Search

Detection of positive resection margins in surgical procedures of high-risk prostate cancer is key for minimizing the risk of recurrence. This study aimed at evaluating the accuracy of functional tumor-volume segmentation in intraoperative ex vivo PET/CT for margin assessment in prostate cancer patients undergoing radical prostatectomy. Methods: Seven high-risk prostate cancer patients received [ 18 F]PSMA-1007 before radical prostatectomy. After removal of the prostate gland, ex vivo imaging on the AURA 10 PET/CT system was performed, and functional tumor volume was segmented using 4 semiautomatic segmentation methods. Resection margins and volumes were compared with histopathology. Additionally, a supportive phantom study was conducted to assess segmentation accuracy at low radiopharmaceutical activity. Results: Clinically, 18 lesions were analyzed in intraoperative PET/CT. Sensitivity, specificity, and positive and negative predictive values of margin detection were 83%, 100%, 100%, and 92%, respectively, using an iterative thresholding method. In 1 patient, a biochemical recurrence was observed within 1 y of prostate-specific antigen follow-up, and 1 patient underwent adjuvant radiotherapy. The remaining 5 patients were still undergoing prostate-specific antigen follow-up with no evidence of biochemical recurrence. On the basis of a phantom-deduced minimal segmentable activity concentration of approximately 2 kBq/mL, we propose an administered [ 18 F]PSMA-1007 activity of at least 1.9 and 0.4 MBq/kg for preoperative and intraoperative injections, respectively. Conclusion: Intraoperative ex vivo PET/CT is a promising modality for intraoperative margin assessment. Prospective trials are needed to further investigate the value of specimen PET/CT-based radioguided surgery in high-risk prostate cancer., (© 2025 by the Society of Nuclear Medicine and Molecular Imaging.)

To assess the diagnostic accuracy of 68 Ga-labeled fibroblast activation protein inhibitor (FAPI) and 18 F-labeled FDG PET for the detection of various tumors, we performed a head-to-head comparison of both imaging modalities across a range of tumor entities as part of our ongoing 68 Ga-FAPI PET observational trial. Methods: The study included 115 patients with 8 tumor entities who received imaging with 68 Ga-FAPI for tumor staging or restaging between October 2018 and March 2022. Of those, 103 patients received concomitant imaging with 68 Ga-FAPI and 18 F-FDG PET and had adequate lesion validation for accuracy analysis. Each scan was evaluated for the detection of primary tumor, lymph nodes, and visceral and bone metastases. True or false positivity and negativity to detected lesions was assigned on the basis of histopathology from biopsies or surgical excision, as well as imaging validation. Results: 68 Ga-FAPI PET revealed higher accuracy than 18 F-FDG PET in the detection of colorectal cancer ( n = 14; per-patient, 85.7% vs. 78.6%; per-region, 95.6% vs. 91.1%) and prostate cancer ( n = 22; per-patient, 100% vs. 90.9%; per-region, 96.4% vs. 92.7%). 68 Ga-FAPI PET and 18 F-FDG PET had comparable per-patient accuracy in detecting breast cancer ( n = 16, 100% for both) and head and neck cancers ( n = 10, 90% for both modalities). 68 Ga-FAPI PET had lower per-patient accuracy than 18 F-FDG PET in cancers of the bladder ( n = 12, 75% vs. 100%) and kidney ( n = 10, 80% vs. 90%), as well as lymphoma ( n = 9, 88.9% vs. 100%) and myeloma ( n = 10, 80% vs. 90%). Conclusion: 68 Ga-FAPI PET demonstrated higher diagnostic accuracy than 18 F-FDG PET in the diagnosis of colorectal cancer and prostate cancer, as well as comparable diagnostic performance for cancers of the breast and head and neck. Accuracy and impact on management will be further assessed in an ongoing prospective interventional trial (NCT05160051)., (© 2024 by the Society of Nuclear Medicine and Molecular Imaging.)

