Early dynamic imaging in (68)Ga- PSMA-11 PET/CT allows discrimination of urinary bladder activity and prostate cancer lesions

PET/CT with (68)Ga-labelled prostate-specific membrane antigen (PSMA)-ligands has been proven to establish a promising imaging modality in the work-up of prostate cancer (PC) patients with biochemical relapse. Despite a high overall detection rate, the visualisation of local recurrence may be hampered by high physiologic tracer accumulation in the urinary bladder on whole body imaging, usually starting 60 min after injection. This study sought to verify whether early dynamic (68)Ga-PSMA-11 (HBED-CC)PET/CT can differentiate pathologic PC-related tracer uptake from physiologic tracer accumulation in the urinary bladder.

Eighty consecutive PC patients referred to (68)Ga -PSMA-11 PET/CT were included in this retrospective analysis (biochemical relapse: n = 64; primary staging: n = 8; evaluation of therapy response/restaging: n = 8). In addition to whole-body PET/CT acquisition 60 min post injection early dynamic imaging of the pelvis in the first 8 min after tracer injection was performed. SUVmax of pathologic lesions was calculated and time-activity curves were generated and compared to those of urinary bladder and areas of physiologic tracer uptake.

A total of 55 lesions consistent with malignancy on 60 min whole body imaging exhibited also pathologic (68)Ga-PSMA-11 uptake during early dynamic imaging (prostatic bed/prostate gland: n = 27; lymph nodes: n = 12; bone: n = 16). All pathologic lesions showed tracer uptake within the first 3 min, whereas urinary bladder activity was absent within the first 3 min of dynamic imaging in all patients. Suvmax was significantly higher in PC lesions in the first 6 min compared to urinary bladder accumulation (p < 0.001). In the subgroup of PC patients with biochemical relapse the detection rate of local recurrence could be increased from 20.3 to 29.7%.

Early dynamic imaging in (68)Ga-PSMA-11 PET/CT reliably enables the differentiation of pathologic tracer uptake in PC lesions from physiologic bladder accumulation. Performance of early dynamic imaging in addition to whole body imaging 60 min after tracer injection might improve the detection rate of local recurrence in PC patients with biochemical relapse referred for (68)Ga-PSMA-11 PET/CT.

European journal of nuclear medicine and molecular imaging. 2016 Jan 29 [Epub ahead of print]

Christian Uprimny, Alexander Stephan Kroiss, Clemens Decristoforo, Josef Fritz, Boris Warwitz, Lorenza Scarpa, Llanos Geraldo Roig, Dorota Kendler, Elisabeth von Guggenberg, Jasmin Bektic, Wolfgang Horninger, Irene Johanna Virgolini

Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria. ., Department of Nuclear Medicine, Medical University Innsbruck, Anichstrasse 32, 6020, Innsbruck, Austria., Department for Medical Statistics, Informatics and Health Economics, Medical University Innsbruck, Innsbruck, Austria., Department of Urology, Medical University Innsbruck, Innsbruck, Austria.