Conditions: Advanced, Metastatic Breast Cancer
Keywords: HR-positive HER2-negative Advanced breast cancer LEE011 Letrozole CDK CDK4 CDK6 CDK4/6 Phase III ER-positive PR-positive Postmenopausal
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 668
Healthy volunteers: no

Brief summary:
The primary purpose of this study was to assess the efficacy of ribociclib, as measured by progression free survival (PFS), in postmenopausal women with hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer who received no prior treatment for advanced disease.

Detailed description:
This was an international, multi-center, randomized, double-blinded, placebo controlled Phase III trial to determine the efficacy and safety of treatment with ribociclib plus letrozole versus placebo plus letrozole in postmenopausal women with HR+, HER2-negative advanced breast cancer who received no prior therapy for advanced disease.

Eligible patients were randomized in 1:1 ratio to either ribociclib group or placebo group. Study treatment continued until disease progression, unacceptable toxicity, death, or discontinuation from the study treatment for any other reason.

Participants who discontinued treatment due to reasons other than disease progression or withdrawal of consent for efficacy follow-up continued to be monitored until disease progression, death, withdrawal of consent, loss to follow-up, or subject/guardian decision (post-treatment efficacy follow-up).

All participants who discontinued treatment were followed for survival until the predetermined number of overall survival (OS) events was reached.

Following the final OS analysis (performed when approximately 400 deaths were recorded) and with protocol amendment 10 (dated 30-Apr-2021), participants and investigators were unblinded and those participants in the placebo arm had the opportunity to cross-over to the ribociclib arm to receive ribociclib plus letrozole. Cross-over was optional and was conducted at the investigator's discretion and upon participant consent.

Arms:
arm 1: Ribociclib 600 mg daily oral (3 weeks on/ 1 week off) in combination with letrozole 2.5 mg daily oral arm 2: Placebo daily oral (3 weeks on/ 1 week off) in combination with letrozole 2.5 mg daily oral.

Participants were unblinded once the final OS analysis was completed and after the implementation of protocol amendment 10 (30-Apr-21) and were given the option to crossover to treatment with ribociclib + letrozole

Interventions: intervention 1: Ribociclib intervention 2: Letrozole intervention 3: Placebo
Intervention descriptions: intervention 1: Ribociclib (600 mg, in three 200 mg hard gelatin capsules or tablets) was administered orally once daily on Days 1-21 of each 28-day cycle. intervention 2: Letrozole (2.5 mg, tablets) was administered orally once daily on a continuous daily schedule (days 1-28 of each 28-day cycle) intervention 3: Placebo (hard gelatin capsules or tablets) was administered orally once daily on Days 1-21 of each 28-day cycle.

Protocol document: