Overall survival results from the randomized phase 2 study of palbociclib in combination with letrozole versus letrozole alone for first‑line treatment of ER+/HER2− advanced breast cancer (PALOMA‑1, TRIO‑18)

Purpose Palbociclib is a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor, approved in combination with endocrine therapy for the treatment of women and men with hormone receptor–positive, human epidermal growth factor receptor 2–negative advanced breast cancer (HR+/HER2− ABC). In the phase 2, open-label, PALOMA-1 trial, palbociclib plus letrozole signifcantly prolonged progression-free survival (PFS) versus letrozole alone (hazard ratio, 0.488; 95% CI 0.319‒0.748; P=0.0004; median PFS, 20.2 vs 10.2 months, respectively) in postmenopausal women with estrogen receptor–positive (ER+)/HER2− ABC. Here, we present the fnal overall survival (OS) and updated safety results. Methods Postmenopausal women with ER+/HER2− ABC were randomized 1:1 to receive either palbociclib (125 mg/day, 3/1 schedule) plus letrozole (2.5 mg/day, continuous) or letrozole alone (2.5 mg/day, continuous). The primary endpoint was investigator-assessed PFS; secondary endpoints included OS and safety. Results A total of 165 patients were randomized. At the data cutof date of December 30, 2016 (median duration of follow-up, 64.7 months), the stratifed hazard ratio for OS was 0.897 (95% CI 0.623–1.294; P=0.281); median OS in the palbociclib plus letrozole and letrozole alone arms was 37.5 and 34.5 months, respectively. The median time from randomization to frst subsequent chemotherapy use was longer with palbociclib plus letrozole than letrozole alone (26.7 and 17.7 months, respectively). The most frequently reported adverse event in the palbociclib plus letrozole arm was neutropenia (any grade, 75%; grade 3 or 4, 59%). Conclusions Palbociclib plus letrozole treatment led to a numerical but not statistically signifcant improvement in median OS. Pfzer Inc (NCT00721409

Overall survival results from the randomized phase II study of palbociclib (P) in combination with letrozole (L) vs letrozole alone for frontline treatment of ER+/HER2–advanced breast cancer (PALOMA-1; TRIO-18)

Background: Preclinical data identified a synergistic role for P and hormone blockade in blocking growth of ER+ breast cancer (BC) cell lines. PALOMA-1 was an open-label phase II trial comparing progression-free survival (PFS) in patients (pts) with advanced ER+/HER2–BC treated with P+ L or L alone. Median PFS increased with addition of P to L to 20.2 mos (vs 10.2 mos with L alone; HR= 0.488), with an acceptable safety profile, leading to accelerated approval by the US FDA. These results were confirmed in the phase 3 ..