Study of Efficacy and Safety of LEE011 in Men and Postmenopausal Women With Advanced Breast Cancer.

This study was a randomized, phase III, double-blind, placebo-controlled international trial aimed at determining the efficacy and safety of treatment with fulvestrant in combination with ribociclib compared to fulvestrant with placebo in men and postmenopausal women diagnosed with HR+, HER2-negative advanced breast cancer. The study comprised four phases: screening (up to 28 days), randomized treatment, post-treatment disease progression follow-up, and post-treatment survival follow-up. Enrolled participants were randomly assigned to receive either fulvestrant+ribociclib or fulvestrant+placebo in a ratio of 2:1. The randomization process was stratified based on the presence of liver and/or lung metastases (yes versus no) and prior endocrine therapy. Treatment was administered until disease progression, occurrence of unacceptable toxicity, or discontinuation from the study treatment for other reasons. 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. All participants who discontinued treatment were followed for survival until the predetermined number of overall survival (OS) events was reached. A protocol amendment 4 (dated 29-Jan-2020) allowed for unblinding of study participants, and those still receiving placebo had the option to switch to the ribociclib arm. The decision for crossover was made at the investigator's discretion and required patient consent.