Prostate-Specific Membrane Antigen PET-CT findings in biochemical relapse after prostatectomy
Artingstall 1, A. Mohamed 1, M. Beresford 1
(1) Royal United Hospital, Bath – United Kingdom
Objective:
Surveillance for recurrence of prostate cancer after radical treatment is most often performed by measuring Prostate Specific Antigen (PSA) levels. Prostate-Specific Membrane Antigen (PSMA) PET-CT is increasingly used to assess patients with detectable PSA relapse, identifying sites of persistent or recurrent prostate cancer to inform treatment decisions. We studied PSA levels and PSMA PET-CT results in patients with PSA relapse after radical prostatectomy, to look for patterns of recurrence and at what PSA value this occurred, to inform decision-making on the appropriate PSA threshold to trigger PET-CT imaging.
Methods:
A retrospective review of all patients undergoing PSMA PET-CT at the Royal United Hospital, Bath, UK between August 2020 and February 2024. Only patients undergoing PET in the setting of biochemical PSA relapse after prostatectomy were selected. In these patients, data were collected on the interval between prostatectomy and relapse, Gleason score, pT-stage, presence of R0 resection, PSA level to prompt imaging, whether disease was evident on PET-CT and if present, the sites of disease. We also recorded the management plan that was informed by this imaging.
Results:
37 PSMA PET-CT’s were performed to look for relapse after radical prostatectomy. The lowest PSA to trigger a scan was <0.1ng/ml and the highest PSA was 9.1. 14 patients had no PET-avid disease on the scan. The lowest PSA level in each recurrence group where avid disease was seen ranged from 0.04 (pelvic nodes) to 0.7 (distant metastases). 19 patients had confirmed PET-avid disease on the scan. 16 of these patients had PET-avid disease in the prostate bed, pelvic nodes or both. 10 out of the 16 patients received salvage radiotherapy, and a further 8 patients received prostate bed radiotherapy on the basis of negative or equivocal PSMA PET-CT results.
Conclusions:
PSMA PET-CT was able to detect prostate cancer recurrence even at low PSA values. PET-CT allowed 51% of patients to avoid or delay radiotherapy, either because of non-radically treatable disease or because PSA surveillance could be offered. There was no clear PSA threshold at which PSMA PET-CT scans were unhelpful, so the current practice of scanning when PSA reaches ≥0.2 seems appropriate.