Effect of Concurrent Proton Pump Inhibitors With Palbociclib Tablets for Metastatic Breast Cancer.

BACKGROUND:Palbociclib is indicated for the treatment of hormone receptor positive (HR+) human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer (MBC) in combination with an aromatase inhibitor or fulvestrant. Two retrospective studies found that concurrent proton pump inhibitor (PPI) use with palbociclib capsules significantly reduced progression free survival (PFS) versus patients without a PPI. Palbociclib tablets were released in 2020 without restriction on PPI use. No study to date has evaluated the combination of palbociclib tablets with concurrent PPI use. METHODS:Patients were retrospectively evaluated after they received palbociclib tablets for the treatment of HR+ HER2- MBC in the first line setting with or without a PPI. Patients were assigned to the no PPI use arm if they never used a PPI and the PPI use arm if they used a PPI for >50% of the duration of palbocicib therapy. The primary endpoint was PFS. The secondary endpoints included overall survival (OS) and adverse events. RESULTS:Eighty-two patients were identified; 50 in the no PPI use group and 32 in the PPI use group. The median PFS was 20.6 months (95% confidence interval [CI], 16.07 to not estimable) in the no PPI use arm versus 21.0 months (95% CI, 15.15 to not estimable) in the PPI use arm (P = 0.95). Median OS was not reached in either arm. Adverse effects did not differ between arms. CONCLUSION:Use of a concurrent PPI with palbociclib tablets does not significantly reduce PFS in patients treated for HR+ HER2- MBC.