Some good information here (OncLive) about TNBC and CDK4/6 Inhibitors, especially clarifying the different types of TNBC. Scroll toward the bottom of the article.
An excerpt, from Ruth O’Regan, MD. chief of the Division of Hematology, Medical Oncology and Palliative Care within the Department of Medicine and associate director of Clinical Research at the University of Wisconsin Carbone Cancer Center:
However, when you look at TNBC, there is not just 1 type of breast cancer; there are 4 to 6 different types under that triple-negative umbrella. One of them is the luminal AR subtype, which looks like a luminal ER-positive subtype genomically, but is actually ER negative and AR positive. This led to some trials looking at single-agent antiandrogens to treat these AR TNBCs. Overall, both enzalutamide (Xtandi) and bicalutamide (Casodex) produced pretty modest activity. The question become, “How could we make these antiandrogen drugs more effective in these AR-positive TNBCs?”