The diagnostic value of PET/CT imaging with the 68Ga-labelled PSMA ligand HBED-CC in the diagnosis of recurrent prostate cancer

Purpose Since the introduction of positron emission tomography (PET) imaging with Ga-68-PSMA-HBED-CC (-(68)GaDKFZ-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 Ga-68-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 Ga-68-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 Ga-68-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 lesionswas 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 patientbased analysis revealed a sensitivity of 88.1 %. Of 116 patients available for follow-up, 50 received local therapy after Ga-68-PSMA-ligand PET/CT. Conclusion Ga-68-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. Ga-68-PSMA-ligand PET/CT can help delay systemic therapy of PCa.