18F-rhPSMA-7 positron emission tomography (PET) for the detection of biochemical recurrence of prostate cancer following radical prostatectomy

Objectives: ¹⁸F-rhPSMA-7 is a new theranostic PSMA-targeting agent which allows fast radiolabeling with ¹⁸F and radiometals and is associated with only minimal renal excretion. This retrospective analysis evaluated the efficacy of ¹⁸F-rhPSMA-7 PET in patients with biochemical recurrence (BCR) of prostate cancer after radical prostatectomy.

Methods: Datasets from patients with non-castrate BCR after radical prostatectomy who underwent ¹⁸F-rhPSMA-7 PET/CT or PET/MRI at our institution between June 2017 and June 2018 were retrospectively reviewed. Images were reviewed by an experienced nuclear medicine physician and all lesions suspicious for recurrent prostate cancer were noted. The detection rates were correlated with patients’ PSA level, primary Gleason score, and prior therapy (androgen deprivation therapy [ADT] and external beam radiation therapy [EBRT]).

Results: Data from 532 patients were reviewed. The patients had a median PSA level of 0.97 (range, 0.01-372) ng/mL. The median injected activity of ¹⁸F-rhPSMA-7 was 332 MBq (range: 142-486), with a median uptake time of 76 (range, 50-220) min. ¹⁸F-rhPSMA-7 PET identified 423 (79.5%) patients with pathological findings. Suspicious lesions were present in 38.5% (15/39) patients with a PSA < 0.2 ng/mL. The detection rates were 63.8% (81/127), 86.5% (90/104), 85.3% (87/102) and 93.8% (150/160) at PSA levels of 0.2-< 0.5, 0.5-< 1 , 1-< 2 and ≥ 2 ng/mL, respectively. ¹⁸F-rhPSMA-7 PET revealed local recurrence in 42.1% (224) patients. Lymph node metastases were present in the pelvis in 41.4% (220), in the retroperitoneum in 16.6% (88) and supradiaphragmatic location in 6.8% (36) patients. Bone and visceral metastases were detected in 21.1% (112) and 4.0% (21) patients, respectively. Detection rates were higher in patients with a Gleason score ≥ 8 compared with scores &#8804; 7 at initial diagnosis (85.0 vs. 77.2%, p<0.0001). Detection was not influenced by prior EBRT (82.2% vs. 77.5%, p=0.185) or ADT within 6 months prior imaging (84.6% vs. 78.0%, p=0.114).

Conclusions: ¹⁸F-rhPSMA-7 PET offers high detection rates in BCR after radical prostatectomy and appear superior to published data for ⁶⁸Ga-PSMA-11.