesion showed avid PSMA uptake, much higher than the urine background, increased PSMA uptake by the tumor over time, and improved contrast in the lesion.

Biphasic GA 68-labeled prostate specific membrane antigen-11 positron emission tomography/computed tomography scans in the differential diagnosis and risk stratification of initial primary prostate cancer

Background

This study aimed to assess the value of biphasic GA 68-labeled prostate-specific membrane antigen-11 (⁶⁸Ga-PSMA-11) positron emission tomography/computed tomography (PET/CT) scan in the differential diagnosis and risk stratification of initial primary prostate cancer (PCa).

Methods

A total of 51 patients with PCa (8 low- and intermediate-risk PCa patients and 43 high-risk PCa patients) and 36 patients with benign prostate lesions, who underwent standard whole-body imaging and delayed pelvic imaging of ⁶⁸Ga-PSMA-11 PET/CT, were enrolled in this prospective study. The PET parameters, such as maximum and mean standard uptake value (SUVmax and SUVmean), and maximum and mean standard retention index of PET images were calculated and compared in different prostate lesions. The diagnostic performances of the PET parameters were evaluated by receiver operating characteristic (ROC) curves.

Results

All the PET parameters of PCa participants were significantly higher than those of participants with benign prostate lesions (P<0.001). The SUVmean of delayed imaging had the best performance in the diagnosis of PCa with an area under the curve (AUC) of 0.918 (95% CI: 0.858 to 0.977), the sensitivity of 90.0%, and specificity of 83.3%. The SUVmax and SUVmean of high-risk PCa participants were significantly higher than those of low- and intermediate-risk PCa participants (P<0.005). The SUVmax of standard imaging had the best performance in predicting high-risk PCa with an AUC of 0.890 (95% CI: 0.799 to 0.980), a sensitivity of 76.7%, and a specificity of 100.0%.

Conclusions

The biphasic ⁶⁸Ga-PSMA-11 PET/CT scan had good performance in discriminating prostate cancer from benign prostate diseases. The SUVmean of the prostate lesion at delayed imaging of ⁶⁸Ga-PSMA-11 PET/CT had the best value in the differential diagnosis of PCa, and the SUVmax at standard imaging was most valuable in predicting the risk stratification of PCa.

Impact of the Noise Penalty Factor on Quantification in Bayesian Penalized Likelihood (Q.Clear) Reconstructions of 68Ga-PSMA PET/CT Scans

Functional imaging with ⁶⁸Ga prostate-specific membrane antigen (PSMA) and positron emission tomography (PET) can fulfill an important role in treatment selection and adjustment in prostate cancer. This article focusses on quantitative assessment of ⁶⁸Ga-PSMA-PET. The effect of various parameters on standardized uptake values (SUVs) is explored, and an optimal Bayesian penalized likelihood (BPL) reconstruction is suggested. PET acquisitions of two phantoms consisting of a background compartment and spheres with diameter 4 mm to 37 mm, both filled with solutions of ⁶⁸Ga in water, were performed with a GE Discovery 710 PET/CT scanner. Recovery coefficients (RCs) in multiple reconstructions with varying noise penalty factors and acquisition times were determined and analyzed. Apparent recovery coefficients of spheres with a diameter smaller than 17 mm were significantly lower than those of spheres with a diameter of 17 mm and bigger (p < 0.001) for a tumor-to-background (T/B) ratio of 10:1 and a scan time of 10 min per bed position. With a T/B ratio of 10:1, the four largest spheres exhibit significantly higher RCs than those with a T/B ratio of 20:1 (p < 0.0001). For spheres with a diameter of 8 mm and less, alignment with the voxel grid potentially affects the RC. Evaluation of PET/CT scans using (semi-)quantitative measures such as SUVs should be performed with great caution, as SUVs are influenced by scanning and reconstruction parameters. Based on the evaluation of multiple reconstructions with different β of phantom scans, an intermediate β (600) is suggested as the optimal value for the reconstruction of clinical ⁶⁸Ga-PSMA PET/CT scans, considering that both detectability and reproducibility are relevant.

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

Introduction:

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

Materials and methods:

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

Results:

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

Conclusion:

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

Prostate-Specific Membrane Antigen PET for Assessment of Primary and Recurrent Prostate Cancer with Histopathology as Reference Standard: A Systematic Review and Meta-Analysis

Prostate-specific membrane antigen PET is a promising diagnostic tool in prostate cancer. The gold standard for the detection of prostate tumor and lymph node metastases is histopathology. The aim of the present review was to investigate accuracy measures of ⁶⁸Ga/¹⁸F-labeled prostate-specific membrane antigen PET tracers in primary and recurrent prostate cancer with systematic sector-based histopathology as the reference standard. A systematic literature search was performed and 34 studies were included. Overall, prostate-specific membrane antigen PET showed high specificity, but variable sensitivity to localize known prostate cancer and detect pelvic lymph node metastases.

Performance of [68Ga]Ga-PSMA-11 PET/CT in patients with recurrent prostate cancer after prostatectomy-a multi-centre evaluation of 2533 patients

PURPOSE

To evaluate the performance of [⁶⁸Ga]Ga-PSMA-11 PET/CT in the diagnosis of recurrent prostate cancer (PC) after prostatectomy in a large multicentre cohort.

METHODS

The centres, which contributed to this study, were the departments of nuclear medicine of Heidelberg (Germany), Technical University of Munich (Germany) and Albert Einstein Hospital of São Paulo (Brazil). A total of 2533 patients who were scanned with [⁶⁸Ga]Ga-PSMA-11 PET/CT at 1 h p.i. due to recurrent PC after prostatectomy were included in this retrospective analysis. Exclusion criteria were as follows: patients with untreated primary tumour, previous chemotherapy or Xofigo®; those previously treated with exclusively external beam radiation therapy or HIFU; those referred for PSMA-therapy; and those treated with ADT (including first- and second-generation ADT) within the last 6 months. Potential influences of different factors such as PSA level, PSA doubling-time (PSA_DT), PSA velocity (PSA_Vel), Gleason Score (GSC, including the separate analysis of 7a and 7b), age and amount of injected tracer were evaluated in a multivariable analysis.

