Ribociclib as First-Line Therapy for HR-Positive, Advanced Breast Cancer

N Engl J Med. 2016 Nov 3;375(18):1738-1748. doi: 10.1056/NEJMoa1609709. Epub 2016 Oct 7.

Abstract

Background: The inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) could potentially overcome or delay resistance to endocrine therapy in advanced breast cancer that is positive for hormone receptor (HR) and negative for human epidermal growth factor receptor 2 (HER2).

Methods: In this randomized, placebo-controlled, phase 3 trial, we evaluated the efficacy and safety of the selective CDK4/6 inhibitor ribociclib combined with letrozole for first-line treatment in 668 postmenopausal women with HR-positive, HER2-negative recurrent or metastatic breast cancer who had not received previous systemic therapy for advanced disease. We randomly assigned the patients to receive either ribociclib (600 mg per day on a 3-weeks-on, 1-week-off schedule) plus letrozole (2.5 mg per day) or placebo plus letrozole. The primary end point was investigator-assessed progression-free survival. Secondary end points included overall survival, overall response rate, and safety. A preplanned interim analysis was performed on January 29, 2016, after 243 patients had disease progression or died. Prespecified criteria for superiority required a hazard ratio of 0.56 or less with P<1.29×10-5.

Results: The duration of progression-free survival was significantly longer in the ribociclib group than in the placebo group (hazard ratio, 0.56; 95% CI, 0.43 to 0.72; P=3.29×10-6 for superiority). The median duration of follow-up was 15.3 months. After 18 months, the progression-free survival rate was 63.0% (95% confidence interval [CI], 54.6 to 70.3) in the ribociclib group and 42.2% (95% CI, 34.8 to 49.5) in the placebo group. In patients with measurable disease at baseline, the overall response rate was 52.7% and 37.1%, respectively (P<0.001). Common grade 3 or 4 adverse events that were reported in more than 10% of the patients in either group were neutropenia (59.3% in the ribociclib group vs. 0.9% in the placebo group) and leukopenia (21.0% vs. 0.6%); the rates of discontinuation because of adverse events were 7.5% and 2.1%, respectively.

Conclusions: Among patients receiving initial systemic treatment for HR-positive, HER2-negative advanced breast cancer, the duration of progression-free survival was significantly longer among those receiving ribociclib plus letrozole than among those receiving placebo plus letrozole, with a higher rate of myelosuppression in the ribociclib group. (Funded by Novartis Pharmaceuticals; ClinicalTrials.gov number, NCT01958021 .).

Publication types

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

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Aminopyridines / administration & dosage*
  • Antineoplastic Combined Chemotherapy Protocols / adverse effects
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / pathology
  • Disease-Free Survival
  • Double-Blind Method
  • Drug Administration Schedule
  • Female
  • Humans
  • Kaplan-Meier Estimate
  • Letrozole
  • Middle Aged
  • Neoplasm Staging
  • Nitriles / administration & dosage*
  • Purines / administration & dosage*
  • Receptor, ErbB-2
  • Receptors, Estrogen
  • Receptors, Progesterone
  • Triazoles / administration & dosage*

Substances

  • Aminopyridines
  • Nitriles
  • Purines
  • Receptors, Estrogen
  • Receptors, Progesterone
  • Triazoles
  • Letrozole
  • ERBB2 protein, human
  • Receptor, ErbB-2
  • ribociclib

Associated data

  • ClinicalTrials.gov/NCT01958021