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ConclusionsThese results support the use of 68 Ga-PSMA PET/CT for primary staging of prostate cancer. Increasing PSA level, ISUP grade and radiological staging with mpMRI were all statistically significant prognostic factors for metastasis on both univariate and multivariate analysis. KeywordsPET PSMA scan, primary staging, #PCSM, #ProstateCancer [Corrections added on 23 January 2020 after online publication: A new reference (23) has been added. In the Discussion section, the reference cue for the cross-sectional retrospective analysis of 220 men with newly diagnosed prostate cancer has been corrected, and the information relating to skeletal metastasis based on PSA levels has been corrected.]

Purpose:Multiparametric magnetic resonance imaging (mpMRI) fails to identify some men with significant prostate cancer. Prostate-specific membrane antigen positron emission tomography/computerized tomography (PSMA PET/CT) is recommended for staging of prostate cancer, but its additional benefit above mpMRI alone in local evaluation for prostate cancer is unclear. The study aim was to evaluate the ability of mpMRI and PSMA PET/CT individually and in combination, to predict tumor location and Gleason score ≥3+4 on robot-assisted laparoscopic radical prostatectomy (RALP) histology.Materials and Methods:We retrospectively reviewed 1,123 men with a preoperative mpMRI and 68Ga-PSMA PET/CT prior to a RALP. Tumor locations were collected from both imaging modalities and compared to totally embedded prostate histology. Lowest apparent diffusion coefficient value on mpMRI and the highest maximum standardized uptake value (SUVmax) on 68Ga-PSMA PET/CT were collected on the index lesions to perform analysis on detection rates.Results:Median prostate specific antigen was 6. Median Gleason score on biopsy and RALP histology was 4+3. The index lesion and multifocal tumor detection were similar between mpMRI and 68Ga-PSMA PET/CT (p=0.10; p=0.11). When combining mpMRI and 68Ga-PSMA PET/CT, index Gleason score ≥3+4 cancer at RALP was identified in 92%. Only 10% of patients with Gleason score ≤3+4 on biopsy with an SUVmax <5 were upgraded to ≥4+3 on RALP histology, compared to 90% if the SUVmax was >11.Conclusions:The addition of a diagnostic 68Ga-PSMA PET/CT to mpMRI can improve the detection of significant prostate cancer and improve the ability to identify men suitable for active surveillance.

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Objectives To determine the proportion of solitary rib lesions on pre‐treatment 68Gallium‐labelled prostate‐specific membrane antigen (PSMA)/computed tomography (CT) scans in men with prostate cancer that are malignant and examine any predictive factors. Patients and methods This retrospective single tertiary referral institution cohort study of men reviewed the results of 68Ga‐PSMA‐11 positron emission tomography (PET)/CT scans performed for primary staging prior to treatment of prostate cancer from July 2014 to September 2019. Men with PSMA uptake outside the prostate in only the rib lesion were included. A solitary rib lesion was considered to be malignant if it increased in size on follow‐up imaging. A lesion was considered benign if the prostate‐specific antigen (PSA) level remained <0.1 µg/L following a radical prostatectomy (RP), <2 µg/L above nadir following radiotherapy (RT) as per the Phoenix criteria, histology was benign on rib biopsy, or follow‐up imaging showed no growth of the rib lesion. If a lesion did not meet these criteria it was considered indeterminate. Results A total of 62 men had PSMA uptake in a solitary rib lesion; 54 went on to have RPs and eight underwent RT. In all, 61 of the men (98.4%) met the criteria for a benign rib lesion. Only one man had a false‐negative malignant lesion. This man had a rib lesion with a low maximum standardised uptake value (SUVmax) of 2.21 reported as benign, but the postoperative PSA level was 0.67 µg/L and the rib lesion progressed on follow‐up imaging, with development of widespread metastases. Of the benign rib lesions, there were four false positives reported as possible metastases. Three had percutaneous rib biopsies, two of which came back with benign histology and one was indeterminate. The indeterminate biopsy patient had a RP and his postoperative PSA level was <0.1 µg/L. A total of 43 (69.4%) men with benign rib lesions had a SUVmax greater than the SUVmax of the malignant lesion. Conclusion To our knowledge, this is the first cohort study of men with PSMA‐avid solitary rib lesions on pre‐treatment 68Ga‐PSMA PET/CT staging scans for prostate cancer. Our results indicate that the vast majority of these lesions have low‐intensity uptake and are benign. Intervention to confirm this is not usually required.