RESULTS

The rate of pathologic PET/CT-scans was 43% for PSA ≤ 0.2 ng/ml, 58% for PSA > 0.2 to ≤ 0.5, 72% for PSA > 0.5 to ≤ 1.0 and increased to a maximum of 93% for PSA > 10 ng/ml. A pathological PET/CT was significantly (p = 0.001) associated with PSA level and higher GSC. Amount of injected tracer, age, PSA_DT and PSA_Vel were not associated with a higher probability of a pathological scan.

CONCLUSION

[⁶⁸Ga]Ga-PSMA-11 PET/CT at 1 h p.i. confirmed its high performance in the largest patient cohort yet analysed. Tumour detection showed a clear association with higher PSA and higher GSC. No association was found between a pathological [⁶⁸Ga]Ga-PSMA-11 PET/CT and age, amount of injected tracer, PSA_DT or PSA_Vel.

Dual-Time Point [68Ga]Ga-PSMA-11 PET/CT Hybrid Imaging for Staging and Restaging of Prostate Cancer

Simple Summary

Early diagnosis and tumor characterization of prostate cancer (PCa) are important for accurate treatment. [⁶⁸Ga]Ga-PSMA-11 PET/CT turns out to constitute a major step toward improved diagnostic procedures to detect primary, recurrent, and metastatic PCa. The aim of our study is to evaluate the effect of a second imaging modality for the staging and restaging of PCa by possibly detecting additional PCa lesions due to the well-known increase of PSMA uptake over time. There was a significant increase in tracer uptake on delayed images in comparison to early [⁶⁸Ga]Ga-PSMA-11 PET/CT in our study, but the lesion positivity rate was comparable. However, in a few individual cases, additional delayed scans provided an information advantage in PCa lesion detection. The findings of our study are likely to be of major interest to clinicians as well as to researchers defining the algorithms that are necessary to implement this promising method with its specific tracer into clinical routine.

Abstract

Routine [⁶⁸Ga]Ga-PSMA-11 PET/CT (one hour post-injection) has been shown to accurately detect prostate cancer (PCa) lesions. The goal of this study is to evaluate the benefit of a dual-time point imaging modality for the staging and restaging of PCa patients. Biphasic [⁶⁸Ga]Ga-PSMA-11 PET/CT of 233 patients, who underwent early and late scans (one/three hours post-injection), were retrospectively studied. Tumor uptake and biphasic lesion detection for 215 biochemically recurrent patients previously treated for localized PCa (prostatectomized patients (P-P)/irradiated patients (P-I) and 18 patients suspected of having primary PCa (P-T) were separately evaluated. Late [⁶⁸Ga]Ga-PSMA-11 PET/CT imaging detected 554 PCa lesions in 114 P-P patients, 187 PCa lesions in 33 P-I patients, and 47 PCa lesions in 13 P-T patients. Most patients (106+32 P-P/P-I, 13 P-T) showed no additional PCa lesions. However, 11 PSMA-avid lesions were only detected in delayed images, and 33 lesions were confirmed as malignant by a SUVmax increase. The mean SUVmax of pelvic lymph node metastases was 25% higher (p < 0.001) comparing early and late PET/CT. High positivity rates from routine [⁶⁸Ga]Ga-PSMA-11 PET/CT for the staging and restaging of PCa patients were demonstrated. There was no decisive influence of additional late imaging with PCa lesion detection on therapeutic decisions. However, in a few individual cases, additional delayed scans provided an information advantage in PCa lesion detection due to higher tracer uptake and improved contrast.

Combined Early and Late [68Ga]PSMA-HBED-CC PET Scans Improve Lesion Detectability in Biochemical Recurrence of Prostate Cancer with Low PSA Levels

PURPOSE

Our aim was to evaluate the benefit of early (1 h post-injection (p.i.)) and late (3 h p.i.) [⁶⁸Ga]PSMA-HBED-CC positron emission tomography (PET)/x-ray computed tomography (CT) imaging for detection of biochemical recurrence (BCR) of prostate cancer (PCa).

PROCEDURES

Seventy patients with BCR of the PCa and prostate-specific antigen (PSA) levels of less than 2.0 μg/l were subjected to [⁶⁸Ga]PSMA-HBED-CC PET (mean injected activity 180 MBq). While early imaging contained whole body scans, late imaging was confined to the pelvis and the lower abdomen. Uptake in suspicious lesions was analyzed by peak and maximum standardized uptake values (SUV_peak/max). Tumor-to-background ratios were calculated for all lesions in which the liver served as reference organ. The Wilcoxon matched-pair signed-rank test was used to compare the uptake in suspicious lesions between early and late imaging. Follow-up data were used to validate the existence of the additionally detected lesions.

RESULTS

Forty-four of the 70 patients thus examined were interpreted as PSMA-positive in early and/or late scans while 26 remained without suspicion of PSMA tracer uptake. A total of 70 suspicious lesions were analyzed. Ten tumor-suspicious lesions from seven different patients were better or exclusively visible in the late measurements while three tumor-suspicious lesions from three different patients were better or exclusively visible in the early images. A validation by follow-up data was possible for 11 of these 13 additionally detected lesions. In direct comparison between early and late imaging, the mean SUV_max in PSMA-positive lesions was 74 % higher (p < 0.001) and the mean SUV_peak was 36 % higher (p = 0.001) in the late scans. The SUV_mean in the reference regions was decreasing in the late measurements, whereas the mean TBR increased by a factor of 3 (p < 0.001). Taking confirmed lesions only into account, we estimated a 10 % gain in additionally detected PSMA-positive lesions (7/70) within the patient cohort.

CONCLUSIONS

The time period between injection and data acquisition influences the detection rate of [⁶⁸Ga]PSMA-HBED-CC PET/CT. In biochemical recurrence with low PSA levels, late [⁶⁸Ga]PSMA-HBED-CC PET/CT imaging offers frequent advantages with regard to lesion contrast.

