ERBB2 and breast cancer: According to the phase II clinical study on palbociclib monotherapy enrolling RB-positive advanced breast cancer patients including 31 patients with hormone receptor (HR)-positive/HER2-negative disease, 2 patients with HR-positive/HER2-positive disease, and 4 patients with HR-negative/HER2-negative disease, clinical benefit (CB) was noted in 7 individuals overall, all of which were HR-positive patients after the treatment of palbociclib at the recommonded dose 125 mg daily on the 3/1 schedule [87].