Publications

Abstract

Introduction:68Ga PSMA PET CT (PSMA) is increasingly used in men with PSA failure post radical prostatectomy (RP) to triage those who will benefit from salvage radiation treatment (SRT). This study examines the value of PSMA informed SRT in improving treatment outcomes in the context of biochemical failure post RP. Methods: We analysed men with rising PSA post RP with PSA readings between 0.05 and 1.0 ng/ml, considered eligible for SRT at the time of PSMA. For each patient, clinical and pathological features as well as scan results, including site of PSMA positive disease, number of lesions, and a certainty score were documented. Using medical records, subsequent management, including SRT, and most recent PSA was recorded. Treatment response was defined as both PSA </= 0.1ng/ml and >50% reduction in PSA. Multivariate logistic regression analysis was performed for association of clinical variables and treatment response to SRT. Results: 164 men were included. PSMA was positive in 61% (n = 102/164): 38/102 in the prostatic fossa, 41/102 in pelvic nodes, and 23/102 distantly. 24 patients received ADT and were excluded for outcomes analysis. In total 99/146 received SRT with median follow up 10.5 (IQR 6-14) months. Overall treatment response after SRT was 72% (n = 71/99). 44% (n = 27/60) of patients with a negative PSMA underwent SRT while 56% (33/60) did not. Men with a negative PSMA who received SRT, 85% (n = 23/27) demonstrated a treatment response, compared to further PSA increase in 65% (22/34) in those not treated. In 36/99 with disease confined to the prostate fossa on PSMA, 83% (n = 29/36) responded to SRT. In total 26/99 men had nodal disease on PSMA, of whom 61% (n = 16/26) had treatment response following SRT. On multivariate logistic regression analysis, PSMA and serum PSA significantly correlated with treatment response, while pT stage, Gleason score and surgical margin status did not. Conclusion: PSMA PET is independently predictive of treatment response to SRT, and stratifies men into a high treatment response to SRT (negative or fossa confined PSMA) versus men with poor response to SRT (nodes or distant disease PSMA). In particular, a negative PSMA PET predicts a high response to salvage fossa radiotherapy.