The role of additional late PSMA-ligand PET/CT in the differentiation between lymph node metastases and ganglia

PURPOSE

Differentiating between prostate cancer (PC) lesions and benign structures which exhibit radiotracer uptake in PSMA-ligand PET/CT can be challenging. Additional late imaging has been shown to be a powerful method for the discrimination between PC and non-PC lesions, owing to the increasing tracer uptake of the former. Nevertheless, there are no pre-existing studies which describe the dynamic tracer uptake for ganglia, which this present study aims to address.

METHODS

Fifty consecutive patients with PC who received standard and late ⁶⁸Ga-PSMA-11-PET/CT (by local protocol at 1.5 h "standard" and 2.5 h p.i. "late") underwent retrospective evaluation. All lesions with a tracer uptake above local background indicative for ganglia as well as PC lesions were analysed with regard to their maximum standardised uptake values (SUVmax) and localisation.

RESULTS

Overall, 86 PSMA-positive ganglia were identified in 70% (n = 35) of the patients. Five ganglia exhibited PSMA avidity at late imaging only, and three at standard imaging only. A total of 66 lesions suggestive for PC were detected in 44 patients (88%), of which 45% (n = 30) were morphologically identified as lymph nodes (LN), the remainder being locally recurrent lesions or bone metastases. No solid organ metastases were present in our cohort. At late scanning, 73% of the LN exhibited an increase in SUVmax, whereas 65% of the ganglia exhibited a decreasing or stable SUVmax.

CONCLUSION

Whereas the presence of increasing tracer uptake in potential PC lesions can provide additional data about the likelihood of malignancy, increasing SUVmax alone does not reliably differentiate between ganglia and PC lesions and is a potential diagnostic pitfall. We therefore recommend high-resolution CT to enable morphological characterisation of ganglia.

[Prostate-specific membrane antigen (PSMA)-based diagnostics and treatment of prostate cancer]

BACKGROUND

Since their clinical introduction in 2011, PSMA-PET/CT (PSMA: prostate-specific membrane antigen) as well as PSMA therapy of prostate cancer (PC) have spread rapidly worldwide.

OBJECTIVES

To summarize the current knowledge about both PSMA-PET/CT and PSMA therapy of PC.

METHODS

The knowledge derived from the literature as well as the authors' experiences were collected in this review.

RESULTS

PSMA-PET/CT demonstrates a very high sensitivity and specificity for the detection of recurrent PC as well as for the primary staging of intermediate- and high-risk PC. PSMA therapy shows promising results in third-line treatment for patients with castration-resistant, metastatic PC.

CONCLUSIONS

PSMA-PET/CT is meanwhile established as the gold standard for the detection of recurrent PC and is in the process of assuming the same role for primary staging of intermediate- to high-risk PC. PSMA therapy serves as a promising third-line therapy in an increasing number of centers.

Deep neural network for automatic characterization of lesions on 68Ga-PSMA-11 PET/CT

PURPOSE

This study proposes an automated prostate cancer (PC) lesion characterization method based on the deep neural network to determine tumor burden on ⁶⁸Ga-PSMA-11 PET/CT to potentially facilitate the optimization of PSMA-directed radionuclide therapy.

METHODS

We collected ⁶⁸Ga-PSMA-11 PET/CT images from 193 patients with metastatic PC at three medical centers. For proof-of-concept, we focused on the detection of pelvis bone and lymph node lesions. A deep neural network (triple-combining 2.5D U-Net) was developed for the automated characterization of these lesions. The proposed method simultaneously extracts features from axial, coronal, and sagittal planes, which mimics the workflow of physicians and reduces computational and memory requirements.

RESULTS

Among all the labeled lesions, the network achieved 99% precision, 99% recall, and an F1 score of 99% on bone lesion detection and 94%, precision 89% recall, and an F1 score of 92% on lymph node lesion detection. The segmentation accuracy is lower than the detection. The performance of the network was correlated with the amount of training data.

CONCLUSION

We developed a deep neural network to characterize automatically the PC lesions on ⁶⁸Ga-PSMA-11 PET/CT. The preliminary test within the pelvic area confirms the potential of deep learning methods. Increasing the amount of training data should further enhance the performance of the proposed method and may ultimately allow whole-body assessments.

Contribution of 5th minute and 2nd hour images to standard imaging in (68Ga)PSMA 11 PET/CT

OBJECTIVE

To investigate the superiority or contribution of 5th minute pelvic and 2nd hour whole body Gallium68-prostate-specific membrane antigen-HBED-CC [(⁶⁸Ga)PSMA 11] Positron Emission Tomography/Computed Tomography (PET/CT) images to 1st hour imaging in patients with prostate cancer (PCa).

MATERIALS AND METHODS

A total of 63 patients diagnosed with PCa who underwent (⁶⁸Ga)PSMA 11 PET/CT between April 2019 and June 2019 and who had 5th minute and 1st and 2nd hour images were included in the study. Early (5th minute) pelvic region and 1st and 2nd hour full body images were obtained from all patients. The regions of interest (ROI) were drawn from the background tissues and the physiological uptake sites in a way to include the same lesions from primary and metastatic lesions in all three imagings, and SUVmax values, and tumor-background ratio (TBR) were calculated.

RESULTS

The mean age of the patients was 69.81 ± 8.78 (min/max: 51/91) years. In the 5th minute images, prostate gland and bed were easier to evaluate, because of low bladder activity. However, lymph node evaluation was more difficult due to high vascular activity. In the prostate gland, lymph nodes and bone metastases, both SUVmax values and TBR rates increased with time from the 5th minute (p < 0.001). At the 2nd hour, some lesions became more visible, while decreased activity was observed in some lesions. However, none of the patients required a change in the stage or treatment.

CONCLUSION

In conclusion, the 5th minute pelvic images in (⁶⁸Ga)PSMA 11 PET/CT were helpful in visual evaluation of the prostate gland and bed, while 2nd hour images showed high SUVmax and TBR rates in malignant lesions. As the SUVmax values of benign lesions were found to be lower in the 2nd hour, when compared to the 1st hour, it was thought that the 2nd hour imaging could be used in the additional imaging for suspicious lesions without the need for very long waiting times.

