This lead to the FDA granting accelerated approval to palbociclib for use in combination with letrozole for the treatment of postmenopausal women in the first line metastatic setting in ER +, human epidermal growth factor receptor 2 (HER2)-negative breast cancer [44] and increased interest in examining this agent in other solid tumors including lung. This evidence concerns the gene ERBB2 and breast carcinoma.