Prostate-specific membrane antigen (PSMA) PET-CT imaging in the investigation and management of biochemical recurrence in prostate cancer.

Abstract

208 Background: It is estimated that within ten years of primary treatment for prostate cancer up to 40% of patients post radical prostatectomy, and up to 50% of patients post radiotherapy will develop disease recurrence. While monitoring of PSA levels is informative of biochemical recurrence, it may precede radiologically detectable recurrence by months to years, and cannot differentiate local/regional recurrence from systemic disease. This represents a management dilemma for treating physicians. The incorporation of PET probes targeting prostate-specific membrane antigen (PSMA) for prostate cancer shows promise for improving the management of patients with prostate cancer, when used alongside existing imaging techniques, like CT, MRI and bone scans. Methods: Retrospective review of all patients referred from our institution for PSMA imaging was carried out. Baseline clinical features were determined and we analyzed impact of PSMA imaging on management outcomes and survival data. Results: 33 patients referred for 68Ga-PSMA-PET imaging were identified. Median age at diagnosis was 65 years (51 -75). The indication for referral in all patients was biochemical recurrence in the absence of radiological evidence of disease by CT imaging and bone scan. Median PSA at time of referral for PSMA scan was 7.3ug/L (1.4ug/L to 87.7ug/L). 100% of patients (n = 33) were upstaged following PSMA imaging, and 30% (n = 10) had more than one site of metastatic disease identified. Most common sites of metastasis were lymph node and bone. Median number of sites of metastatic disease identified by PSMA imaging was one. These results led to a change in management for 96% patients (n = 32). All patients at the time of this review are alive with a median follow up of 13 months, and median progression-free survival of 11 months. Conclusions: PSMA PET-CT directly led to an alteration in the treatment of the majority of patients in this study. This real world data reflects the growing role of PSMA imaging in influencing clinical decisions for prostate cancer patients with biochemical recurrence. Prospective data from randomized studies are awaited to further validate the role of PSMA PET-CT in this patient cohort.