Theranostics2016 4th Theranostics World Congress 2016 Spotlight on Prostate Cancer (17 abstracts)
First in-man study of 68Ga-THP-PSMA PET in patients with primary prostate cancer: initial results
Michael S. Hofman 1 , Peter Eu 1 , Catherine Mitchell 1 , Phil Blower 2 , Amir Iravani 1 , Declan Murphy 1 , Jennifer Young 2 , Rod J. Hicks 1 & Gregory E. Mullen 2,
1Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia; 2Division of Imaging Sciences and Biomedical Engineering, King’s College London, London, UK; 3Theragnostics Ltd, London, UK.
Ga-68 labelled urea-based inhibitors of the prostate specific membrane antigen (PSMA), such as 68Ga-HBED-PSMA-11, are promising peptides for targeting prostate cancer. The tris(hydroxypyridinone) (THP) ligand rapidly complexes 68Ga3+ at room temperature, at very low concentration and over a wide pH range, making it possible for the direct elution from a 68Ge/68Ga generator into a cold radiopharmaceutical kit in one step without any manipulation. This first in-man study aimed to assess the safety and biodistribution of 68Ga-THP-PSMA (ACTRN: 12615001324505).
Methods: Eight patients with pathologically proven prostate cancer scheduled to undergo prostatectomy were recruited (mean age 61, range 46–71; Gleason score 7–10; PSA mean 7.8, range 5.4–10.6). 68Ga-THP-PSMA was administered with whole body PET/CT imaging performed at multiple time-points from administration to 180 min. Patients were followed-up for 24 h to evaluate for adverse events. All patients proceeded to prostatectomy with PSMA immunohistochemistry performed. Seven patients also underwent pelvic nodal dissection.
Results: No adverse events occurred. Six of eight patients had increased uptake in the prostate above background (at 2 h imaging: average SUVmax 5.1, range 2.4–9.2; volume 4.1 mL, range 1.4–10.4). Physiologic activity was seen in salivary glands, liver, spleen and duodenum; activity in these organs was significantly lower than our experienced with 68Ga-HBED-PSMA11, although direct comparison was not performed. 3+ immunohistochemistry staining was seen in 6 THP-PSMA positive scans, and 1+/ 2+ staining in the 2 THP-PSMA negative scans. Patients with SUVmax over five all had 3+>80% PSMA staining. Pathologic pelvic nodal involvement was identified in two patients although <1 mm in size and therefore not visualised on PET. One patient had focal uptake in sub-cm pelvic nodes without pathologic abnormality; follow-up is awaited to see if this represented sampling error.
Conclusion: 68Ga-THP-PSMA is safe. Focal uptake in prostate adenocarcinoma correlates with high PSMA expression.
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Endocrine Abstracts
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