Palbociclib Plus Letrozole as First-Line Therapy in Postmenopausal Asian Women With Metastatic Breast Cancer: Results From the Phase III, Randomized PALOMA-2 Study

J Glob Oncol. 2019 May:5:1-19. doi: 10.1200/JGO.18.00173.

Abstract

Purpose: In PALOMA-2, palbociclib plus letrozole significantly improved progression-free survival (PFS) as initial treatment of estrogen receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer. We assessed the benefit of palbociclib plus letrozole in Asians.

Patients and methods: Of 666 enrolled postmenopausal women with estrogen receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer (no prior treatment of advanced disease), 95 were Asian. Patients were randomly assigned 2:1 to receive palbociclib plus letrozole or placebo plus letrozole. The primary end point was investigator-assessed PFS. Secondary end points were overall survival, objective response, patient-reported outcomes, pharmacokinetics, and safety.

Results: Median PFS was significantly longer in Asian patients who received palbociclib plus letrozole versus placebo plus letrozole (25.7 months [95% CI, 19.2 months to not estimable] v 13.9 months [95% CI, 7.4 to 22.0 months]; hazard ratio, 0.49; 95% CI, 0.27 to 0.87; P = .007). The most common toxicities with palbociclib were hematologic and more frequent among Asians versus non-Asians: neutropenia (any grade, 95.4% v 76.8%; grade 3/4, 89.2% v 62.5%), leukopenia (43.1% v 38.3%; 32.3% v 23.5%), and thrombocytopenia (27.7% v 13.5%; 4.6% v 1.1%). No Asians had febrile neutropenia. Discontinuation rates as a result of adverse events were similar among Asian and non-Asian patients who received palbociclib plus letrozole (10.8% and 9.5%). In Asians, quality of life (QOL) was maintained with no significant differences observed between treatments from baseline in breast cancer-specific QOL and general health status scores. Change from baseline in EuroQol five dimensions index scores was significantly higher with palbociclib plus letrozole (0.013 v -0.069; P = .0132). Geometric mean palbociclib trough concentration values were higher in Asians versus non-Asians (93.8 v 61.7 ng/mL).

Conclusion: Consistent with the overall study population, the addition of palbociclib to letrozole significantly improved PFS in Asians. Hematologic toxicities were more frequent in Asians versus non-Asians but manageable with early dose modifications while maintaining QOL.

Trial registration: ClinicalTrials.gov NCT01740427.

Publication types

  • Clinical Trial, Phase III
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Antineoplastic Combined Chemotherapy Protocols / adverse effects
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / mortality
  • Breast Neoplasms / pathology*
  • Female
  • Humans
  • Letrozole / administration & dosage
  • Letrozole / pharmacokinetics
  • Middle Aged
  • Neoplasm Staging
  • Piperazines / administration & dosage
  • Piperazines / pharmacokinetics
  • Postmenopause
  • Prognosis
  • Pyridines / administration & dosage
  • Pyridines / pharmacokinetics
  • Treatment Outcome

Substances

  • Piperazines
  • Pyridines
  • Letrozole
  • palbociclib

Associated data

  • ClinicalTrials.gov/NCT01740427