Early changes of PSMA PET expression after initiation of androgen receptor signaling inhibitors in CRPC: an international multicenter retrospective study
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Published on: November 19, 2019
Lena M Unterrainer1,2,3, Andrea Farolfi4,5, Tristan Grogan6
1Ahmanson Translational Theranostics Division, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, Los Angeles, USA. Lena.unterrainer@med.uni-muenchen.de.
Background:
An increase of PSMA expression under androgen receptor signaling inhibitors (ARSi) measured on PSMA PET was reported: However, results were inconsistently reproduced clinically and the frequency and timing of the PSMA expression modulation by ARSi remains unknown.
Methods:
In this multicenter retrospective study, we aimed at assessing in patients with CRPC the influence of ARSi early after initiation (≤ 30 days) on PSMA expression at the whole-body (WB) level by using WB PSMA PET quantitative parameters. (m)CRPC patients from 5 international sites who underwent a PSMA PET prior to (PET1) and early (< 30 days) after (PET2) ARSi initiation were included. WB-PSMA PET quantitative parameters (PSMA-positive WB-tumor volume (TV), WB-SUVmax, WB-SUVmean) and PSA changes between PET1 and PET2 (PSA1/PSA2) were evaluated. Changes of WB-TV / WB-SUVmax/mean between PET1 and PET2 were considered significant if ≥ 30% of increase or decrease.
Results:
Fifty-six patients who initiated ARSi treatment were included. 30/56 (53.6%) were treated with an ARSi for the first time, 26/56 (41.1%) were previously treated with another ARSi agent and 29/56 (51.9%) received prior chemotherapy. 10/56 (17.9%) had a significantly increasing PSA of ≥ 25% between PET1 and PET2. 15/56 (27%), 14/56 (25%) and 1/56 (1.8%) patients had a significantly increasing WB-TV, WB-SUVmax or WB SUVmean of ≥ 30% between PET1 and PET2, respectively. The patients with significant WB-TV increase (n = 15) and with significant WB SUVmax increase (n = 14) did not differ significantly from the ones with stable or decreased WB-TV (n = 41) or WB-SUVmax (n = 42) in their clinical characteristics or their PSA responses.
Conclusions:
In this analysis of patients with early PSMA PET follow-up after ARSi initiation, we observed a PSMA-upregulation by WB-PET imaging in 25% of the patients. Further studies are needed to better understand the potential synergistic and / or additive effects of AR- and PSMA-targeted approaches.
Clinical Trial Number:
Not applicable.