68Ga-PSMA-11 PET/CT in patients with recurrent prostate cancer-a modified protocol compared with the common protocol

PURPOSE

⁶⁸Ga-PSMA-11 PET/CT is commonly performed at 1 h post injection (p.i.). However, various publications have demonstrated that most prostate cancer (PC) lesions exhibit higher contrast at later imaging. The aim of this study was to compare the "common" protocol of ⁶⁸Ga-PSMA-11 PET/CT with a modified protocol.

METHODS

In 2017, we used the following scanning protocol for ⁶⁸Ga-PSMA-11 PET/CT in patients with recurrent PC: acquisition at 1 h p.i. without further preparations. From 2018, all scans were conducted at 1.5 h p.i. In addition, patients were orally hydrated with 1 L of water 0.5 h p.i. and were injected with 20 mg of furosemide 1 h p.i. Both protocols including 112 patients (2017) and 156 (modified protocol in 2018) were retrospectively compared. Rates of pathologic scans, maximum standardized uptake values (SUVmax), and tumor contrast (ratio lesion-SUVmax/background-SUVmean) as well as average standardized uptake values (SUVmean) of urinary bladder were analyzed.

RESULTS

Both tumor contrast and tracer uptake were significantly (p < 0.001) higher in the novel protocol. Although statistically not significant, the rates of pathologic scans were also higher in the modified protocol: 76.3% vs. 68.8% for all PSA values including 38.9% vs. 25.0% for PSA < 0.5 ng/ml and 60.0% vs. 56.7% for PSA > 0.5-≤ 2.0 ng/ml. Average SUVmean of the urinary bladder was significantly (p < 0.001) lower with the modified protocol.

CONCLUSIONS

The modified protocol, which includes a combination of delayed image acquisition at 1.5 h p.i., hydration, and furosemide resulted in higher tumor contrast and seems to have the potential to increase the rates of pathological scans, especially at low PSA levels.

The "question-mark" MR anatomy of the cervico-thoracic ganglia complex: can it help to avoid mistaking it for a malignant lesion on 68Ga-PSMA-11 PET/MR?

Background

Detectable uptake of ⁶⁸Ga-PSMA-ligands in sympathetic ganglia may potentially lead to mistaking them for malignant lesions. Our aim was to investigate the anatomy of cervico-thoracic-ganglia-complex (CTG-C) in the MR part of multimodal ⁶⁸Ga-PSMA-11 PET/MR imaging, in view of PET factors hindering its proper identification.

Patients and methods

In 106 patients, 212 sites of the CTG-C were retrospectively reviewed to assess the radiotracer uptake (SUV_max), size, shape, position, symmetry of location and visual uptake intensity. Asymmetry of PSMA-ligand uptake and increased uptake were regarded as risk factors of malignancy.

Results

In 66.0% left (L) and 53.8% right (R) CTG-C we noticed configurations, resembling the shape of an exclamation-mark, a question-mark, or its part (called “typical”). Tumor-like CTG-C shapes (oval, binodular or longitudinal) were detected in 28.3% L-CTG-C and in 40.6% R-CTG-C. When visual assessment of PET suggested malignancy, the recognition of “typical” shape of underlying CTG-C on MR generated a rise in the accuracy of their proper identification (from 34.4% to 75%, χ2(1) = 70.4; p < 0.001). Recognizing the shape of the CTG-C as “typical” in MR allowed us to classify as “not-suspicious” 61.9% of all CTG-C which were treated as “suspicious” after sole PET assessment.

Conclusions

The characteristic shape of cervico-thoracic-ganglia-complex (resembling a question-mark, or its part) helps in proper recognition of CTG-C on multimodal whole-body ⁶⁸Ga-PSMA-ligand PET/MR imaging, when detectable uptake might lead to considering pathology.

Dynamic patterns of [68Ga]Ga-PSMA-11 uptake in recurrent prostate cancer lesions

PURPOSE

Dual-time point PET/CT scanning with [⁶⁸Ga]Ga-PSMA-11 in the diagnosis of prostate cancer (PC) has been advanced as a method to increase detection of PC lesions, particularly at early stages of biochemical recurrence and as a potential means to aid the discrimination between benign and pathological prostate-specific membrane antigen (PSMA) uptake. However, the assumption that all PC lesions uniformly exhibit increasing tracer uptake at delayed imaging has not yet been investigated, which this present study aims to address.

METHODS

One hundred consecutive patients with biochemically recurrent PC who received standard and late [⁶⁸Ga]Ga-PSMA-11 PET/CT (by local protocol at 1.5 h "standard" and 2.5 h p.i. "late") underwent retrospective evaluation. All lesions with a tracer uptake above local background were analysed with regard to their maximum standardised uptake values at standard and late images (SUVmax) and characterised according to their morphological characteristics.

RESULTS

Seventy-nine of 100 patients had PSMA-positive scans, in whom a total of 185 individual PSMA-positive lesions were identified. These were morphologically characterised as bone lesions (n = 48), solid organ lesions (n = 3), lymph node (LN) lesions (n = 78) and locally recurrent lesions in the prostatic fossa or seminal vesicles (n = 56). The relative uptake between standard and late imaging was considered; all lesions classified as local recurrence presented with increasing (86%) or stable patterns of tracer uptake (14%). In contrast, only 58% of bone lesions exhibited increasing tracer uptake, with 21% exhibiting a stable pattern and 21% exhibiting a decreasing tracer uptake at late imaging.

CONCLUSION

A heterogeneous pattern of dynamic tracer uptake was observed, with a largely increasing pattern observed for locally recurrent lesions and lymph nodes and a significant proportion of bone lesions exhibiting decreasing tracer uptake. The results are of significance not only in the imaging and identification of PC lesions, but they also have implications for PSMA-directed ligand therapy.

