Intra-Individual Comparison of 18F-PSMA-1007 and 18F-FDG PET/CT in the Evaluation of Patients With Prostate Cancer

Description of FDG and Prostate-Specific Membrane Antigen PET/CT Findings in Korean Patients With Advanced Metastatic Castration-Resistant Prostate Cancer

OBJECTIVE

We aimed to describe the [18F]fluorodeoxyglucose (FDG) and prostate-specific membrane antigen (PSMA) PET/CT findings in Korean men with advanced metastatic castration-resistant prostate cancer (mCRPC).

MATERIALS AND METHODS

The results of paired FDG and PSMA PET/CT examinations performed in 42 consecutive men with prostate cancer for treatment planning after failure of anti-androgen therapy and chemotherapy were studied. Tumor lesions with FDG or PSMA uptake intensity higher than that of the liver on visual review were considered positive and noted per patient and tumor site (prostate bed, lymph node, bone, and visceral organ). The presence of unequivocally discordant FDG and PSMA uptake patterns in tumor lesions was assessed. Patients were grouped according to the total tumor volume as seen on each PET/CT scan, and the clinical findings between the patient groups were compared using the Mann-Whitney U test.

RESULTS

On patient-based analysis, the image findings were PSMA+/FDG- in 2 patients, PSMA-/FDG+ in one, and PSMA+/FDG+ in 39 patients. On site-based analysis, the discordance (PSMA+/FDG- or PSMA-/FDG+) rate was 9.5% (4/42) for prostate/bed, 11.9% (5/42) for lymph nodes, 9.5% (4/42) for bones, and 11.9% (5/42) for visceral organs. FDG uptake was higher than PSMA uptake in at least one tumor site in 54.8% (23/42) of patients. Patients with greater total tumor volume on FDG PET/CT than that on PSMA PET/CT ("FDG-dominant pattern") accounted for 28.6% (12/42), and they had significantly shorter time from diagnosis (median 25 months vs. 62 months, P = 0.049), and higher aspartate aminotransferase (median 28.5 vs. 22.5, P = 0.027) and lactate dehydrogenase (median 341.5 vs. 224.5, P = 0.010) levels.

CONCLUSION

Most patients with advanced mCRPC had tumors with positive findings on both FDG and PSMA PET/CT. However, the uptake patterns varied; 54.8% of the patients had tumor(s) with FDG uptake greater than PSMA uptake, and FDG-dominant pattern was noted in 28.6% of the patients.

PET radiotracers for whole-body in vivo molecular imaging of prostatic neuroendocrine malignancies

Prostatic neuroendocrine malignancies represent a spectrum of diseases. Treatment-induced neuroendocrine differentiation (tiNED) in hormonally treated adenocarcinoma has been the subject of a large amount of recent research. However, the identification of neuroendocrine features in treatment-naïve prostatic tumor raises a differential diagnosis between prostatic adenocarcinoma with de novo neuroendocrine differentiation (dNED) versus one of the primary prostatic neuroendocrine tumors (P-NETs) and carcinomas (P-NECs). While [18F]FDG is being used as the main PET radiotracer in oncologic imaging and reflects cellular glucose metabolism, other molecules labeled with positron-emitting isotopes, mainly somatostatin-analogues labeled with 68Ga and prostate-specific membrane antigen (PSMA)-ligands labeled with either 18F or 68Ga, are now routinely used in departments of nuclear medicine and molecular imaging, and may be advantageous in imaging prostatic neuroendocrine malignancies. Still, the selection of the preferred PET radiotracer in such cases might be challenging. In the current review, we summarize and discuss published data on these different entities from clinical, biological, and molecular imaging standpoints. Specifically, we review the roles that [18F]FDG, radiolabeled somatostatin-analogues, and radiolabeled PSMA-ligands play in these entities in order to provide the reader with practical recommendations regarding the preferred PET radiotracers for imaging each entity. In cases of tiNED, we conclude that PSMA expression may be low and that [18F]FDG or radiolabeled somatostatin-analogues should be preferred for imaging. In cases of prostatic adenocarcinoma with dNED, we present data that support the superiority of radiolabeled PSMA-ligands. In cases of primary neuroendocrine malignancies, the use of [18F]FDG for imaging high-grade P-NECs and radiolabeled somatostatin-analogues for imaging well-differentiated P-NETs is recommended. KEY POINTS: • The preferred PET radiotracer for imaging prostatic neuroendocrine malignancies depends on the specific clinical scenario and pathologic data. • When neuroendocrine features result from hormonal therapy for prostate cancer, PET-CT should be performed with [18F]FDG or radiolabeled somatostatin-analogue rather than with radiolabeled PSMA-ligand. • When neuroendocrine features are evident in newly diagnosed prostate cancer, differentiating adenocarcinoma from primary neuroendocrine malignancy is challenging but crucial for selection of PET radiotracer and for clinical management.

