Treatment Effect Of Palbociclib (Pal) Plus Endocrine Therapy (Et) By Prognostic And Intrinsic Subtype: A Joint Analysis Of Paloma2 And Paloma3

1023Background: PAL + ET showed significant progression-free survival (PFS) benefit vs ET alone in patients (pts) with HR+/HER2- advanced breast cancer (ABC) in PALOMA2 (PAL2) and PALOMA3 (PAL3). Exploratory analyses were conducted on pts who received neo/adjuvant therapy to evaluate the effect of initial disease-free interval (DFI) in PAL3 or treatment-free interval (TFI) in PAL2 on PFS outcomes. Other analyses assessed luminal (Lum) subtype on PAL efficacy. Methods: Pre/postmenopausal pts whose disease has progressed after prior ET (PAL3; N = 521) and postmenopausal pts previously untreated for ABC (PAL2; N = 666) were randomized 2:1 to receive ET (fulvestrant [F] 500 mg or letrozole [L] 2.5mg/d, respectively) + PAL (125 mg/d, 3 wk on/1 wk off) or placebo (PBO). Median follow up was 14 mos (PAL3; 23Oct2015) and 37 mos (PAL2; 31May2017). DFI in PAL3 was calculated as time between first diagnosis of BC and disease recurrence and TFI in PAL2 as time between end of any neo/adjuvant therapy and relapse. Subp...