68Ga-prostate specific membrane antigen (PSMA) positron emission tomography (PET) for primary staging of high-risk prostate cancer: a systematic review

To systematically review currently available data on Ga-68-prostate specific membrane antigen (PSMA) positron emission tomography (PET) used for the primary staging of high-risk prostate cancer. We performed critical reviews of EMBASE, Web of Science (including MEDLINE) and Cochrane databases in October 2016 according to the Preferred Reporting Items for Systematic Review and Meta-analysis statement. We included studies that utilized Ga-68-PSMA PET for primary staging of prostate cancer. Quality was assessed using the Critical Appraisal Skills Programme checklist for diagnostic test studies. Following our systematic search strategy, 12 studies were included for assessment. These studies comprised a total of 322 patients who underwent Ga-68-PSMA PET scanning for the purpose of primary staging. Only 5 of these studies included histopathologic correlation data. High variation in methodology and outcomes such as sensitivity (range 33-99%) and specificity (> 90%) was seen across all studies. The ability of Ga-68-PSMA PET to detect malignant lesions was evident across studies, with most studies demonstrating increased detection rates with respect to conventional imaging modalities. In the primary staging of prostate cancer Ga-68-PSMA PET appears to outperform traditional imaging modalities. Overall, there are few high-quality studies investigating Ga-68-PSMA PET in this sub-group highlighting the need for formal assessment of PSMA PET in the form of large-volume, prospective studies.