1. Women of 18 years of age with proven diagnosis of advanced adenocarcinoma of the
breast (locoregionally recurrent or metastatic disease).
2. ER+ and/or PgR+ tumor based on local laboratory results :test as per local practice
3. HER2- breast cancer based on local laboratory results :test as per local practice or
4. Patients must be appropriate candidates for hormone therapy.
5. Evidence of a personally signed and dated informed consent document indicating that
the patient or a legally acceptable representative has been informed of all pertinent
aspects of the study.
1. Any patients who does not agree that Pfizer and companies working with Pfizer use
2. Known hypersensitivity to letrozole or its excipients or to any CDK4/6 inhibitor
3. Pregnant women