Presentation Authors: Matthew Roberts*, Peter Donato, Andrew Morton, Samuel Kyle, Geoff Coughlin, Rachel Esler, Nigel Dunglison, Robert Gardiner, John Yaxley, Brisbane, Australia
Introduction: 68Ga Prostate specific membrane antigen (PSMA) positron emission tomography (PET) represents an emerging method for primary prostate cancer staging of regional and distant metastases. Limited data on primary tumour characterisation appear promising, hence this study sought to assess the accuracy of 68Ga-PSMA PET/CT compared with multiparametric MRI (mpMRI) relative to prostate biopsy histopathology.
Methods: A retrospective study was performed to include patients who underwent mpMRI, 68Ga-PSMA PET/CT and prostate biopsy between June 2014 and July 2017 in an academic, tertiary referral centre where a mpMRI-based triage pathway is routinely used. Use of 68Ga-PSMA PET/CT was performed more commonly in recent years with wider acceptance and incorporation into clinical practice. Standard clinical parameters were collected. Lesions were determined as likely, equivocal or unlikely for mpMRI (PIRADS 4 or 5, PIRADS 3, PIRADS 2 or 1) and 68Ga-PSMA PET/CT (high avidity, low avidity and no avidity), respectively. Analysis was performed on a â€œper patientâ€ and â€œper lesionâ€ basis for assessing lesion concordance between both imaging modalities and prostate biopsy histopathology.
Results: 144 patients (median age 66.5 years, median PSA 8.6 ng/ml) underwent mpMRI, biopsy and 68Ga-PSMA PET/CT. Most patients were intermediate-high risk, with 46.5% and 47.9% of patients demonstrating Gleason 4+3 or Gleason â‰¥ 4+4 on biopsy. On per patient analysis, mpMRI and 68Ga-PSMA PET/CT showed concordance with 83.0% and 92.2% of index lesions respectively. For likely or equivocal lesions, high sensitivity was observed for 68Ga-PSMA PET/CT (98.4%) and mpMRI (90.1%), while per lesion analysis showed 68Ga-PSMA PET/CT (n = 169) identified more histologically-confirmed lesions than mpMRI (n = 149).
Conclusions: 68Ga-PSMA PET/CT is highly sensitive at index lesion identification and detects multifocal disease more accurately than mpMRI. These findings support further research into the role of 68Ga-PSMA PET/CT in pre-treatment staging of prostate cancer.