Outcomes for [177Lu]Lu-PSMA-617 with and Without Concurrent Use of Androgen Receptor Pathway Inhibitors in Patients with Metastatic Castration-resistant Prostate Cancer

Background and objective

Large clinical trials, including VISION, have established the safety of combining [¹⁷⁷Lu]Lu-PSMA-617 with an androgen receptor pathway inhibitor (ARPI). Most patients receiving [¹⁷⁷Lu]Lu-PSMA-617 in the real-world setting have already progressed on an ARPI. This study aimed to assess the efficacy of [¹⁷⁷Lu]Lu-PSMA-617 in patients with and without the concurrent use of an ARPI.

Methods

We analyzed data from the Mayo Clinic Rochester radiopharmaceutical database, focusing on patients with metastatic castration-resistant prostate cancer (mCRPC) who had progressed after prior exposure to an ARPI and started treatment with [¹⁷⁷Lu]Lu-PSMA-617 between March 2022 and March 2023. Patients receiving concurrent ARPIs (abiraterone, enzalutamide, apalutamide, or darolutamide) were identified. Baseline characteristics were compared using Mann-Whitney U test and chi-square test. Outcomes of interest included prostate-specific antigen (PSA) 50 response, median number of cycles, and overall survival (OS) from the start of [¹⁷⁷Lu]Lu-PSMA-617, analyzed using Kaplan-Meier estimates and multivariate Cox regression.

Key findings and limitations

Among 256 patients, 106 (41.4%) received an ARPI with [¹⁷⁷Lu]Lu-PSMA-617. Those receiving an ARPI had lower baseline PSA levels (3.4 vs 29.7 ng/ml, p < 0.001) and lower rates of bone (77.4% vs 87.4%, p = 0.035) and visceral (18.9% vs 34%, p = 0.008) metastases. While patients on ARPIs were more likely to complete all six cycles of [¹⁷⁷Lu]Lu-PSMA-617 (63.2% vs 48.7%, p < 0.001), PSA50 response rates were similar (49.1% vs 47.3%, p = 0.786). Median OS was longer with concurrent ARPI use (not reached vs 15.3 mo, p < 0.001), but this difference was not significant on a multivariate analysis (hazard ratio = 1.03 [95% confidence interval: 0.68–1.55], p = 0.891) after accounting for baseline differences in other prognostic variables. Limitations include its single-center, retrospective design and a lack of standardized radiographic response assessment.

Conclusions and clinical implications

Among men with mCRPC previously exposed to an ARPI, continuation of the ARPI with [¹⁷⁷Lu]Lu-PSMA-617 did not improve PSA50 response rates or OS after adjusting for cohort imbalances in known prognostic factors. Further post hoc analyses using large clinical trial data are needed.