Detection efficacy of hybrid (68)Ga-PSMA ligand PET/CT in prostate cancer patients with biochemical recurrence after primary radiation therapy defined by Phoenix criteria

The aim of this retrospective study was to evaluate the detection rate of Glu-NH-CO-NH-Lys-(Ahx)-[(68)Ga(HBED-CC)] ((68)Ga-PSMA ligand) positron emission tomography/computed tomography (PET/CT) in patients with biochemical recurrent prostate cancer (PC) defined by Phoenix criteria after external beam radiotherapy (EBRT) or brachytherapy as primary treatment. Methods: 118 patients were finally eligible for this retrospective analysis with a median prostate-specific antigen (PSA) of 6.4 ng/mL (range: 2.2-158.4 ng/mL, IQR: 4.2-10.2 ng/mL). 77 and 41 patients had been treated by EBRT or brachytherapy, respectively. Of the 118 patients, 45 were receiving androgen deprivation therapy (ADT) within at least 6 months prior to the PET/CT. The detection rates were stratified by PSA. The influence of primary Gleason score (GS) and ADT was assessed. Relationships between standardized uptake values (SUV) and clinical as well as pathological features in patients with positive findings were analyzed using univariate and multivariable linear regression models. Results: 90.7% (107/118) patients showed pathological findings indicative for tumor recurrence in (68)Ga-PSMA ligand PET/CT. The detection rates were 81.8% (36/44), 95.3% (41/43) and 96.8% (30/31) for PSA of 2 to <5, 5 to <10 and ≥10 ng/mL, respectively (P = 0.0377). (68)Ga-PSMA ligand PET/CT indicated local recurrence in 68/107 patients (63.5%), only distant lesions in 64/107 patients (59.8%) and local recurrence as well as distant lesions in 25/107 patients (23.4%). The detection rate was significantly higher in patients with ADT (97.7%) vs. without ADT (86.3%, P = 0.0381), but independent from primary GS ≥8 (92.0%) vs. ≤7 (90.2%, P = 0.6346). SUVmax and SUVmean were significantly associated with PSA and ADT (P = 0.018 and 0.004 for SUVmax, respectively; P = 0.025 and 0.007 for SUVmean, respectively) . Conclusion:(68)Ga-PSMA ligand PET/CT demonstrates high detection rates in patients with biochemical recurrence of PC after primary radiation therapy. The detection rate was positively associated to increasing PSA as well as concomitant ADT. (68)Ga-PSMA ligand PET/CT enables discrimination of local vs. metastatic disease and thus might have a crucial impact on further clinical management. A major limitation of this study is the lack of histopathological proof in the majority of patients.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2017 Feb 16 [Epub ahead of print]

Ingo Einspieler, Isabel Rauscher, Charlotte Düwel, Markus Krönke, Christoph Rischpler, Gregor Habl, Sabrina Dewes, Armin Ott, Hans-Jürgen Wester, Markus Schwaiger, Tobias Maurer, Matthias Eiber

Technical University of Munich, Germany.