An exploratory study of unexplained concentration of 18F-PSMA-1007 in the bladder for prostate cancer PET/CT imaging

18F-PSMA-1007 PET/CT imaging is increasingly used for the diagnosis, staging, and efficacy assessment of patients with prostate cancer. Compared with other PSMA tracers, 18F-PSMA-1007 is mainly cleared by the liver and bile and has lower urinary clearance, thus allowing a better assessment of the lesions around the bladder. However, there were some patients who showed an obvious concentration of the 18F-PSMA-1007 in the bladder, which may affect the observation of peripheral lesions, but the mechanism of this change is unknown. The aim of this study was to explore the cause of bladder 18F-PSMA-1007 concentration by assessing the clinical and imaging characteristics of 18F-PSMA-1007 PET/CT scans. A total of 284 patients were included in this retrospective study, and their clinical characteristics such as age, height, weight, Gleason score, metastases, different treatment methods, the level of liver and kidney function, PSA level, and imaging characteristics such as 18F-PSMA-1007 injected activity, the interval between injection to scan, physiological distribution (parotid gland, kidney, liver, spleen, intestine, obturator internus), pathological distribution (prostate lesions, metastases) were collected, and were compared after subgrouping using bladder urine SUVmax. This study showed that the distribution of bladder 18F-PSMA-1007 was not correlated with the above clinical and imaging characteristics, so further studies are needed to find the explanations, and thus to improve the disease assessment of this type of prostate cancer patients.

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

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSION

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

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

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

FOMSy: 3D-printed flexible open-source microfluidic system and flow synthesis of PET-tracer

In this work, we introduce a low-cost open-source flow system that includes a dual syringe pump with implemented pressure sensor and back pressure regulator. The entire system can be built for around 500 €. Commercially available flow systems can be very expensive with equipment starting at, but often greatly exceeding, 10,000 €. This high price of entry makes such technology prohibitively expensive for many research groups. Such systems stand to benefit the emerging academic pharmaceutical field by providing the experience and availability of reliable and affordable solutions. To implement accessible flow chemistry at research facilities, the systems must be made affordable. In addition, space in research laboratories is usually limited and commercially available flow systems can be very bulky. Having a compact and individually adjustable system is thus beneficial, with 3D printing technology offering the solution. Our compact 3D-printed system meets the needs of many applications in flow chemistry research as well as educational requirements for universities. As a proof of concept, we conceptualized, developed, and tested a custom flow system that can be used to synthesize [18F]2-fluoro-2-desoxy-d-glucose ([18F]FDG), the most commonly used PET-tracer. This system was designed to perform the typical functions and operations required in radiotracer production i.e. radiofluorination, dilution, SPE-trapping, deprotection, and SPE-elution. With this proof-of-concept in hand, the system can be easily customized to produce other radiopharmaceuticals.

Clinical advancement of precision theranostics in prostate cancer

Theranostic approaches with positron emission tomography/computed tomography (PET/CT) or PET/magnetic resonance imaging (PET/MRI) molecular imaging probes are being implemented clinically in prostate cancer (PCa) diagnosis and imaging-guided precision surgery. This review article provides a comprehensive summary of the rapidly expanding list of molecular imaging probes in this field, including their applications in early diagnosis of primary prostate lesions; detection of lymph node, skeletal and visceral metastases in biochemical relapsed patients; and intraoperative guidance for tumor margin detection and nerve preservation. Although each imaging probe shows preferred efficacy in some applications and limitations in others, the exploration and research efforts in this field will eventually lead to improved precision theranostics of PCa.

Dual-Tracer PET-Computed Tomography Imaging for Precision Radio-Molecular Theranostics of Prostate Cancer: A Futuristic Perspective

Dual/multi-tracer PET-computed tomography (CT) scan has been an interesting and intriguing concept and is promising in noninvasive and overall characterization of tumor biology and heterogeneity and has scientifically augmented the practice of precision oncology. In prostate carcinoma, particularly in metastatic castration-resistant prostate carcinoma setting, dual-tracer PET-CT can be potentially useful in selecting patients for chemotherapy, androgen deprivation therapy or prostate-specific membrane antigen (PSMA)-based peptide receptor radioligand therapy either as mono-therapy or as combination therapy, ascertaining differentiation status, staging/restaging, prognostication, and predicting progression/response. PSMA PET/CT has great potential as a "rule out" test in baseline staging, while being very useful in restaging and metastatic workup.

The Detection Performance of 18 F-Prostate-Specific Membrane Antigen-1007 PET/CT in Primary Prostate Cancer : A Systemic Review and Meta-analysis

BACKGROUND

Multiple tools are now available to determine the requirement for a biopsy to diagnose prostate cancer, and PET/CT with radiolabeled prostate-specific membrane antigen (PSMA)-targeting radiotracers has been recommended for detecting primary prostate cancer. Particularly, the radiotracer 18 F-PSMA-1007 was found to be more favorable for primary tumors compared with other PSMA-targeting radiotracers because of its low clearance via the urinary tract and better image resolution. Thus, we performed a systematic review and meta-analysis to more accurately evaluate the detection performance of 18 F-PSMA-1007 PET/CT in primary prostate cancer patients.

METHODS

An update on the databases of PubMed/MEDLINE, EMBASE, and Cochrane Library for comprehensive literature search was performed on September 30, 2021. The pooling detection rate was calculated on a per-patient basis. The pooling median of the SUV max was analyzed from the included studies. Furthermore, the positive predictive value of 18 F-PSMA-1007 PET/CT with pathologic lesions was analyzed using the criterion standard.

RESULTS

Twelve studies (540 patients total) were included in the meta-analysis. The overall pooling detection rate of 18 F-PSMA-1007 per patient was 94%, and the pooling median of SUV max located at the intraprostate tumor was 16 (range, 3.7-77.7). The positive predictive value of 18 F-PSMA-1007 per lesion with histopathological validation was 0.90, detecting regional lymph node metastasis was 0.94, and detecting localized prostatic tumors was 0.84.

CONCLUSIONS

In the current meta-analysis, we revealed the excellent performance of 18 F-PSMA-1007 to detect localized prostatic tumor lesions and regional lymph node metastasis. Moreover, the uptake of localized tumors in primary prostate cancer was nearly liver uptake and may be considered a suspicious malignancy if it was equal to or greater than the liver uptake.

Potential Pitfall in the Interpretation of Ganglioneuronal Uptake of 18 F-PSMA-1007 PET/CT Scans Performed With a High Spatial Resolution Digital PET Scanner

ABSTRACT

A 69-year-old man with biochemical recurrence of prostate cancer after radical prostatectomy 5 years previously and subsequent salvage radiotherapy to the prostate bed and pelvic nodes underwent PET/CT on a Siemens mCT Flow PET and a second PET/CT 10 months later on a Siemens Vision 600 Digital PET. In addition to a suspicious left hilar lymph node, the new high-resolution PET showed increased visualization and avidity of physiologic uptake in paraspinal and presacral sympathetic ganglia. Caution should be undertaken when interpreting PET/CTs performed on high-resolution digital scanners to avoid mistaking ganglia uptake for metastatic disease.

Primary Staging of Prostate Cancer Patients with [18F]PSMA-1007 PET/CT Compared with [68Ga]Ga-PSMA-11 PET/CT

Background: Hybrid imaging with prostate-specific membrane antigen (PSMA) is gaining importance as an increasingly meaningful tool for prostate cancer (PC) diagnostics and as a guide for therapy decisions. This study aims to investigate and compare the performance of [¹⁸F]PSMA-1007 (¹⁸F-PSMA) and [⁶⁸Ga]Ga-PSMA-11 positron emission tomography/computed tomography (⁶⁸Ga-PSMA) in the initial staging of PC patients. Methods: The data of 88 biopsy-proven patients were retrospectively evaluated. PSMA-avid lesions were compared with the histopathologic Gleason Score (GS) for prostate biopsies, and the results were plotted by receiver operating characteristic (ROC)-curve. Optimal maximum standardized uptake value (SUV_max) cut-off values were rated using the Youden index. Results: ¹⁸F-PSMA was able to distinguish GS ≤ 7a from ≥7b with a sensitivity of 62%, specificity of 85%, positive predictive value (PPV) of 92%, and accuracy of 67% for a SUV_max of 8.95, whereas sensitivity was 54%, specificity 91%, PPV 93%, and accuracy 66% for ⁶⁸Ga-PSMA (SUV_max 8.7). Conclusions: Both methods demonstrated a high concordance of detected PSMA-avid lesions with histopathologically proven PC. ¹⁸F-PSMA and ⁶⁸Ga-PSMA are both suitable for the characterization of primary PC with a comparable correlation of PSMA-avid lesions with GS. Neither method showed a superior advantage. Our calculated SUV_max thresholds may represent valuable parameters in clinical use to distinguish clinically significant PC (csPC) from non-csPC.

Detection rate of fluorine-18 prostate-specific membrane antigen-1007 PET/CT for prostate cancer in primary staging and biochemical recurrence with different serum PSA levels: A systematic review and meta-analysis

Background

We performed a systematic review and meta-analysis to evaluate the detection rate (DR) of fluoro-prostate-specific membrane antigen (¹⁸F-PSMA-1007) PET/CT in patients with different serum prostate-specific antigen (PSA) levels in the setting of primary staging of prostate cancer (PCa) or biochemically recurring PCa.

Methods

A comprehensive electronic literature search of the PubMed, Embase, and Cochrane Library databases was conducted in accordance with the PRISMA statement. This study was registered in the PROSPERO database (registration number: CRD42022331595). We calculated the DR of ¹⁸F-PSMA-1007 PET/CT in PCa.

Results

The final analysis included 15 studies that described 1,022 patients and 2,034 lesions with ¹⁸F-PSMA-1007 PET/CT in PCa. The DR of ¹⁸F-PSMA-1007 PET/CT in patients with PCa in primary staging ranged from 90% to 100%, with a pooled estimate of 94% (95% CI: 92%–96%). The DR of ¹⁸F-PSMA-1007 PET/CT in patients with PCa in BCR ranged from 47% to 100%, with a pooled estimate of 86% (95% CI: 76%–95%). The DRs of PSA levels >2.0, 1.1–2.0, 0.51–1.0, and ≤0.5 ng/ml detected by ¹⁸F-PSMA-1007 PET/CT in a patient-based analysis were 97% (95% CI: 93%–99%), 95% (95% CI: 88%–99%), 79% (95% CI: 68%–88%), and 68% (95% CI: 58%–78%), respectively.

Conclusion

This meta-analysis concluded that ¹⁸F-PSMA-1007 PET/CT had a high application value for prostate cancer, including primary tumors and biochemical recurrence. The DR of ¹⁸F-PSMA-1007 PET/CT was slightly higher in primary prostate tumors than in biochemical recurrence.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022331595.