We present an overview of our prospective fibroblast-activation protein inhibitor (FAPI) registry study across a 3-y period, with head-to-head comparison of tumor uptake in 68 Ga-FAPI and 18 F-FDG PET, as well as FAP immunohistochemistry. Methods: This is an interim analysis of the ongoing 68 Ga-FAPI PET prospective observational trial at our department. Patients who underwent clinical imaging with 68 Ga-FAPI PET between October 2018 and October 2021 were included. Tracer uptake was quantified by SUV max for tumor lesions and by SUV mean for normal organs. PET tumor volume (40% isocontour) and tumor-to-background ratios were calculated. Correlation between SUV max and FAP staining in tissue samples was analyzed. Results: In total, 324 patients with 21 different tumor entities underwent 68 Ga-FAPI imaging; 237 patients additionally received 18 F-FDG PET. The most common tumor entities were sarcoma (131/324, 40%), pancreatic cancer (67/324, 21%), and primary tumors of the brain (22/324, 7%). The mean primary tumor SUV max was significantly higher for 68 Ga-FAPI than 18 F-FDG among pancreatic cancer (13.2 vs. 6.1, P < 0.001) and sarcoma (14.3 vs. 9.4, P < 0.001), and the same was true for mean SUV max in metastatic lesions of pancreatic cancer (9.4 vs. 5.5, P < 0.001). Mean primary tumor maximum tumor-to-background ratio was significantly higher for 68 Ga-FAPI than 18 F-FDG across several tumor entities, most prominently pancreatic cancer (14.7 vs. 3.0, P < 0.001) and sarcoma (17.3 vs. 4.7, P < 0.001). Compared with 18 F-FDG, 68 Ga-FAPI showed superior detection for locoregional disease in sarcoma (52 vs. 48 total regions detected) and for distant metastatic disease in both sarcoma (137 vs. 131) and pancreatic cancer (65 vs. 57), respectively. Among 61 histopathology samples, there was a positive correlation between 68 Ga-FAPI SUV max and overall FAP immunohistochemistry score ( r = 0.352, P = 0.005). Conclusion: 68 Ga-FAPI demonstrates higher absolute uptake in pancreatic cancer and sarcoma, as well as higher tumor-to-background uptake along with improved tumor detection for pancreatic cancer, sarcoma, and other tumor entities when compared with 18 F-FDG. 68 Ga-FAPI is a new tool for tumor staging with theranostic potential., (© 2023 by the Society of Nuclear Medicine and Molecular Imaging.)

Intraoperative identification of positive resection margins (PRMs) in high-risk prostate cancer (PC) needs improvement. Cerenkov luminescence imaging (CLI) with 68 Ga-PSMA-11 is promising, although limited by low residual activity and artificial signals. Here, we aimed to assess the value of CLI and flexible autoradiography (FAR) with 18 F-PSMA-1007. Methods: Mice bearing subcutaneous PSMA-avid RM1-PGLS tumors were administered 18 F-PSMA-1007, and PET/CT was performed. After the animals had been killed, organs were excised and measured signals in CLI and FAR CLI were correlated with tracer activity concentrations (ACs) obtained from PET/CT. For clinical assessment, 7 high-risk PC patients underwent radical prostatectomy immediately after preoperative 18 F-PSMA PET/CT. Contrast-to-noise ratios (CNRs) were calculated for both imaging modalities in intact specimens and after incision above the index lesion. Results: In the heterotopic in vivo mouse model ( n = 5), CLI did not detect any lesion. FAR CLI detected a distinct signal in all mice, with a lowest AC of 7.25 kBq/mL (CNR, 5.48). After incision above the index lesion of the prostate specimen, no increased signal was observed at the cancer area in CLI. In contrast, using FAR CLI, a signal was detectable in 6 of 7 patients. The AC in the missed index lesion was 1.85 kBq/mL, resulting in a detection limit of at least 2.06 kBq/mL. Histopathology demonstrated 2 PRMs, neither of which was predicted by CLI or FAR CLI. Conclusion: 18 F-PSMA FAR CLI was superior to CLI in tracer-related signal detectability. PC was could be visualized in radical prostatectomy down to 2.06 kBq/mL. However, the detection of PRMs was limited. Direct anatomic correlation of FAR CLI is challenging because of the scintillator overlay., (© 2023 by the Society of Nuclear Medicine and Molecular Imaging.)

