A Study to Understand About the Study Medicine Palbociclib in Breast Cancer Patients After it is Out in the Japanese Market

Inclusion Criteria

• •Having prescription records of drugs for endocrine therapy (aromatase inhibitors, SERDs, SERMs, and CDK4/6 inhibitors) from 25 November 2011 to 31 December 2024.
• •Having any breast cancer records with definitive diagnosis in the same month as the first prescription date.
• •Having any records in MDV database on or before 6 months prior to the first prescription date (\<= -180 days: first prescription date = 0 day).
• •Having any records in MDV database within 6 months prior to the first prescription date (-180 days to 0 day).