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Rationale: The development of consensus guidelines for interpretation of Prostate-Specific Membrane Antigen (PSMA)-Positron Emission Tomography (PET) is needed to provide more consistent reports in clinical practice. The standardization of PSMA-PET interpretation may also contribute to increasing the data reproducibility within clinical trials. Finally, guidelines in PSMA-PET interpretation are needed to communicate the exact location of findings to referring physicians, to support clinician therapeutic management decisions. Methods: A panel of worldwide experts in PSMA-PET was established. Panelists were selected based on their expertise and publication record in the diagnosis or treatment of PCa, in their involvement in clinical guidelines and according to their expertise in the clinical application of radiolabeled PSMA inhibitors. Panelists were actively involved in all stages of a modified, nonanonymous, Delphi consensus process. Results: According to the findings obtained by modified Delphi consensus process, panelist recommendations were implemented in a structured report for PSMA-PET. Conclusions: The E-PSMA standardized reporting guidelines, a document supported by the European Association of Nuclear Medicine (EANM), provide consensus statements among a panel of experts in PSMA-PET imaging, to develop a structured report for PSMA-PET in prostate cancer and to harmonize diagnostic interpretation criteria. [ABSTRACT FROM AUTHOR]

Purpose: Quantitative prostate-specific membrane antigen (PSMA) PET analysis may provide for non-invasive and objective risk stratification of primary prostate cancer (PCa) patients. We determined the ability of machine learning-based analysis of quantitative [18F]DCFPyL PET metrics to predict metastatic disease or high-risk pathological tumor features. Methods: In a prospective cohort study, 76 patients with intermediate- to high-risk PCa scheduled for robot-assisted radical prostatectomy with extended pelvic lymph node dissection underwent pre-operative [18F]DCFPyL PET-CT. Primary tumors were delineated using 50–70% peak isocontour thresholds on images with and without partial-volume correction (PVC). Four hundred and eighty standardized radiomic features were extracted per tumor. Random forest models were trained to predict lymph node involvement (LNI), presence of any metastasis, Gleason score ≥ 8, and presence of extracapsular extension (ECE). For comparison, models were also trained using standard PET features (SUVs, volume, total PSMA uptake). Model performance was validated using 50 times repeated 5-fold cross-validation yielding the mean receiver-operator characteristic curve AUC. Results: The radiomics-based machine learning models predicted LNI (AUC 0.86 ± 0.15, p < 0.01), nodal or distant metastasis (AUC 0.86 ± 0.14, p < 0.01), Gleason score (0.81 ± 0.16, p < 0.01), and ECE (0.76 ± 0.12, p < 0.01). The highest AUCs reached using standard PET metrics were lower than those of radiomics-based models. For LNI and metastasis prediction, PVC and a higher delineation threshold improved model stability. Machine learning pre-processing methods had a minor impact on model performance. Conclusion: Machine learning-based analysis of quantitative [18F]DCFPyL PET metrics can predict LNI and high-risk pathological tumor features in primary PCa patients. These findings indicate that PSMA expression detected on PET is related to both primary tumor histopathology and metastatic tendency. Multicenter external validation is needed to determine the benefits of using radiomics versus standard PET metrics in clinical practice. [ABSTRACT FROM AUTHOR]

Purpose: Prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) is used for (re)staging prostate cancer (PCa) and as a biomarker for evaluating response to therapy, but lacks established response criteria. A panel of PCa experts in nuclear medicine, radiology, and/or urology met on February 21, 2020, in Amsterdam, The Netherlands, to formulate criteria for PSMA PET/CT-based response in patients treated for metastatic PCa and optimal timing to use it. Methods: Panelists received thematic topics and relevant literature prior to the meeting. Statements on how to interpret response and progression on therapy in PCa with PSMA PET/CT and when to use it were developed. Panelists voted anonymously on a nine-point scale, ranging from strongly disagree (1) to strongly agree (9). Median scores described agreement and consensus. Results: PSMA PET/CT consensus statements concerned utility, best timing for performing, criteria for evaluation of response, patients who could benefit, and handling of radiolabeled PSMA PET tracers. Consensus was reached on all statements. PSMA PET/CT can be used before and after any local and systemic treatment in patients with metastatic disease to evaluate response to treatment. Ideally, PSMA PET/CT imaging criteria should categorize patients as responders, patients with stable disease, partial response, and complete response, or as non-responders. Specific clinical scenarios such as oligometastatic or polymetastatic disease deserve special consideration. Conclusions: Adoption of PSMA PET/CT should be supported by indication for appropriate use and precise criteria for interpretation. PSMA PET/CT criteria should categorize patients as responders or non-responders. Specific clinical scenarios deserve special consideration. [ABSTRACT FROM AUTHOR]

Purpose: Radiolabeled Prostate-Specific Membrane Antigen (PSMA) PET/CT is the current standard-of-care for lesion detection in patients with biochemically recurrent (BCR) prostate cancer (PCa). However, rigorous verification of detected lesions is not always performed in routine clinical practice. To aid future 18F-radiolabeled PSMA PET/CT interpretation, we aimed to identify clinical/imaging characteristics that increase the likelihood that a PSMA-avid lesion is malignant. Materials and methods: 262 patients with BCR, who underwent 18F-DCFPyL PSMA PET/CT, were retrospectively analyzed. The malignant nature of 18F-DCFPyL PET-detected lesions was verified through any of the following metrics: (1) positive histopathological examination; (2) additional positive imaging; (3) a ≥50% decrease in Prostate-Specific Antigen (PSA) following irradiation of the lesion(s). Results: In 226/262 PET scans (86.3%) at least one lesion suspicious for recurrent PCa was detected ('positive scan'). In 84/226 positive scans (37.2%), at least one independent verification metric was available. PSMA PET-detected lesions were most often confirmed to be malignant (PCa) in the presence of a CT-substrate (96.5% vs. 55.6% without CT-substrate), with SUVpeak ≥3.5 (91.4% vs. 60.0% with SUVpeak<3.5), in patients with a PSA-level ≥2.0 ng/mL (83.7% vs. 65.7% in patients with PSA <2.0ng/mL) and in patients with >2 PET-positive lesions (94.1% vs. 64.2% in patients with 1–2 PET-positive lesions; p<0.001–0.03). Conclusions: In this study, the clinical verification of 18F-DCFPyL PET-positive lesions in patients with BCR was performed. Diagnostic certainty of PET-detected lesions increases in the presence of characteristic abnormalities on CT, when SUVpeak is ≥3.5, when PSA-levels exceed 2.0 ng/mL or in patients with more than two PET-positive lesions. [ABSTRACT FROM AUTHOR]

Many imaging-based clinical trials, however, merely incorporate research imaging as an additional component to routine imaging or utilise images acquired for clinical care. Contacting patients prior to the imaging visit, enquiring about possible symptoms, should reassure them that safety procedures are enforced and that imaging examinations can be re-scheduled where needed. Moreover, as imaging studies may potentially reveal incidental findings suggestive of pandemic-related (COVID-19) infection, information from structured and timely review of imaging findings communicated early to patients within trials would further incentivise them to attend imaging sessions. Organisational issues - institution and department policies Trial-related imaging, currently delayed due to any "lockdown" strategy adopted in most countries and pandemic-related priorities, is delayed further by post-pandemic imaging capacity limits. [Extracted from the article]