CCNE1 and neoplasm: Although all biomarker groups derived benefit from palbociclib, those with low tumor CCNE1 expression had a greater response (median PFS for those receiving palbociclib plus fulvestrant, 14.1 months; vs. 4.8 months in those receiving fulvestrant plus placebo) than those with high CCNE1 expression (7.6 months vs. 4.0; palbociclib plus fulvestrant vs. fulvestrant plus placebo, respectively).