Concomitant Use of Proton Pump Inhibitors and Palbociclib Among Patients With Breast Cancer.

Importance: Proton pump inhibitors (PPIs) are commonly used drugs to relieve gastrointestinal tract symptoms, but their acid-inhibitory action negatively affects the bioavailability and clinical outcomes of orally administered concomitant drugs.

Objective: To identify the clinical outcomes of patients with advanced breast cancer who concomitantly use PPIs and palbociclib.

Design, Setting, And Participants: This retrospective cohort study used nationwide claims data between November 1, 2016, and July 31, 2021, in South Korea.