F-Prostate-specific membrane antigen (PSMA)-1007 is mainly excreted through the liver. We benchmarked the performance of 18 F-PSMA-1007 against three renally excreted PSMA-tracers. Methods: Among 668 patients we selected 27 patients in whom the PET/CT with 68 Ga-PSMA-11, 18 F-DCFPyL, or 18 F-JK-PSMA-7 was interpreted as equivocal or negative or as oligometastatic disease (PET-1). Within <3 weeks, a second PET scan with 18 F-PSMA-1007 was performed (PET-2). The confidence in the interpretation of PSMA-positive loco-regional findings was scored on a 5-point scale, first in routine diagnostics (reader 1), then by an independent second evaluation (reader 2). Discordant PSMA-positive skeletal findings were examined by contrast enhanced MRI. Results: For both readers, 18 F-PSMA-1007 facilitated the interpretability of 27 loco-regional lesions. In PET-2, the clinical read-out led to a significantly lower number of equivocal loco-regional lesions (p=0.024), reader 2 reported a significantly higher rate of suspicious lesions that were falsely interpreted as probably benign in PET-1 (p=0.023). Exclusively on PET-2, we observed a total of 15 PSMA-positive PSMA-spots in the bone marrow of 6 patients (= 22%). None of the 15 discordant spots had a morphological correlate on the corresponding CT or on the subsequent MRI. Thus, 18 F-PSMA-1007 exhibits a significantly higher rate of unspecific medullary spots (p=0.0006). Conclusion: 18 F-PSMA-1007 may increase confidence to interpret small loco-regional lesions adjacent to the urinary tract. However, it may decrease the interpretability of skeletal lesions.
Aim We investigated the whole-body distribution and the radiation dosimetry of [ 18 F]-JK-PSMA-7, a novel 18 F-labeled PSMA-ligand for PET/CT imaging of prostate cancer. Methods Ten patients with prostate cancer and biochemical recurrence or radiologic evidence of metastatic diseases were examined with 329–384 MBq (mean 359 ± 17 MBq) [ 18 F]-JK-PSMA-7. Eight sequential positron emission tomography (PET) scans were acquired from 20 min to 3 h after injection with IRB approval. The kidneys, liver, lungs, spleen, and salivary glands were segmented into volumes of interest using the QDOSE dosimetry software suite (ABX-CRO, Germany). Absorbed and effective dose were calculated using the ICRP-endorsed IDAC 1.0 package. The absorbed dose of the salivary glands was determined using the spherical model of OLINDA 1.1. PSMA-positive lesions were evaluated separately. Quantitative assessment of the uptake in suspicious lesions was performed by analysis of maximum (max) and peak SUV values. The gluteus maximus muscle (SUV mean ) served as a reference region for the calculation of tumor-to-background ratios (TBR’s). Results Physiologic radiotracer accumulation was observed in the salivary and lacrimal glands, liver, spleen, and intestines, in a pattern resembling the distribution known from other PSMA-tracers with excretion via urinary and biliary pathways. The effective dose from [ 18 F]-JK-PSMA-7 for the whole body was calculated to be 1.09E−02 mGy/MBq. The highest radiation dose was observed in the kidneys (1.76E−01 mGy/MBq), followed by liver (7.61E−02 mGy/MBq), salivary glands (4.68E−02 mGy/MBq), spleen (1.89E−02 mGy/MBq), and lungs (1.10E-2 mGy/MBq). No adverse effects of tracer injection were observed. Six out of ten patients were scored as PSMA-positive. A total of 18 suspicious lesions were analyzed, which included six bone lesions, nine lymph nodes, and three local lesions within the prostate fossa. The values for the SUV max and SUV peak in the PSMA-positive lesions increased until 60 min p.i. and remained at this intensity in the PET/CT scans until 140 min. In the period between 170 and 200 min after injection, a further significant increase in SUV max and SUV peak within the PSMA-positive lesions was observed. Conclusions The highest TBR of [ 18 F]-JK-PSMA-7 was found 3 h after injection. From the kinetically collected data, it can be concluded that this trend may also continue in the further course. The start of the PET/CT acquisition should be chosen as late as possible. The high uptake in suspicious lesions in terms of absolute SUV max and relative TBR values indicates potentially high sensitivity of the tracer for d...