Physiological tracer distribution and benign lesion incidental uptake of Al18F-NOTA-FAPI-04 on PET/CT imaging

OBJECTIVE

To systematically investigate the physiological distribution and benign lesion incidental uptake of Al18F-NOTA-FAPI-04 (18F-FAPI) in cancer patients to establish the normal uptake range in relevant organs and lesions.

METHODS

Twenty patients who underwent 18F-FAPI PET/CT imaging were retrospectively assessed. Organ and benign lesion tracer uptake was quantified based on standardized uptake values (SUVmax and SUVmean). We compared the variation in tracer uptake in certain organs between men and women, analyzed the possible reasons for diffuse uptake in the thyroid, and assessed tracer uptake variations in the uterus in different menstrual cycle phases. Incidental tracer uptake in benign lesions was also assessed.

RESULTS

Physiological 18F-FAPI uptake was observed in the urinary tract, biliary tract system, submandibular glands, pancreas, thyroid, uterus, intestine, prostate gland, parotid gland, myocardium, kidney cortex, and muscles, but not the brain, lungs, liver, spleen, colon, and breasts. The SUVmean for each organ was similar for women and men (all P > 0.05). Diffuse tracer uptake in the thyroid was caused by normal thyroid or thyroiditis; there were no statistically significant differences between them (SUVmax: t = -1.3, P = 0.25; SUVmean: t = -1.1, P = 0.31). There was a significant difference for uterus uptake among different menstrual cycle phases (SUVmax: F = 5.08, P = 0.04; SUVmean: F = 5.19, P = 0.04). Incidental benign lesion tracer uptake was observed in patients with esophagitis, thyroiditis, arthritis, fractures, and uterine fibroids.

CONCLUSION

This study provides a reference range for 18F-FAPI uptake in relevant organs and benign lesions. Benign lesion 18F-FAPI uptake may reduce 18F-FAPI PET/CT specificity.

An Explorative Study of the Incidental High Renal Excretion of [18F]PSMA-1007 for Prostate Cancer PET/CT Imaging

Positron emission tomography (PET) of prostate-specific membrane antigen (PSMA) allows for accurate diagnosis and staging of prostate cancer (PCa). Compared to other PSMA PET tracers available, [18F]PSMA-1007 is predominantly excreted via the hepatobiliary tract resulting in low renal excretion which improves evaluation of the pelvic area. However, some patients do show high urinary uptake of [18F]PSMA-1007. The present study aimed to investigate this sudden high urinary uptake of [18F]PSMA-1007 by evaluating [18F]PSMA-1007 PET scans from PCa patients. In this single-center retrospective study, patients that underwent [18F]PSMA-1007 PET imaging between July 2018 and January 2021 were included. Data regarding the individual patient characteristics, scan acquisition and batch production were analyzed. To determine the urinary excretion of [18F]PSMA-1007, a region of interest was drawn in the bladder, and standardized uptake values (SUVs) were calculated and compared to SUVs in the prostate. An SUVmax of >10 was considered high urinary excretion, an SUVmax 7.5−10 intermediate and an SUVmax < 7.5 low urinary excretion. A total of 344 patients underwent [18F]PSMA-1007 PET/CT imaging, with 37 patients receiving three or more [18F]PSMA-1007 PET/CT scans. The mean SUVmean and SUVmax of the bladder were 3.9 (SD 2.9) and 5.9 (SD 4.2), respectively. Fourteen percent of patients showed high urinary uptake of [18F]PSMA-1007. Twelve of the thirty-seven patients (32.4%) that had multiple scans showed a varying urinary uptake of [18F]PSMA-1007 per PSMA PET/CT scan. In terms of patient characteristics, risk factors, medication and blood laboratory results, no significant influencing variables were found. Nor was there a difference observed in the batch size and the mean radiochemical purity of PSMA-1007 for high- and low-excreting patients. However, the bladder volume affected the mean SUVmax in the bladder significantly, with higher SUVs in lower bladder volumes. In this study, we observed that a higher SUV in the urinary tract seemed to occur in patients with low bladder volume. A prospective study is needed to corroborate this hypothesis.

