• Phase II study of 26 patients receiving the nonsteroidal AR inhibitor bicalutamide for AR-positive, ER/PR-negative mBC (detected in 12% of ER/PR-neg cases).
• Clinical benefit rate: 21%; median PFS: 12 weeks.

A small proportion of patients with metastatic breast cancer — including some with triple-negative disease — have tumors expressing the androgen receptor, and this small exploratory study from Memorial examined the potential role of antiandrogens in this population. Although no RECIST objective responses were reported, encouraging rates of clinical benefit were observed with the first-generation antiandrogen bicalutamide. This experience has in part led Memorial to further its androgen-related initiative. However, their focus appears to have shifted toward the “super” antiandrogen enzalutamide, which they are currently evaluating in a Phase I/II trial. Enzalutamide has a more complex mechanism of action than first-generation agents, and in prostate cancer many believe it should be the preferred first-line endocrine treatment for patients with castration-resistant tumors. Whether similar benefits with this agent will be seen in breast cancer is speculative, but based on the relatively benign side-effect profile of the drug and the lack of need for concomitant corticosteroids, trial participation would seem to be an attractive option.