[68Ga]Tris(hydroxypyridinone)(THP)-PSMA is a novel radiopharmaceutical for one-step kit-based radiolabelling, based on direct chelation of 68Ga3+ at low concentration, room temperature and over a wide pH range, using direct elution from a 68Ge/68Ga-generator. We evaluated the clinical detection rates of [68Ga]THP-PSMA PET/CT in patients with biochemically recurrent prostate cancer after prostatectomy.
Consecutive patients (n=99) referred for evaluation of biochemical relapse of prostate cancer by [68Ga]THP-PSMA PET/CT were analyzed retrospectively. Patients underwent a standard whole-body PET/CT (1 h p.i.), followed by delayed (3 h p.i.) imaging of the abdomen. PSA-stratified cohorts of positive PET/CT results, standardized uptake values (SUVs) and target-to-background ratios (TBRs) were analyzed, and compared between standard and delayed imaging.
At least one lesion suggestive of recurrent or metastatic prostate cancer was identified on PET images in 52 patients (52.5%). Detection rates of [68Ga]THP-PSMA PET/CT increased with increasing PSA level: 94.1% for a PSA value of ≥10 ng/mL, 77.3% for a PSA value of 2 to <10 ng/mL, 54.5% for a PSA value of 1 to <2 ng/mL, 14.3% for a PSA value of 0.5 to <1 ng/mL, 20.0% for a PSA value of >0.2 to <0.5, and 22.2% for a PSA value of 0.01 to 0.2 ng/mL. [68Ga]THP-PSMA uptake (SUVs) in metastases decreased over time, whereas TBRs improved. Delayed imaging at 3 h p.i. exclusively identified pathologic findings in 2% of [68Ga]THP-PSMA PET/CT scans. Detection rate was higher in patients with a Gleason score ≥8 (P=0.02) and in patients receiving androgen deprivation therapy (P=0.003).
In this study, [68Ga]THP-PSMA PET/CT showed suitable detection rates in patients with biochemical recurrence of prostate cancer and PSA levels ≥ 2 ng /mL. Detections rates were lower than in previous studies evaluating other PSMA ligands, though prospective direct radiotracer comparison studies are mandatory particularly in patients with low PSA levels to evaluate the relative performance of different PSMA ligands.
European journal of nuclear medicine and molecular imaging. 2018 Jan 07 [Epub ahead of print]
Thorsten Derlin, Sebastian Schmuck, Cathleen Juhl, Johanna Zörgiebel, Sophie M Schneefeld, Almut C A Walte, Katja Hueper, Christoph A von Klot, Christoph Henkenberens, Hans Christiansen, James T Thackeray, Tobias L Ross, Frank M Bengel
Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany. ., Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany., ROTOP Pharmaka GmbH, Dresden, Germany., Department of Diagnostic and Interventional Radiology, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany., Department of Urology and Urologic Oncology, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany., Department of Radiation Oncology, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625, Hannover, Germany.