ERBB2 and breast carcinoma: More recently, the combination of palbociclib and the estrogen antagonist, fulvestrant, increased median PFS in women with advanced HR-positive, HER2-negative breast cancer who had progressed on prior endocrine therapy (9.2 months in the palbociclib and fulvestrant arm vs. 3.8 months in the placebo and fulvestrant arm (HR 0.422, 95% CI 0.318 – 0.560, P < 0.000001) [10].