Gallium-68 prostate-specific membrane antigen positron emission tomography/computed tomography compared with diagnostic computed tomography in relapsed prostate cancer

The aim of this study was to evaluate if prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) has a higher detection rate compared to standard contrast CT imaging for patients with a rising prostate-specific antigen (PSA) following definitive treatment (i.e., curative radical prostatectomy, radiotherapy, and brachytherapy) for prostate cancer in a private hospital setting. A retrospective single-site clinical audit was conducted on 150 PSMA PET/CT scans done for patients with a rising PSA after definitive treatment for prostate cancer. All studies were performed using I and T Ga-68 PSMA produced on a Scintomics radiopharmaceutical unit (Munich). All scans were performed on a GE 710 PET/CT scanner. All studies were compared to standard CT and other imaging. Of the 150 patients who had a ⁶⁸Gallium (Ga)-PSMA PET/CT for a rise in their PSA levels, 102/150 (68%) of patients had PSMA-avid scans compared to the conventional imaging group which had an overall detection rate of 42% (63/150). The rates of detection were 100%, 90%, 92%, 67%, and 25% at PSA levels of >10 μg/L, 5–10 μg/L, >1.5 μg/L, 0.5–1.5 μg/L, and <0.5 μg/L, respectively. PSMA PET/CT also solely picked up 39/102 (38%) of prostate cancer relapses compared to the conventional imaging group. In our study of 150 patients with biochemical recurrence of prostate cancer, ⁶⁸Ga-PSMA PET/CT demonstrated a superior detection rate (P < 0.05) compared to conventional imaging, including patients with low PSA levels (<0.5 μg/L).

Performance of [68Ga] Ga-PSMA 11 PET for detecting prostate cancer in the lymph nodes before salvage lymph node dissection: a systematic review and meta-analysis

BACKGROUND

Salvage lymph node dissection (sLND) for nodal recurrence in prostate cancer (PCa) patients with biochemical recurrence (BCR) is still not recommended in current guidelines, because of the diagnostic inaccuracy of current conventional imaging. To assess the performance of [⁶⁸Ga] Ga-prostate-specific membrane antigen conjugate 11 positron emission tomography (PSMA-PET) in detecting PCa lymph node metastasis using pathologic confirmation through sLND.

METHODS

Literature search was conducted using the MEDLINE, SCOPUS, Web of Science, and Cochrane Library on November 11th, 2018 to identify the eligible studies. Studies were eligible if they investigated the diagnostic performance of PSMA-PET before sLND in PCa patients with BCR and reported the number of true positive, false positive, false negative, and true negative on a lesion-based and/or field-based analyses to compare with histopathologic findings in sLND specimens.

RESULTS

Fourteen studies published between 2015 and 2018 comprising 462 patients were selected in this systematic review and meta-analysis. The positive predictive value of PSMA-PET before sLND on a patient-based analysis ranged between 0.70 and 0.93. The pooled sensitivity using lesion-based and field-based analyses were 0.84 (95%CI: 0.61-0.95) and 0.82 (95%CI: 0.72-0.89), respectively. The pooled specificity using lesion-based and field-based analyses were 0.97 (95%CI: 0.95-0.99) and 0.95 (95%CI: 0.70-0.99), respectively. The diagnostic odds ratio using lesion-based and field-based analyses were 189 (95%CI: 39-920) and 82 (95%CI: 8-832), respectively.

CONCLUSIONS

PSMA-PET before sLND provided highly accurate performance with clinically relevant high positive and negative predictive values for detecting lymph node disease in patients with BCR after local treatment with curative intent for PCa. PSMA-PET can identify the patients who are likely to benefit from sLND and possibly direct to lesion or region-based dissection.

Gallium-68 Prostate-specific Membrane Antigen Positron Emission Tomography in Advanced Prostate Cancer-Updated Diagnostic Utility, Sensitivity, Specificity, and Distribution of Prostate-specific Membrane Antigen-avid Lesions: A Systematic Review and Meta-analysis

CONTEXT

Accurate staging of high-risk localised, advanced, and metastatic prostate cancer is becoming increasingly more important in guiding local and systemic treatment. Gallium-68 prostate-specific membrane antigen (PSMA) positron emission tomography (PET) has increasingly been utilised globally to assess the local and metastatic burden of prostate cancer, typically in biochemically recurrent or advanced disease. Following our previous meta-analysis, a high-volume series has been reported highlighting the utility of ⁶⁸Ga-PSMA PET in this setting.

OBJECTIVE

To perform a systematic review and meta-analysis to update reported predictors of positive ⁶⁸Ga-PSMA PET according to prior therapy and proportion of positivity in various anatomical locations with sensitivity and specificity profiles.

EVIDENCE ACQUISITION

We performed critical reviews of MEDLINE, EMBASE, ScienceDirect, Cochrane Libraries, and Web of Science databases in July 2018 according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement. Quality assessment was performed using Quality Assessment if Diagnostic Accuracy Studies-2 tool. Meta-analyses of proportions were performed using a random-effect model. Summary sensitivity and specificity values were obtained by fitting bivariate hierarchical regression models.

EVIDENCE SYNTHESIS

A total of 37 articles including 4790 patients were analysed. For patients with biochemical recurrence, positive ⁶⁸Ga-PSMA PET scans increased with higher pre-PET prostate-specific antigen (PSA) levels. For PSA categories 0-0.19, 0.2-0.49, 0.5-0.99, 1-1.99, and ≥2ng/ml, the percentages of positive scans were 33%, 45%, 59%, 75%, and 95%, respectively. No significant differences in positivity were noted between Gleason sums ≤7 and ≥8. Significant differences in positivity after biochemical recurrence in the prostate bed were noted between radical prostatectomy (22%) and radiotherapy (52%) patients. On per-node analysis, high sensitivity (75%) and specificity (99%) were observed.

CONCLUSIONS

Ga-68-PSMA PET improves detection of metastases with biochemical recurrence, particularly at low pre-PET PSA levels of >0.2ng/ml (33%) and 0.2-0.5ng/ml (45%). Ga-68-PSMA-PET produces favourable sensitivity and specificity profiles on meta-analysis of pooled data. This analysis highlights different anatomic patterns of metastatic spread according to PSMA PET in the primary and biochemically recurrent settings.

PATIENT SUMMARY

Gallium-68 prostate-specific membrane antigen positron emission tomography is now an established imaging technique that has been developed in response to inadequacies in standard of care imaging modalities to improve the detection of metastatic disease in prostate cancer, particularly in the setting of disease recurrence. To date, this imaging modality in the setting of primary staging is controversial, given the paucity of data. In light of the growing body of evidence, we summarised the data to date to provide clinicians with an overview of this imaging modality.

