the effect of proton pump inhibitors on metastatic breast cancer in patients treated with cdk4/6i

Background: this study aimed to assess the effect of proton pump inhibitors (ppis) on hormone receptor-positive (hr+) and her-2-negative (her2-) metastatic breast cancer (mbc) in patients receiving cdk4/6i.method: in a retrospective study, patients were divided into two groups based on their use of ppis: concomitant use for at least half the treatment period (c-ppis) and non-concomitant use for less than half the treatment period (nc-ppis). statistical analyses were conducted using spss 22.0 and medcalc software bvba 13.results: out of 217 patients, 114 (52.5%) received palbociclib and 103 (47.5%) received ribociclib. then, 71 palbociclib recipients were combined with aromatase inhibitors (ais) (43 c-ppis and 28 nc-ppis), while 43 were combined with fulvastrant (25 c-ppis and 18 nc-ppis). for ribociclib, 82 patients were combined with ais (71 c-ppis and 11 nc-ppis) and 21 were combined with fulvastrant (10 c-ppis and 11 nc-ppis). patients with c-ppi had lower progression-free survival (pfs) than those without c-ppi, palbociclib recipients with ais or fulvastrant (8.97 months vs. 19.02 months, p < 0.001; 13.72 months vs. 18.52 months, p = 0.04, respectively) and ribociclib recipients with ais (10.7 months vs. 19.7 months, p = 0.05), but not in patients who received ribociclib with fulvastrant (p = 0.52).conclusion: the simultaneous use of ppis with palbociclib or ribociclib may be associated with a shorter pfs in hr+, her2- mbc patients. these results have the potential to enhance clinical decision-making by identifying possible drug interactions and optimizing treatment plans.