Study for Women and Men With Hormone-receptor Positive Locally Advanced or Metastatic Breast Cancer

Inclusion Criteria

• Patient is an adult, ≥ 18 years old at the time of informed consent and has signed informed consent before any trial related activities and according to local guidelines
• Women and men with advanced (locoregionally recurrent or metastatic) breast cancer not amenable to curative therapy.
• Patient has a histologically and/or cytologically confirmed diagnosis of estrogen-receptor positive and/or progesterone receptor positive and HER2-negative breast cancer by local laboratory. Local pathology is sufficient for assessment.
• Patient must have either:
• Measurable disease, i.e., at least one measurable lesion as per RECIST 1.1 criteria ).
• Bone lesions: lytic or mixed (lytic + sclerotic) in the absence of measurable disease
• Non-measurable disease
• Patient has an Eastern Cooperative Oncology Group (ECOG) performance status ≤2

Exclusion Criteria

• Patient who received any CDK4/6 inhibitor or any mTOR inhibitor.
• Patient has a known hypersensitivity to any of the excipients of ribociclib or letrozole
• Patients with current inflammatory breast cancer.
• Patient has received > 1 chemotherapy for the treatment of advanced/metastatic breast cancer
• Patient has received > 2 endocrine therapies for the treatment of advanced/metastatic breast cancer
• Patient has central nervous system (CNS) involvement. If patient is fulfilling the following 3 criteria she/he is eligible for the trial.
• completed prior therapy (including radiation and/or surgery) for CNS metastases ≥ 28 days prior to the start of study and
• CNS tumor is clinically stable at the time of screening and
• Patient is not receiving steroids and enzyme inducing anti-epileptic medications for brain metastases
• Patient has active cardiac disease or a history of cardiac dysfunction