Celiac ganglia: can they be misinterpreted on multimodal 68Ga-PSMA-11 PET/MR?

Objective

The objective of this study was to investigate the morphologic features and ⁶⁸Ga-prostate-specific membrane antigen (PSMA)-11 avidity of celiac ganglia (CG) on multimodal PET/MRI.

Materials and methods

⁶⁸Ga-PSMA-11 whole-body PET/MR examinations in 120 patients, referred for staging or follow-up of prostate cancer, were retrospectively reviewed to investigate the radiotracer uptake [maximum standardized uptake value (SUV_max)] and morphologic features (size, shape, location) of CG. Nodular, oval and longitudinal nodular, thick or with oval parts shapes of CG were regarded as mistakable with lymph nodes, whereas linear and longitudinal shapes were considered as not mistakable.

Results

On MR scans, CG were visible in 98% (117/120) on both sides and in two patients only on the left side. Mistakable CG shape was detected in 69% (83/120) of patients on both or at least one side. The left CG were thicker (4±1.4 mm; range: 1.5–7.5 mm) than the right ones (3±1.3 mm; range: 0.5–7 mm). Mean SUV_max was 2.51±1.17 (range: 0.02–5.48) in the left CG and 2.23±1.22 (range: 0.02–5.91) in the right CG. Increased ⁶⁸Ga-PSMA-11 uptake, SUV_max at least 2, was detected in 75% (90/120), and both – erroneous shape and elevated ⁶⁸Ga-PSMA-ligand uptake – was observed in 55% (66/120) of all patients on both sides or at least one side.

Conclusion

Frequently observed, the nodular, oval and longitudinal (nodular, thick or with oval parts) shape of CG, especially of the thicker left CG, on MR scans may cause mistaking them for lymph nodes, even abnormal or metastatic. On whole-body PET/MRI, evident and sometimes high ⁶⁸Ga-PSMA-11 uptake in CG increases the risk of a misinterpretation of them as metastases.

68Ga-PSMA PET/CT and PET/MRI in high-risk prostate cancer patients

Treatment of high-risk prostate cancer (HRPCa) is challenging. Local staging and metastatic evaluation are important for the patient management. Recently, prostate-specific membrane antigen (PSMA)-based imaging modalities such as PSMA PET/CT and PET/MRI have received significant attention for detection of recurrent prostate cancer sites with elevated prostate-specific antigen levels, after therapy. Current evidence suggests that these imaging modalities may also have a role for the management of patients with HRPCa. In this review, we discuss PSMA-based imaging modalities in the management of patients with HRPCa.

Current status of theranostics in prostate cancer

The aim of this review is to report on the current status of prostate-specific membrane antigen (PSMA)-directed theranostics in prostate cancer (PC) patients. The value of 68Ga-PSMA-directed PET imaging as a diagnostic procedure for primary and recurrent PC as well as the role of evolving PSMA radioligand therapy (PRLT) in castration-resistant (CR)PC is assessed. The most eminent data from mostly retrospective studies currently available on theranostics of prostate cancer are discussed. The current knowledge on 68Ga-PSMA PET/CT implicates that primary staging with PET/CT is meaningful in patients with high-risk PC and that the combination with pelvic multi parametric (mp)MR (or PET/mpMR) reaches the highest impact on patient management. There may be a place for 68Ga-PSMA PET/CT in intermediate-risk PC patients as well, however, only a few data are available at the moment. In secondary staging for local recurrence, 68Ga-PSMA PET/mpMR is superior to PET/CT, whereas for distant recurrence, PET/CT has equivalent results and is faster and cheaper compared to PET/mpMR. 68Ga-PSMA PET/CT is superior to 18F / 11Choline PET/CT in primary staging as well as in secondary staging. In patients with biochemical relapse, PET/CT positivity is directly associated with prostate-specific antigen (PSA) increase and amounts to roughly 50% when PSA is raised to ≤0.5 ng/ml and to ≥90% above 1 ng/ml. Significant clinical results have so far been achieved with the subsequent use of radiolabeled PSMA ligands in the treatment of CRPC. Accumulated activities of 30 to 50 GBq of 177Lu-PSMA ligands seem to be clinically safe with biochemical response and PERCIST/RECIST response in around 75% of patients along with xerostomia in 5-10% of patients as the only notable side effect. On the basis of the current literature, we conclude that PSMA-directed theranostics do have a major clinical impact in diagnosis and therapy of PC patients. We recommend that 68Ga-PSMA PET/CT should be performed in primary staging together with pelvic mpMR in high-risk patients and in all patients for secondary staging, and that PSMA-directed therapy is a potent strategy in CRPC patients when other treatment options have failed. The combination of PSMA-directed therapy with existing therapy modalities (such as 223Ra-chloride or androgen deprivation therapy) has to be explored, and prospective clinical multicenter trials with theranostics are warranted.

PSA levels, PSA doubling time, Gleason score and prior therapy cannot predict measured uptake of [68Ga]PSMA-HBED-CC lesion uptake in recurrent/metastatic prostate cancer

Aim: To assess whether clinical prostate cancer (PCA) related factors and therapy status can predict the degree of tracer uptake on [68Ga]PSMA-HBED-CC PET/CT.

Materials & methods: We retrospectively studied 124 patients with recurrent an/or metastatic PCA who underwent [68Ga]PSMAHBED-CC PET/CT. The maximum standardized uptake value (SUVmax) was determined in the prostate bed as well as in three size categories (≤ 5 mm, > 5–15 mm, > 15 mm) in pelvic lymph node, extrapelvic lymph node, bone and visceral metastases.

Results: Significant positive correlations between lesion size and SUVmax were found in pelvic lymph node metastases > 5 -≤15 mm (Spearmans rho = 0.502, p = 0.002) as well as in extrapelvic lymph node metastases5 mm (rho = 0.314, p = 0.033) and > 5 ≤-15 mm (rho = 0.614, p < 0.001). SUVmax tended to be higher in the largest diameter category in each anatomic station than in the middle and lower categories. We were unable to find evidence for a relationship between SUVmax and PSA, PSAdt, Gleason score, androgen deprivation therapy, radiation therapy or chemotherapy status.