Evaluation of 18F-PSMA-1007 PET/CT in prostate cancer patients with biochemical recurrence after radical prostatectomy

PURPOSE

Prostate-specific membrane antigen (PSMA) ligands targeting has shown promising results in staging of prostate cancer (PCa). The aim of present study was to evaluate the value of ¹⁸F-PSMA-1007 PET/CT in PCa patients with biochemical recurrence.

METHODS

71 patients with PCa after radical prostatectomy (RP) were included in the present study. Median prostate-specific antigen (PSA) level was 1.27 ng/mL (range 0.01-67.40 ng/mL, n = 69). All patients underwent whole-body PET/CT imaging after injection of 333±38 MBq ¹⁸F-PSMA-1007. The distribution of PSMA-positive lesions was assessed. The influence of PSA level, androgen deprivation therapy and primary Gleason score on PSMA-positive finding and uptake of ¹⁸F-PSMA-1007 were evaluated.

RESULTS

56 (79%) patients showed at least one pathological finding on ¹⁸F-PSMA-1007 PET/CT. The rates of positive scans were 50%, 80%, 100%, 100% among patients with PSA levels ≤0.5, 0.51-1.0, 1.1-2.0 and >2.0 ng/mL, respectively. The median Gleason score was 8 (range 7-10), and higher Gleason score (≤7 vs. ≥8) leads to higher detection rates (58.3% (14/24) vs. 88.9% (32/36), P = 0.006). The median SUVmax of positive findings in patients with PSA levels ≤0.5, 0.51-1.0, 1.1-2.0 and >2.0 ng/mL were 4.51, 4.27, 11.50 and 14.08, respectively. The median SUVmax in patients with PSA level >2.0 ng/mL was significantly higher than that in patients with PSA ≤2.0 ng/mL (14.08 vs. 6.13, P<0.001).

CONCLUSION

¹⁸F-PSMA-1007 PET/CT demonstrated a high detection rate for patients with a raised PSA level after radical prostatectomy even in patients with extremely low PSA level (eg. PSA level ≤0.5 ng/mL), which was essential for further clinical management for PCa patients.

Dual-Tracer Positron-Emission Tomography Using Prostate-Specific Membrane Antigen and Fluorodeoxyglucose for Staging of Prostate Cancer: A Systematic Review

PSMA PET is more accurate than conventional imaging (CT/bone scan) for staging of intermediate- or high-risk prostate cancer (PCa), but 5–10% of primary tumours have low PSMA ligand uptake. FDG PET has been used to further define disease extent in end-stage castrate-resistant PCa and may be beneficial earlier in the disease course for more accurate staging. The objective of this study was to review the available evidence for patients undergoing both FDG and PSMA PET for PCa staging at initial diagnosis and in recurrent disease. A systematic literature review was performed for studies with direct, intraindividual comparison of PSMA and FDG PET for staging of PCa. Assessment for radioligand therapy eligibility was not considered. Risk of bias was assessed. 543 citations were screened and assessed. 13 case reports, three retrospective studies, and one prospective study were included. FDG after PSMA PET improved the detection of metastases from 65% to 73% in high-risk early castration-resistant PCa with negative conventional imaging (M0). Positive FDG PET was found in 17% of men with negative PSMA PET for postprostatectomy biochemical recurrence. Gleason score ≥8 and higher PSA levels predicted FDG-avid metastases in BCR and primary staging. Variant histology (ductal and neuroendocrine) was common in case reports, resulting in PSMA-negative FDG-positive imaging for 3 patients. Dual-tracer PET for PCa may assist in characterising high-risk disease during primary staging and restaging. Further studies are required to determine the additive benefit of FDG PET and if the FDG-positive phenotype may indicate a poorer prognosis.

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.