Cerenkov luminescence imaging (CLI) was successfully implemented in the intraoperative context as a form of radioguided cancer surgery, showing promise in the detection of surgical margins during robot-assisted radical prostatectomy. The present study was designed to provide a quantitative description of the occupational radiation exposure of surgery and histopathology personnel from CLI-guided robot-assisted radical prostatectomy after the injection of 68 Ga-PSMA-11 in a single-injection PET/CT CLI protocol. Methods: Ten patients with preoperative 68 Ga-PSMA-11 administration and intraoperative CLI were included. Patient dose rate was measured before PET/CT ( n  = 10) and after PET/CT ( n  = 5) at a 1-m distance for 4 patient regions (head [A], right side [B], left side [C], and feet [D]). Electronic personal dosimetry (EPD) was used for intraoperative occupational exposure ( n  = 10). Measurements included the first surgical assistant and scrub nurse at the operating table and the CLI imager/surgeon at the robotic console and encompassed the whole duration of surgery and CLI image acquisition. An estimation of the exposure of histopathology personnel was performed by measuring prostate specimens ( n  = 8) with a germanium detector. Results: The measured dose rate value before PET/CT was 5.3 ± 0.9 (average ± SD) μSv/h. This value corresponds to a patient-specific dose rate constant for positions B and C of 0.047 μSv/h⋅MBq. The average dose rate value after PET/CT was 1.04 ± 1.00 μSv/h. The patient-specific dose rate constant values corresponding to regions A to D were 0.011, 0.026, 0.024, and 0.003 μSv/h⋅MBq, respectively. EPD readings revealed average personal equivalent doses of 9.0 ± 7.1, 3.3 ± 3.9, and 0.7 ± 0.7 μSv for the first surgical assistant, scrub nurse, and CLI imager/surgeon, respectively. The median germanium detector-measured activity of the prostate specimen was 2.96 kBq (interquartile range, 2.23-7.65 kBq). Conclusion: Single-injection 68 Ga-PSMA-11 PET/CT CLI procedures are associated with a reasonable occupational exposure level, if kept under 110 procedures per year. Excised prostate specimen radionuclide content was below the exemption level for 68 Ga. Dose rate-based calculations provide a robust estimation for EPD measurements., (© 2022 by the Society of Nuclear Medicine and Molecular Imaging.)

Our objective was to assess the feasibility and accuracy of Cerenkov luminescence imaging (CLI) for assessment of surgical margins intraoperatively during radical prostatectomy. Methods: A single-center feasibility study included 10 patients with high-risk primary prostate cancer (PC). 68 Ga-prostate-specific membrane antigen (PSMA) PET/CT scans were performed followed by radical prostatectomy and intraoperative CLI of the excised prostate. In addition to imaging the intact prostate, in the first 2 patients the prostate gland was incised and imaged with CLI to visualize the primary tumor. We compared the tumor margin status on CLI to postoperative histopathology. Measured CLI intensities were determined as tumor-to-background ratio. Results: Tumor cells were successfully detected on the incised prostate CLI images as confirmed by histopathology. Three of 10 men had histopathologically positive surgical margins (PSMs), and 2 of 3 PSMs were accurately detected on CLI. Overall, 25 (72%) of 35 regions of interest proved to visualize a tumor signal according to standard histopathology. The median tumor radiance in these areas was 11,301 photons/s/cm 2 /sr (range, 3,328-25,428 photons/s/cm 2 /sr), and median tumor-to-background ratio was 4.2 (range, 2.1-11.6). False-positive signals were seen mainly at the prostate base, with PC cells overlaid by benign tissue. PSMA immunohistochemistry revealed strong PSMA staining of benign gland tissue, which impacts measured activities. Conclusion: This feasibility showed that 68 Ga-PSMA CLI is a new intraoperative imaging technique capable of imaging the entire specimen's surface to detect PC tissue at the resection margin. Further optimization of the CLI protocol, or the use of lower-energy imaging tracers such as 18 F-PSMA, is required to reduce false-positives. A larger study will be performed to assess diagnostic performance., (© 2020 by the Society of Nuclear Medicine and Molecular Imaging.)

Biochemical recurrence (BCR) is a concern for prostate cancer patients after local treatment. 68 Ga-labeled prostate-specific membrane antigen (PSMA) ligands have significantly improved prostate cancer imaging. However, several 18 F-labeled ligands that were developed as fluorinated tracers might present advantages. In this study, we analyzed the potential of 18 F-PSMA-1007 in patients with BCR. Methods: Twelve patients with BCR after local treatment underwent PET/CT scans 1 and 3 h after injection of 18 F-PSMA-1007. Results: 18 F-PSMA-1007 PET/CT detected lesions in 9 of 12 patients (75%). A significant difference was observed when comparing the tracer uptake in 18 F-PSMA-1007-positive lesions 1 and 3 h after injection (median SUV max , 7.00 vs. 11.34; P < 0.001; n = 76). Forty-four (88%) of 50 18 F-PSMA-1007-positive lymph nodes had a short-axis diameter of less than 8 mm. Conclusion: In this pilot study, 18 F-PSMA-1007 PET/CT presented high potential for localization of recurrent disease in prostate cancer patients with BCR., (© 2018 by the Society of Nuclear Medicine and Molecular Imaging.)

68 Ga-prostate-specific membrane antigen (PSMA) PET/CT is a promising diagnostic tool for patients with prostate cancer. Our study evaluates SUVs in benign prostate tissue and malignant, intraprostatic tumor lesions and correlates results with several clinical parameters. Methods: One hundred four men with newly diagnosed prostate carcinoma and no previous therapy were included in this study. SUV max was measured and correlated with biopsy findings and MRI. Afterward, data were compared with current prostate-specific antigen (PSA) values, Gleason score (GS), and d'Amico risk classification. Results: In this investigation a mean SUV max of 1.88 ± 0.44 in healthy prostate tissue compared with 10.77 ± 8.45 in malignant prostate lesions ( P < 0.001) was observed. Patients with higher PSA, higher GS, and higher d'Amico risk score had statistically significant higher PSMA uptake on PET/CT ( P < 0.001 each). Conclusion: PSMA PET/CT is well suited for detecting the intraprostatic malignant lesion in patients with newly diagnosed prostate cancer. Our findings indicate a significant correlation of PSMA uptake with PSA, GS, and risk classification according to the d'Amico scale., (© 2017 by the Society of Nuclear Medicine and Molecular Imaging.)

68 Ga-prostate-specific membrane antigen (PSMA)-11 PET/CT represents an advanced method for the staging of primary prostate cancer (PCa) and diagnosis of recurrent or metastatic PCa. However, because of the narrow availability of 68 Ga the development of alternative tracers is of high interest. The objective of this study was to examine the value of the new PET tracer 18 F-PSMA-1007 for the staging of local disease by comparing it with multiparametric MRI (mpMRI) and radical prostatectomy (RP) histopathology. Methods: In 2016, 18 F-PSMA-1007 PET/CT was performed in 10 men with biopsy-confirmed high-risk PCa. Nine patients underwent mpMRI in the process of primary diagnosis. Consecutively, RP was performed in all 10 men. Agreement analysis was performed retrospectively. PSMA staining was added for representative sections in RP specimen slices. Localization and agreement analysis of 18 F-PSMA-1007 PET/CT, mpMRI, and RP specimens was performed by dividing the prostate into 38 sections as described in the prostate imaging reporting and data system (PI-RADS) (version 2). Sensitivity, specificity, positive predictive values, negative predictive values (NPVs), and accuracy were calculated for total and near-total agreement. Results: 18 F-PSMA-1007 PET/CT had an NPV of 68% and an accuracy of 75%, and mpMRI had an NPV of 88% and an accuracy of 73% for total agreement. Near-total agreement analysis resulted in an NPV of 91% and an accuracy of 93% for 18 F-PSMA-1007 PET/CT and 91% and 87% for mpMRI, respectively. Retrospective combination of mpMRI and PET/CT had an accuracy of 81% for total and 93% for near-total agreement. Conclusion: Comparison with RP histopathology demonstrates that 18 F-PSMA-1007 PET/CT is promising for accurate local staging of PCa., (© 2017 by the Society of Nuclear Medicine and Molecular Imaging.)