Conclusion: Measured tracer uptake in [68Ga]PSMA-HBED-CC PET/CT in patients with recurrent/metastasized prostate cancer is significantly influenced by lesion size as a result of partial volume effects in the very small lesions. Clinical indicators of aggressive prostate cancer behaviour such as PSA levels, PSA doubling time or the Gleason score of the primary tumour, as well as the androgen deprivation therapy, radiation therapy or chemotherapy status are not related to measured tracer uptake.

68 Ga-PSMA PET/CT for the detection of bone metastases in prostate cancer: a systematic review of the published literature

BACKGROUND

68 Ga-labelled prostate-specific membrane antigen (PSMA) is a promising PET ligand for the detection of prostate cancer. Little attention has been given to the ability of 68 Ga-PSMA PET/CT to detect malignant bone lesions and whether this approach is superior to existing bone imaging modalities.

AIM

To review the existing data of 68 Ga-PSMA PET/CT for the diagnosis of bone metastases in prostate cancer.

METHODS

Systematic review of the peer-reviewed literature.

RESULTS

Among 1858 papers in the original search, 37 papers were included in the analysis (six case reports and 31 case series). The vast majority of the studies were low-level evidence studies. Most studies presented data on detection rates without a reference standard. All but two studies were of a retrospective nature. Several cohort studies showed bone metastasis in 5-60% of patients with prostate cancer, including in patients with very low-PSA values. For primary staging, 68 Ga-PSMA PET/CT outperformed bone scans, while the superiority of 68 Ga-PSMA PET/CT compared with bone scans with respect to biochemical recurrence and metastatic castration-resistant prostate cancer (mCRPC) remains to be demonstrated.

CONCLUSION

68 Ga-PSMA PET/CT has shown to be a promising technique for use in prostate cancer. 68 Ga-PSMA PET/CT shows more lesions than bone scans, but data on diagnostic performance are very limited and indicate improved diagnostic performance in primary staging but not in mCRPC. Properly designed studies are needed to clarify the diagnostic performance of 68 Ga-PSMA PET/CT as well as its superiority over existing methods before 68 Ga-PSMA PET/CT can be routinely used for bone imaging.

Why Targeting PSMA Is a Game Changer in the Management of Prostate Cancer

Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein that is highly expressed on prostate adenocarcinomas, exhibits only limited expression in benign and extraprostatic tissues, and thus represents an ideal target for the diagnosis and management of prostate cancer. Since its discovery over 30 y ago, significant effort has been made to develop clinical technology targeting PSMA. The last 5 y have seen an explosion of development of new agents targeting PSMA for diagnostic and therapeutic use. Imaging agents targeting PSMA have been developed for SPECT and PET platforms. PSMA PET imaging appears to outperform traditional imaging in the high-risk localized-disease state, in patients with biochemical recurrence after treatment, and in advanced disease. To date, most of the reported clinical studies of therapeutic agents have used PSMA-targeted radiometals to deliver β-radiation to metastatic disease sites, with ¹⁷⁷Lu being the most widely investigated therapeutic radioisotope. Studies of both antibodies and small-molecule agents have been published and have demonstrated encouraging results. Safety appears generally limited to mild transient bone marrow toxicity and xerostomia because of uptake of the small-molecule agents in the salivary glands. Radiologic responses can be dramatic, and decreases in pain have been observed. The effect on overall survival, however, has yet to be demonstrated.

68Ga-PSMA PET/CT in prostate cancer

Positron emission tomography/computed tomography (PET/CT) with ⁶⁸Ga-PSMA is a non-invasive diagnostic technique to image prostate cancer with increased prostate-specific membrane antigen (PSMA) expression. PSMA is a transmembrane protein present in all prostatic tissues. Increased PSMA expression is seen in several malignancies, although prostate cancer is the tumour where it presents higher concentrations. Almost all prostate adenocarcinomas show PSMA expression in most of lesions, primary and metastatic. Immunohistochemistry has demonstrated that the expression of PSMA increases in patients with de-differentiated, metastatic or hormone-refractory tumours. Moreover, the expression level of PSMA has a prognostic value for disease outcome. PET measures the three-dimensional distribution of ⁶⁸Ga-PSMA, producing semi-quantitative images that allow for non-invasive assessment of PSMA expression.

Performance of 68Ga-PSMA PET/CT for Prostate Cancer Management at Initial Staging and Time of Biochemical Recurrence

PURPOSE OF THE REVIEW

Recently introduced Gallium-68 labeled PSMA-ligands such as HBED-CC (⁶⁸Ga-PSMA) have shown promise for unmet diagnostic needs in prostate cancer.

RECENT FINDINGS

⁶⁸Ga-PSMA has demonstrated improved detection rates and specificity for prostate cancer compared to standard imaging approaches. In the setting of primary disease, ⁶⁸Ga-PSMA appears to preferentially identify treatment-relevant intermediate and high-risk prostate cancer. There is also a growing evidence that ⁶⁸Ga-PSMA positron emission tomography (PET) outperforms alternative conventional imaging methods including choline-based radiotracers for the localization of disease sites at biochemical recurrence, particularly at lower prostate-specific antigen (PSA) levels (< 1 ng/mL). However, the majority of published work lacks rigorous verification of imaging results. ⁶⁸Ga-PSMA offers significant promise for both, primary disease and biochemically recurrent prostate cancer. The evidence base to support ⁶⁸Ga-PSMA is however still underdeveloped, and more rigorous studies substantiating efficacy are needed.

