Purpose: Since the introduction of positron emission tomography (PET) imaging with (68)Ga-PSMA-HBED-CC (=(68)Ga-DKFZ-PSMA-11), this method has been regarded as a significant step forward in the diagnosis of recurrent prostate cancer (PCa). However, published data exist for small patient cohorts only. The aim of this evaluation was to analyse the diagnostic value of (68)Ga-PSMA-ligand PET/CT in a large cohort and the influence of several possibly interacting variables.
Methods: We performed a retrospective analysis in 319 patients who underwent (68)Ga-PSMA-ligand PET/CT from 2011 to 2014. Potential influences of several factors such as prostate-specific antigen (PSA) level and doubling time (DT), Gleason score (GSC), androgen deprivation therapy (ADT), age and amount of injected tracer were evaluated. Histological verification was performed in 42 patients after the (68)Ga-PSMA-ligand PET/CT. Tracer uptake was measured in 901 representative tumour lesions.
Results: In 82.8% of the patients at least one lesion indicative of PCa was detected. Tumor-detection was positively associated with PSA level and ADT. GSC and PSA-DT were not associated with tumor-detection. The average maximum standardized uptake value (SUVmax) of tumour lesions was 13.3 ± 14.6 (0.7-122.5). Amongst lesions investigated by histology, 30 were false-negative in 4 different patients, and all other lesions (n = 416) were true-positive or true-negative. A lesion-based analysis of sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) revealed values of 76.6%, 100%, 91.4% and 100%. A patient-based analysis revealed a sensitivity of 88.1%. Of 116 patients available for follow-up, 50 received local therapy after (68)Ga-PSMA-ligand PET/CT.
Conclusion: (68)Ga-PSMA-ligand PET/CT can detect recurrent PCa in a high number of patients. In addition, the radiotracer is highly specific for PCa. Tumour detection is positively associated with PSA and ADT. (68)Ga-PSMA-ligand PET/CT can help delay systemic therapy of PCa.