Real-world palbociclib dosing patterns and potential wastage associated with dose modifications among post-menopausal women with HR-positive/HER2-negative metastatic breast cancer (mBC).

17Background: CDK4/6 inhibitor palbociclib is recently approved for the treatment of HR+/HER2- mBC and its treatment patterns have not been thoroughly understood. This study described real-world palbociclib dosing patterns in the US. Methods: Postmenopausal women with HR+/HER2- mBC who initiated palbociclib-based therapy (date of initiation was defined as index date) between 02/03/2015 (palbociclib approval date) and 02/29/2016 (end of data) were identified from Symphony Source Lx database. Patients were required to have continuous quarterly medical/pharmacy activity for 1 year prior to and 6 months after the index date. Dose decrease or increase (collectively, dose modification) was defined as a change of daily dose of >=25 mg compared to the last dose. Dose interruption was defined as a treatment gap within 60 days before restarting the treatment as the last dose. Kaplan-Meier analyses were conducted to assess dose decrease rate and dose decrease/interruption rate within one year from the index date. Th...