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William J. Gradishar, MD, FACP, FASCO


Do Proton Pump Inhibitors Reduce the Efficacy of Palbociclib in Patients With Breast Cancer?

By: Chris Schimpf, BS
Posted: Friday, August 11, 2023

Proton pump inhibitors may inhibit the therapeutic effects of the CDK4/6 inhibitor palbociclib in patients with breast cancer, according to research published in JAMA Network Open. In a South Korean retrospective cohort study, Eui-Kyung Lee, PhD, of Sungkyunkwan University, Gyeonggi-do, and colleagues observed considerably reduced progression-free survival and overall survival among patients taking palbociclib who also took proton pump inhibitors compared with those who did not. The investigators urged caution on the part of physicians when prescribing these gastrointestinal medications to patients taking palbociclib, and they recommended informing patients of the risks of interactions between the two.

“To our knowledge, insufficient data and small sample size have limited retrospective studies reporting drug-drug interactions between proton pump inhibitors and palbociclib,” the researchers noted. “In this study, we aimed to identify the clinical outcomes of patients with hormone receptor–positive and ERBB2-negative advanced or metastatic breast cancer who concomitantly use [both].”

The study used nationwide South Korean insurance claims data to identify patients who received palbociclib between November 2017 and July 2020. Patients whose prescriptions for palbociclib and proton pump inhibitors overlapped by at least 33% were classified into a concomitant group, and patients who never received proton pump inhibitors during treatment with palbociclib were classified into a nonconcomitant group.

A total of 344 women were included in the concomitant group versus 966 women in the nonconcomitant group. The median clinical progression-free survival was 25.3 months (95% confidence interval [CI] = 19.6–33.0 months) versus 39.8 months (95% confidence interval [CI] = 34.9 months to not applicable), respectively, and the hazard ratio [HR] was 1.76 (95% CI = 1.46–2.13). Proton pump inhibitors were also associated with shorter overall survival (HR = 2.71; 95% CI = 2.07–3.53). Both clinical progression-free survival and overall survival in the concomitant group were consistently poor in patients receiving endocrine-sensitive and endocrine-resistant treatment, according to the investigators.

Disclosure: The study authors reported no conflicts of interest.

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