(UroToday.com) The American Urological Association (AUA) 2025 Annual Meeting, held in Las Vegas, NV, was host to an advanced prostate cancer moderated poster session. Dr. Armando Stabile presented a study of the impact of previous pelvic radiotherapy on PSMA PET outcomes in patients experiencing biochemical recurrence following a radical prostatectomy and its implications for the optimal timing of re-staging.
Given that it remains unknown whether a history of pelvic radiotherapy impacts PSMA PET detection rates in the biochemically recurrent setting, the objective of this study was to evaluate the impact of prior pelvic radiotherapy on PSMA PET detection rates and the distribution of positive findings.
This was a multicenter, retrospective analysis of 441 patients with biochemical recurrence following a radical prostatectomy who were staged with a PSMA PET between 2016 and 2023. The study investigators initially developed a multivariable logistic regression model that incorporated PSA at PET, pathologic Gleason Score and nodal stage to predict the odds of a positive PSMA PET in patients without a history of prior pelvic radiotherapy. An interaction term was incorporated to evaluate whether the risk of a positive PSMA PET varied by history of prior pelvic radiotherapy. The predicted versus observed rates of positive PSMA PET scans were plotted, stratified by prior history of radiotherapy use.
The median PSA at PSMA PET was 0.5 ng/ml. Almost half of patients had pathologic Grade Group 4–5 disease, and 22% had pathologic nodal disease. 38% of patients had received radiotherapy prior to the PSMA PET scan. 55% of PSMA PET scans were positive, with the following distribution of visible recurrence sites:
- Local recurrence: 12%
- miN1: 28%
- miM1b: 38%
- miM1a-c: 22%
The multivariable model for predicting a positive PSMA PET demonstrated a c-index of 72%. Notably, the odds of a positive PSMA PET varied by prior history of previous radiotherapy (p-value for interaction test <0.05). Patients with prior pelvic radiotherapy had increased odds of a positive PSMA PET at a predicted probability of <60%. Sensitivity analyses demonstrated consistent findings, where patients with a history of prior pelvic radiotherapy had increased odds of miM1 positivity at a predicted risk of <45%.
Based on these results, Dr. Stabile concluded that a history of pelvic radiotherapy was associated with increased odds of a positive PSMA PET in the biochemically recurrent setting. He argued that PSMA PET should be performed at lower PSA cutoffs in such patients with a prior history of pelvic radiotherapy.
Presented by: Armando Stabile, MD, Unit of Urology, Division of Oncology, Gianfranco Soldera Prostate Cancer Lab, IRCCS San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
Written by: Rashid K. Sayyid, MD, MSc – Robotic Urologic Oncology Fellow at The University of Southern California, @rksayyid on Twitter during the 2025 American Urological Association (AUA) annual meeting held in Las Vegas, NV, Saturday, April 26 - Tuesday, April 29, 2025