Association of PSMA PET-derived Parameters and Outcomes of Patients Treated for Oligorecurrent Prostate Cancer

Background Prostate-specific membrane antigen (PSMA) PET is useful in the early detection of oligorecurrent prostate cancer (PCa), but whether PSMA PET parameters can be used to identify patients who would benefit from metastasis-directed therapy (MDT) with radiation or surgery remains uncertain. Purpose To assess the association of PSMA PET parameters with outcomes of patients with oligorecurrent PCa after MDT. Materials and Methods In this retrospective analysis of a single-center phase II trial that enrolled patients with biochemical recurrence of PCa after maximal local therapy and with no evidence of disease at conventional imaging, patients underwent PSMA PET (between May 2017 and November 2021), and unveiled recurrences were treated with MDT. Maximum standardized uptake value (SUVmax) and mean standardized uptake value (SUVmean) and PSMA tumor volume derived using thresholds of 2.5 (SUVmean2.5) and 41% (SUVmean41%), respectively, were recorded for sites of recurrence on PSMA PET scans, and a molecular imaging PSMA score was assigned. These parameters were also corrected for smooth filter and partial volume effects, and the PSMA score was reassigned. Cox proportional hazards models were used to evaluate the relationship between PSMA PET parameters and outcomes. Results A total of 74 men (mean age, 68.3 years ± 6.6 [SD]) with biochemical recurrence of PCa were included. PSMA PET revealed 145 lesions in the entire cohort, of which 125 (86%) were metastatic lymph nodes. Application of the correction factor changed the PSMA score in 88 of 145 lesions (61%). Mean SUVmax, SUVmean2.5, and SUVmean41% were associated with lower risk of biochemical progression (hazard ratio [HR] range, 0.77-0.95; 95% CI: 0.61, 1.00; P = .03 to P = .04). For corrected parameters, mean SUVmax, mean SUVmean2.5, mean SUVmean41%, mean PSMA score, maximum SUVmean2.5, maximum SUVmean41%, and maximum PSMA score were associated with a lower risk of biochemical progression (HR, 0.61-0.98; 95% CI: 0.39, 1.00; P = .01 to P = .04). Conclusion Measured and corrected PSMA PET parameters were associated with biochemical progression in men with oligorecurrent PCa treated with MDT. Clinical trial registration no. NCT03160794 © RSNA, 2023 See also the editorial by Civelek in this issue.