Presentation Authors: Tobias Maurer*, Hamburg, Germany, Markus Kroenke, Alexander Wurzer, Lena Ulbrich, Lena Jooß, Thomas Horn, Bernhard Haller, Wolfgang Weber, Hans-Jürgen Wester, Matthias Eiber, Munich, Germany
Introduction: While 68Ga-prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is being used for restaging patients with suspected biochemical recurrence (BCR) of prostate cancer, the use of 18F-labeled PSMA ligands is increasing owing to their longer half-life, ease of larger batch production and lower positron range compared with 68Ga-labelled counterparts. Radiohybrid PSMA (rhPSMA) ligands are a new class of theranostic PSMA-targeting agents featuring fast 18F synthesis with utility for labeling with radiometals. This retrospective analysis evaluated the efficacy of 18F-rhPSMA7 PET/CT for imaging BCR of prostate cancer.
Methods: Datasets from 261 consecutive patients with non-castrate BCR after radical prostatectomy who underwent 18F-rhPSMA7 PET/CT between June 2017 and March 2018 were retrospectively reviewed by a nuclear medicine physician. All suspicious lesions were documented and detection rates were correlated with patients&[prime] PSA level, primary Gleason score, and prior therapy (androgen deprivation therapy [ADT] and external beam radiation therapy [EBRT]).
Results: The 261 patients had a median PSA level of 0.96 (range, 0.01 - 400) ng/mL. The median injected activity of 18F-rhPSMA7 was 336 MBq, with a median uptake time of 76 (range, 50 - 220) min. 18F-rhPSMA7-avid lesions were found in 211/261 (80.8%) patients. Among those with PSA < 0.2 ng/mL, 7/22 (31.8%) had suspicious lesions. The detection rate was broadly proportional to PSA; 71.2% (42/59), 86.3% (44/51), 85.7% (42/49) and 95.0% (76/80) at PSA levels of 0.2 - < 0.5, 0.5 - < 1 , 1 - < 2 and â‰¥ 2 ng/mL, respectively. 18F-rhPSMA7 revealed local recurrence in 113 (43.3%) patients. Pelvic lymph node metastases were present in 110 (42.2%), while lymph node metastases were found in retroperitoneal and supradiaphragmatic regions in 45 (17.2%) and 21 (8.0%) patients, respectively. Bone and visceral metastases were detected in 54 (20.7%) and 10 (3.8%) patients, respectively.Detection rates were not influenced by patients&[prime] prior therapy (79.1% among those with prior EBRT vs. 82.1% without prior EBRT, p = 0.55); by ADT in the 6 months preceding imaging (80.6% among patients receiving ADT vs. 80.9% in those not prescribed ADT, p = 0.54); or by primary Gleason score (77.9% among patients with Gleason score â‰¤7 vs. 82.6% for scores â‰¥8, p = 0.38).
Conclusions: 18F-rhPSMA7 PET/CT offers good detection of BCR in men who have undergone radical prostatectomy; detection rates appear favorable compared with those previously reported for 68Ga-PSMA11.