Results of a randomized phase 2 study of PD 0332991, a cyclin-dependent kinase (CDK) 4/6 inhibitor, in combination with letrozole vs letrozole alone for first-line treatment of ER+/HER2- advanced breast cancer (BC). Publication Number S1-6 2012 San Antonio Breast Cancer Symposium (SABCS) - Finn, R (San Antonio, 2012)