Disease characteristics and outcome of patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) who received a beta emitter (177Lu-PSMA) after an alpha emitter (radium-223).

Abstract

e17592 Background: Ra-223, a targeted alpha therapy, showed an overall survival (OS) benefit and favorable safety profile in mCRPC pts in a phase 3 trial. 177Lu-PSMA radioligand is an investigational agent for mCRPC. REASSURE (NCT02141438) is a global, prospective, observational study investigating Ra-223 safety in routine clinical practice over 7 years’ follow-up in mCRPC pts. Data from the second prespecified interim analysis (IA) were used to investigate safety and outcomes of pts who received 177Lu-PSMA after Ra-223 therapy. Methods: Data cut-off for the second prespecified IA was March 2019, and included pts who had subsequent 177Lu-PSMA after the last Ra-223 dose. Disease characteristics, adverse events (AEs) after last Ra-223 dose, and OS are described. Results: Of 1465 pts overall, 26 received 177Lu-PSMA subsequent to Ra-223. In this subgroup, pts received multiple anticancer therapies prior to 177Lu-PSMA. 13 pts (50%) received Ra-223 as combination therapy at second line (metastatic setting). Pts received a median of six Ra-223 doses. After Ra-223 treatment ended, 3 pts (12%) had drug-related serious AEs, 9 pts (35%) had grade 3/4 bone marrow suppression-relevant hematologic AEs. Median duration of 177Lu-PSMA treatment was 3.5 months. 19 pts (73%) received 177Lu-PSMA as fourth-line therapy or onwards. OS was 28.0 months from start of Ra-223 and 13.2 months from start of 177Lu-PSMA. Conclusions: In this select population receiving a sequence of multiple lines of therapy with different modes of action, grade 3/4 hematologic AEs after Ra-223 were low. Treatment with subsequent 177Lu-PSMA seems feasible, based on duration of 177Lu-PSMA and survival. Clinical trial information: NCT02141438 . [Table: see text]