Introduction:

Prostate-specific membrane antigen (PSMA) PET imaging is recommended for patients with biochemical recurrence (BCR) after radical prostatectomy (RP). This study describes the early clinical impact of PSMA-PET compared to conventional imaging (CT, MRI, or bone scintigraphy) in a contemporaneous period.

Methods:

This retrospective study includes patients with BCR after RP (defined as PSA ≥ 0.2 after undetectable PSA post-operatively) who underwent PSMA-PET or conventional imaging between 2010-2023. The primary outcome was positive detection rate. The secondary outcomes were rates of salvage treatment (XRT and/or ADT) and second BCR. Cox proportional hazards modeling was used to predict risk of salvage treatment and second BCR. 

Results:

217 post-radical prostatectomy patients were included in this study. Of the 146 patients who underwent PSMA-PET and the 71 who underwent conventional imaging (CT, MRI, bone scintigraphy), 77 (52.7%) and 7 (9.9%) patients had positive imaging findings at a median PSA value of 0.23 (IQR 0.21-0.33) and 0.25 (IQR 0.25-0.44), respectively (p=0.36). 48 patients received both imaging modalities. Of these, 4 had positive results in both PSMA-PET and conventional imaging, while 26 were positive for PSMA-PET only, and 2 were positive on conventional imaging only. Patients underwent salvage therapy at lower median PSA values in the PSMA-PET group (0.40 vs 0.51, p<0.01). On unadjusted survival analysis, there were no differences in salvage therapy rates (Figure 1) or second BCR rates (Figure 2) between PSMA-PET or conventional imaging groups. On multivariable Cox proportional hazards modeling, year of PSA recurrence (HR 0.89, 95% CI 0.84-0.95), BMI (HR 1.45, 95% CI 1.02-2.07), ≥GG3 (HR 1.77 95% CI 1.3-2.4), and undetectable PSA≥6 months after RP (HR 0.50 95% CI 0.34-0.72) were associated with salvage treatment, however, imaging modality was not. High genomic risk scores (Decipher>0.60) may be associated with second BCR (HR 2.03 95% CI 0.99-4.18, p=0.05) while other variables did not.

Conclusion:

PSMA-PET usage increased over the period of this study with higher sensitivity and with lower median values before salvage thrapy. Imaging modality however did not predict rates of salvage therapy or second BCR, while other clinical risk factors such as adverse pathology and high genomic risk score did. Analysis with a historical cohort is pending.

Funding: UCSF Goldberg-Benioff Program in Translational Cancer Biology