In the EAP, a total of 242 patients with HR+/HER2- advanced breast disease from 42 centers in the US were assigned to single-arm palbociclib 125 mg/d (3 weeks on, 1 week off) in combination with letrozole 2.5 mg/d (continuous daily dosing) until disease progression. The gene discussed is ERBB2; the disease is breast disorder.