Study to Evaluate Real-world Effectiveness With Palbociclib Plus Endocrine Therapy as First-line/Second-line Treatment for HR+/HER2- Advanced Breast Cancer in Japan

Inclusion Criteria

• •Diagnosis of HR+/HER2- ABC
• •Age of 20 years or older at diagnosis of ABC
• •Patients that received palbociclib plus ET in the first line or second line
• •Patients who meet the criteria regarding the medical record below:
• •Patients with any medical records (regardless of palbociclib use) for more than 6 months from palbociclib initiation OR
• •Patients with any medical records for less than 6 months from palbociclib initiation AND who had specific events (death, disease progression, or treatment discontinuation of palbociclib due to adverse events) in the available records