Prostate-specific membrane antigen (PSMA) PET/CT has a high diagnostic accuracy for lesion detection in metastatic prostate cancer, including bone metastases. Novel therapeutic approaches require valid biomarkers for standardized disease staging and for evaluation of progression and therapy response. Here, we introduce EBONI (Evaluation of Bone Involvement), a software tool to automatically quantify the bone metastasis load in PSMA PET/CT. Lesion quantity, mean and maximum lesional SUV, score, and percentage of affected bone volume are determined. EBONI is open source and freely available. To validate EBONI, the results of automated quantification of 38 PSMA PET/CT scans with different levels of bone involvement were compared with visual expert reading. The influence of SUV threshold and Hounsfield unit thresholds was analyzed. A high correlation between bone lesion quantity as determined visually and automatically was found (SUV, = 0.97; SUV, = 0.88; lesion count, = 0.97). The Hounsfield unit threshold had no significant influence, whereas an SUV threshold of 2.5 proved optimal for automated lesion quantification. The systematic error of false-positive tissue misclassification was low, occurred mainly around the salivary and lacrimal glands, and could easily be corrected. There were no false-negative ratings. EBONI analysis is robust, quick (<3 min per scan), and 100% reproducible. It allows rater-independent quantification of bone metastasis in metastatic prostate cancer. It provides lesion quantification equivalent to that of visual assessment, as well as providing complementary information. It can be easily implemented as an add-on to visual analysis of PSMA PET/CT scans and has the potential to reduce turnaround time.
The time period between injection and data acquisition influences the detection rate of [Ga]PSMA-HBED-CC PET/CT. In biochemical recurrence with low PSA levels, late [Ga]PSMA-HBED-CC PET/CT imaging offers frequent advantages with regard to lesion contrast.
In preclinical trials, the recently developed tracer 2-methoxy-18 F-DCFPyL ( 18 F-JK-prostate-specific membrane antigen [PSMA]-7) has shown favorable properties regarding clinical performance and radiochemical accessibility. The aim of this study was to evaluate the clinical utility of 18 F-JK-PSMA-7 for PET/CT imaging of patients with prostate cancer. Methods: In an Institutional Review Board-approved pilot study, the initial clinical utility of PET/CT imaging with 18 F-JK-PSMA-7 was directly compared with 68 Ga-PSMA-11 PET/CT in a group of 10 patients with prostate cancer. The 2 PSMA tracers were administered to each patient less than 3 wk apart. Next, we analyzed the data of 75 consecutive patients who had undergone clinical 18 F-JK-PSMA-7 PET/CT imaging for tumor localization of biochemical recurrence (BCR). Results: The pilot study in 10 patients who were examined with both PSMA tracers demonstrated that 18 F-JK-PSMA-7 was at least equivalent to 68 Ga-PSMA-11. All unequivocally 68 Ga-PSMA-11-positive lesions could be also detected using 18 F-JK-PSMA-7, and in 4 patients additional suspected PSMA-positive lesions were identified (1 patient changed from PSMA-negative to PSMA-positive). In patients with BCR (after prostatectomy or radiotherapy), the capacity of 18 F-JK-PSMA-7 PET/CT to detect at least one PSMA-positive lesion was 84.8%. The prostate-specific antigen (PSA)-stratified detection rate of 18 F-JK-PSMA-7 after prostatectomy varied among 54.5% (6/11 patients; PSA , 0.5 μg/L), 87.5% (14/16 patients; PSA 0.5-2 μg/L), and 90.9% (20/22 patients; PSA . 2 μg/L). Conclusion: The tracer 18 F-JK-PSMA-7 was found to be safe and clinically useful. We demonstrated that 18 F-JK-PSMA-7 was not inferior when directly compared with 68 Ga-PSMA-11 in a pilot study but indeed identified additional PSMA-avid suspected lesions in oligometastasized patients with BCR. In a subsequent analysis of a clinical cohort of BCR patients, 18 F-JK-PSMA-7 was useful in tumor localization. 18 F-JK-PSMA-7 is recommended for future prospective trials.
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