Primary Objective:
* To evaluate the expression of PSMA via 18F-DCFPyL PSMA-based PET/CT in patients with metastatic HER2-negative, AR-positive breast cancer. Expression of PSMA will be quantified using PSMA-based PET imaging using a novel agent, 18F-DCFPyL, as a non-invasive imaging biomarker of tumor neovasculature in HER2-negative, AR-positive metastatic breast cancer.
Secondary Objectives:
* PSMA PET will be compared with the expression of PSMA in CTCs and diagnostic metastatic tissue from patients with HER2-negative, AR-positive metastatic breast cancer.
* PSMA expression will be correlated with clinical benefit (objective response and progression-free survival) to bicalutamide and ribociclib for patients enrolled in NCT03090165.
