Sensitivity, Specificity, and Predictors of Positive ⁶⁸Ga-Prostate-specific Membrane Antigen Positron Emission Tomography in Advanced Prostate Cancer: A Systematic Review and Meta-analysis

Context: Positron emission tomography (PET) of ⁶⁸Ga-labelled prostate-specific membrane antigen (⁶⁸Ga-PSMA) is an emerging imaging modality introduced to assess the burden of prostate cancer, typically in biochemically recurrent or advanced disease. ⁶⁸Ga-PSMA PET provides the ability to selectively identify and localize metastatic prostate cancer cells and subsequently change patient management. Owing to its limited history, robust sensitivity and specificity data are not available for ⁶⁸Ga-PSMA PET-positive scans.

Objective: A systematic review and meta-analysis of reported predictors of positive ⁶⁸Ga-PSMA PET and corresponding sensitivity and specificity profiles.

Evidence acquisition: We performed critical reviews of MEDLINE, EMBASE, ScienceDirect, Cochrane Library, and Web of Science databases in April 2016 according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement. Quality was assessed using the Quality Assessment if Diagnostic Accuracy Studies-2 tool. Meta-analysis and meta-regression of proportions were performed using a random-effects model with pre-PET prostate-specific antigen (PSA) levels as the dependent variable. Summary sensitivity and specificity values were obtained by fitting bivariate hierarchical regression models.

Evidence synthesis: Sixteen articles involving 1309 patients were analysed. The overall percentage of positive ⁶⁸Ga-PSMA PET among patients was 40% (95% confidence interval [CI] 19-64%) for primary staging and 76% (95% CI 66-85%) for biochemical recurrence (BCR). Positive ⁶⁸Ga-PSMA PET scans for BCR patients increased with pre-PET PSA. For the PSA categories 0-0.2, 0.2-1, 1-2, and >2 ng/ml, 42%, 58%, 76%, and 95% scans, respectively, were positive. Shorter PSA doubling time increased ⁶⁸Ga-PSMA PET positivity. On per-patient analysis, the summary sensitivity and specificity were both 86%. On per-lesion analysis, the summary sensitivity and specificity were 80% and 97%, respectively.

Conclusions: In the setting of BCR prostate cancer, pre-PET PSA predicts the risk of positive ⁶⁸Ga-PSMA PET. Pooled data indicate favourable sensitivity and specificity profiles compared to choline-based PET imaging techniques.

Patient summary: Positron emission tomography using ⁶⁸Ga-labelled prostate-specific membrane antigen is an emerging radiological technique developed to improve the characterisation of metastatic prostate cancer. We summarised the data available to date and found that this new test provides excellent rates of detection of cancer spread in late-stage prostate cancer.