Assessing Response to [177Lu]PSMA Radioligand Therapy using modified PSMA PET Progression Criteria

Ziel/Aim Positron emission tomography/computer tomography (PET/CT) targeting the prostate specific membrane antigen (PSMA) plays a key role in staging of patients with prostate cancer (PCa). Moreover, it is not only used for the assessment of adequate PSMA expression of PCa cells before PSMA-targeting radioligand therapy (PSMA RLT) but also for re-staging during the course of therapy to evaluate response to treatment. Whereas no established criteria exist for systematic response evaluation so far, recently proposed PSMA PET Progression (PPP) criteria [ 1 ] might fill this gap. The aim of this study was to assess the feasibility of PPP criteria in patients undergoing PSMA RLT and their prognostic implications. Methodik/Methods In this retrospective analysis, PSMA PET/CT scans of 46 patients acquired before and after completion of PSMA RLT were analyzed separately by two readers using modified PPP criteria (i.e., two new metastases on re-staging PSMA PET/CT, one new metastasis and rise of laboratory values, or visual increase of the tumor volume and rise of laboratory values). After interobserver agreement assessment, consensus results (progressive vs. non-progressive disease) were compared to overall survival (OS) using a multivariate analysis. Ergebnisse/Results Interobserver agreement on modified PPP criteria was substantial (Cohens κ = 0.73). Median OS of all patients (n = 46) was 13.0 [9.8 – 16.2] months. Progression according to modified PPP criteria was found in 32 patients and was a significant (p = <0.001) prognostic marker for OS with a hazard ratio of 17.5 [3.8 - 81.8]. Schlussfolgerungen/Conclusions Response assessment in patients undergoing PSMA RLT using modified PPP criteria are easy to implement, simple to use, reproducible and highly prognostic for OS. Modified PPP criteria should be validated in future prospective trials. Publication History Publication Date: 08 April 2021 (online) © 2021. Thieme. All rights reserved. Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany