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Multiple Time-Point 68Ga-PSMA I&T PET/CT for Characterization of Primary Prostate Cancer

Value of Early Dynamic and Delayed Imaging

Schmuck, Sebastian, MD*; Mamach, Martin, MSc; Wilke, Florian; von Klot, Christoph A., MD; Henkenberens, Christoph, MD§; Thackeray, James T., PhD*; Sohns, Jan M., MD*; Geworski, Lilli, PhD; Ross, Tobias L., PhD*; Wester, Hans-Juergen, PhD; Christiansen, Hans, MD§; Bengel, Frank M., MD*; Derlin, Thorsten, MD*

doi: 10.1097/RLU.0000000000001589
Original Articles
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Purpose The aims of this study were to gain mechanistic insights into prostate cancer biology using dynamic imaging and to evaluate the usefulness of multiple time-point 68Ga–prostate-specific membrane antigen (PSMA) I&T PET/CT for the assessment of primary prostate cancer before prostatectomy.

Methods Twenty patients with prostate cancer underwent 68Ga-PSMA I&T PET/CT before prostatectomy. The PET protocol consisted of early dynamic pelvic imaging, followed by static scans at 60 and 180 minutes postinjection (p.i.). SUVs, time-activity curves, quantitative analysis based on a 2-tissue compartment model, Patlak analysis, histopathology, and Gleason grading were compared between prostate cancer and benign prostate gland.

Results Primary tumors were identified on both early dynamic and delayed imaging in 95% of patients. Tracer uptake was significantly higher in prostate cancer compared with benign prostate tissue at any time point (P ≤ 0.0003) and increased over time. Consequently, the tumor-to-nontumor ratio within the prostate gland improved over time (2.8 at 10 minutes vs 17.1 at 180 minutes p.i.). Tracer uptake at both 60 and 180 minutes p.i. was significantly higher in patients with higher Gleason scores (P < 0.01). The influx rate (Ki) was higher in prostate cancer than in reference prostate gland (0.055 [r = 0.998] vs 0.017 [r = 0.996]).

Conclusions Primary prostate cancer is readily identified on early dynamic and static delayed 68Ga-PSMA ligand PET images. The tumor-to-nontumor ratio in the prostate gland improves over time, supporting a role of delayed imaging for optimal visualization of prostate cancer.

From the Departments of *Nuclear Medicine, †Medical Physics and Radiation Protection, ‡Urology and Urological Oncology, and §Radiation and Special Oncology, Hannover Medical School, Hannover; and ∥Department of Pharmaceutical Radiochemistry, Technical University Munich, Munich, Germany.

Received for publication December 13, 2016; revision accepted January 7, 2017.

Conflict of interest and sources of funding: H.-J.W. is a shareholder of Scintomics GmbH, Fürstenfeldbruck, Germany. The other authors have none declared.

Correspondence to: Sebastian Schmuck, MD, Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany. E-mail: Schmuck.Sebastian@mh-hannover.de.

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