The purpose of this study is to evaluate the efficacy and safety of Letrozole SIE (injectable) compared to Femara® (oral tablet), both given together with ribociclib, for the first-line treatment of postmenopausal women with HR-positive, HER2-negative, inoperable locally advanced or metastatic breast cancer.
Female participants with inoperable locally advanced or metastatic breast cancer.
Confirmed diagnosis of HR-positive/HER2-negative breast cancer.
Postmenopausal woman.
Previously untreated with any systemic anticancer therapy for their locoregionally recurrent or metastatic HR-positive disease. Participants may have received cytotoxic chemotherapy within (neo) adjuvant previous treatment of breast cancer but must show progressive disease prior to enrollment.
Participants with advanced, symptomatic, visceral spread who are at risk of life-threatening complications in the short term.
Participants with inflammatory breast cancer.
Known uncontrolled or symptomatic central nervous system (CNS) metastases.
Concurrent malignancy or malignancy within 3 years of randomization, with the exception of adequately treated basal or squamous cell carcinoma, non-melanomatous skin cancer, or curatively resected cervical cancer.