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Introduction: Clinical and biochemical assessment and biopsies can miss clinically significant prostate cancers (csPCa) in up to 20% of patients and diagnose clinically insignificant tumours leading to overtreatment. This retrospective study analyses the accuracy of 18F‐DCFPyL PET/CT in detecting csPCa as a primary diagnostic tool and directly compares it with mpMRI prostate in treatment‐naive patients. The two modalities are then correlated to determine whether they are better in combination, than either alone. Methods: This is a retrospective dual‐institution study of patients who underwent contemporaneous MRI and PSMA‐PET between January 2017 and March 2020 with histologic confirmation. The images were re‐reviewed and concordance between modalities assessed. Results were compared with histopathology to determine the ability of MRI and PSMA‐PET to detect csPCA. Results: MRI and PSMA‐PET detected the same index lesion in 90.8% of cases with a kappa of 0.82. PET detected an additional 6.2% of index lesions which were MRI occult. MRI detected an additional 3.1% which were PET occult. No additional csPCa was identified on pathology which was not seen on imaging. The sensitivity of PSMA‐PET in detecting csPCa is 96.7% and that of MRI is 93.4% with no statistically significant difference between the two (P = 0.232). Both modalities detected all four cases of non‐csPCa with these being considered false positives. Conclusion: Both mpMRI and 18F‐DCFPyL‐PSMA‐PET/CT have high sensitivity for detecting csPCa with high agreement between modalities. There were no synchronous csPCa lesions detected on pathology that were not detected on imaging too. [ABSTRACT FROM AUTHOR]

Purpose: With increasing use of PSMA PET/CT in the staging and restaging of prostate cancer (PCa), the identification of non-prostate cancer tumours (NPCaT) has become an increasing clinical dilemma. Atypical presentations of PSMA expression in prostate cancer and expression in NPCaT are not well established. Understanding the normal and abnormal distribution of PSMA expression is essential in preparing clinically relevant reports and in guiding multidisciplinary discussion and decisions. Methods: Retrospective review of 1445 consecutive 18F-DCFPyL PSMA PET/CT studies by experienced radiologists and nuclear medicine physicians. Lesions indeterminate for PCa were identified. Correlation was made with patient records, biopsy results, and dedicated imaging. Lesions were then categorized into four groups: 1. Confirmed prostate cancer, metastases, 2. NPCaT 3. Benign, and 4. Indeterminate lesions. Results: 68/1445 patients had lesions atypical for prostate cancer metastases. These comprised 8/68 (11.8%) atypical prostate cancer metastases, 17/68 (25.0%) NPCaT, 29/68 (42.6%) indeterminate, and 14/68 (20.6%) benign. In the context of the entire cohort, these are adjusted to 8/1445 (0.6%), 17/1445 (1.2%), 29/1445 (2.0%), and 14/1445 (1.0%) respectively. With the exception of Renal Cell Carcinoma (RCC), NPCaT demonstrated no or low PSMA expression. A similar trend was also observed for indeterminate and benign lesions. Conversely, most atypical PCa metastases demonstrated intermediate or high PSMA expression. Conclusion: 18F-DCFPyL PSMA PET/CT detection of NPCaT is low. Lesions demonstrating intermediate to high PSMA expression were exclusively prostate cancer metastases, aside from RCC, and lesions detected in organs with high background expression. [ABSTRACT FROM AUTHOR]

Objectives: To assess the correlation of pathological radical prostatectomy (RP) specimen features and prostate‐specific antigen (PSA) characteristics to imaging findings on subsequent 18F‐DCFPyL positron emission tomography/computed tomography (PET/CT) in patients with biochemical failure (BF). Patients and Methods: Retrospective analysis of combined 18F‐DCFPyL PET/CT database of patients from centres in Australia and New Zealand was performed. A total of 205 patients presenting with BF after RP were included in this study. Imaging findings on 18F‐DCFPyL PET/CT were recorded and correlated with the PSA characteristics at BF and pathological features of the original tumour. Results: Of the 205 patients, 120 (58.5%) had evidence of abnormal prostate‐specific membrane antigen (PSMA) expression compatible with recurrent prostate cancer. Increasing PSA velocity (P = 0.01), International Society of Urological Pathology (ISUP) Grade Group (P = 0.02), lymphovascular invasion (P = 0.05) and nodal positivity (P = 0.02) at the time of RP were more likely to demonstrate PSMA positivity. Multivariable logistic regression revealed a higher PSA level prior to PSMA PET/CT (P < 0.01), adjuvant radiotherapy (P = 0.09), Gleason score ≥8 (P < 0.01) and nodal positivity (P = 0.05) were all predictive of PSMA positivity. Conclusion: 18F‐DCFPyL PET/CT positivity, both generally and site specific, correlates with PSA and RP pathological factors. Our results echo cohorts focussing on post‐RP patients, those imaged with 68Ga‐PSMA and those concerning biochemical persistence. Nomograms that include risk factors for 'PSMA‐positive recurrence' in the BF population may increase the catchment of patients with disease confined to the prostate bed or pelvis who have a greater probability of prolonged disease‐free survival. [ABSTRACT FROM AUTHOR]