Validation of a [Al18F]PSMA-11 preparation for clinical applications

Imaging prostate-specific membrane antigen (PSMA) using positron emission tomography (PET) has been presented so far as the most sensitive and specific with regard to prostate cancer detection, in particular in high-risk prostate cancer patients. Currently, it mainly features Gallium-68 (⁶⁸Ga) labeled PSMA ligands, notably [⁶⁸Ga]Glu-urea-Lys(Ahx)-HBED-CC ([⁶⁸Ga]-PSMA-11) and [⁶⁸Ga]DOTAGA-FFK (Sub-KuE termed ([⁶⁸Ga]PSMA-I&T). However, ⁶⁸Ga has several shortcomings as radionuclide including a short half-life and non-ideal energies. This has motivated consideration of ¹⁸F-labeled analogues for PET imaging of prostate cancer. Here, we describe a simple synthesis and validation of a fluorine-18 labeled Glu-urea-Lys(Ahx)-HBED-CC ([Al¹⁸F]PSMA-11) for nuclear medicine applications. An efficient method for preparation of [Al¹⁸F]PSMA-11 was developed and validated (according to Pharm Eur) for routinely clinical applications. [Al¹⁸F]PSMA-11 was reproducibly obtained in radiochemical yields of 84 ± 6% (n = 15) and > 98% radiochemical purity using an improved one-step radiofluorination in aqueous solution. The total (production/preparation) time, including purification, pharmacological formulation of the isolated product and the quality control of the injectable solution was less than 60min. The [Al¹⁸F]PSMA-11 was stable over 4h in 1% EtOH/saline selected as injection solution. The solution was sterile, non-pyrogenic and ready for clinical applications after sterile filtration through a 0.22µm membrane filter under sterile conditions. In addition, [Al¹⁸F]PSMA-11 exhibited higher uptake and retention in PMSA-expressing LNCap prostate cells as compared to its clinically established ⁶⁸Ga-labeled analogues [⁶⁸Ga]PSMA-11 and [⁶⁸Ga]PSMA-I&T as well as to [⁶⁸Ga]NOTA-Bn-PSMA. The simple and fast preparation of [Al¹⁸F]PSMA-11 combined with its favorable pharmacological properties warrant its translation to a clinical setting.

CONCLUSION

The facile and high-yielding radiosynthesis of [Al¹⁸F]PSMA-11as well as its promising in vitro and in-vivo characteristics makes it worthy of clinical development for PET imaging of prostate cancer.

Pearls and pitfalls in clinical interpretation of prostate-specific membrane antigen (PSMA)-targeted PET imaging

BACKGROUND

The rapidly expanding clinical adaptation of prostate-specific membrane antigen (PSMA)-targeted PET imaging in the evaluation of patients with prostate cancer has placed an increasing onus on understanding both the potential pearls of interpretation as well as limitations of this new technique. As with any new molecular imaging modality, accurate characterization of abnormalities on PSMA-targeted PET imaging can be accomplished only if one is aware of the normal distribution pattern, physiological variants of radiotracer uptake, and potential sources of false-positive and false-negative imaging findings. In recent years, a growing number of reports have come to light describing incidental non-prostatic benign or malignant pathologies with high uptake on PSMA-targeted PET imaging. In this review, we have summarized the published literature regarding the potential pearls and technical and interpretive pitfalls of this imaging modality. Knowledge of these limitations can increase the confidence of interpreting physicians and thus improve patient care.

CONCLUSIONS

As PSMA-targeted PET is expected to be evaluated in larger prospective trials, the dissemination of potential diagnostic pitfalls and the biologic underpinning of those findings will be of increased importance.

PSMA Ligands for PET Imaging of Prostate Cancer

Targeting the prostate-specific membrane antigen (PSMA) with ⁶⁸Ga-labeled and ¹⁸F-labeled PET agents has become increasingly important in recent years. Imaging of biochemically recurrent prostate cancer has been established as a widely accepted clinical indication for PSMA ligand PET/CT in many parts of the world because of the results of multiple, primarily retrospective, studies that indicate superior detection efficacy compared with standard-of-care imaging. For high-risk primary prostate cancer, evidence is growing that this modality significantly aids in the detection of otherwise occult nodal and bone metastases. For both clinical indications in recurrent as well as in primary prostate cancer, preliminary data demonstrate a substantial impact on clinical management. Emerging data imply that intraprostatic tumor localization, therapy stratification, and treatment monitoring of advanced disease in specific clinical situations might become future indications. Current criteria for image reporting of PSMA ligand PET are evolving given the expanding body of literature on physiologic and pathologic uptake patterns and pitfalls. This article intends to give an educational overview on the current status of PSMA ligand PET imaging, including imaging procedure and interpretation, clinical indications, diagnostic potential, and impact on treatment planning.

Diagnostic performance of 68Ga-PSMA-11 (HBED-CC) PET/CT in patients with recurrent prostate cancer: evaluation in 1007 patients

Purpose

Since the clinical introduction of ⁶⁸Ga-PSMA-11 PET/CT, this imaging method has rapidly spread and is now regarded as a significant step forward in the diagnosis of recurrent prostate cancer (PCa). The aim of this study was to analyse the influence of several variables with possible influence on PSMA ligand uptake in a large cohort.

Methods

We performed a retrospective analysis of 1007 consecutive patients who were scanned with ⁶⁸Ga-PSMA-11 PET/CT (1 h after injection) from January 2014 to January 2017 to detect recurrent disease. Patients with untreated primary PCa or patients referred for PSMA radioligand therapy were excluded. The possible effects of different variables including PSA level and PSA doubling time (PSA_DT), PSA velocity (PSA_Vel), Gleason score (GSC, including separate analysis of GSC 7a and 7b), ongoing androgen deprivation therapy (ADT), patient age and amount of injected activity were evaluated.

Results

In 79.5% of patients at least one lesion with characteristics suggestive of recurrent PCa was detected. A pathological (positive) PET/CT scan was associated with PSA level and ADT. GSC, amount of injected activity, patient age, PSA_DT and PSA_Vel were not associated with a positive PET/CT scan in multivariate analysis.

Conclusion

⁶⁸Ga-PSMA-11 PET/CT detects tumour lesions in a high percentage of patients with recurrent PCa. Tumour detection is clearly associated with PSA level and ADT. Only a tendency for an association without statistical significance was found between higher GSC and a higher probability of a pathological PET/CT scan. No associations were found between a pathological ⁶⁸Ga-PSMA-11 PET/CT scan and patient age, amount of injected activity, PSA_DT or PSA_Vel.

Electronic supplementary material

The online version of this article (doi:10.1007/s00259-017-3711-7) contains supplementary material, which is available to authorized users.