Association between proton pump inhibitors and severe hematological toxicity in patients receiving pemetrexed-based anticancer treatment: The prospective IPPEM study.

OBJECTIVE: Pemetrexed is associated with hematological toxicity. Drug-drug interactions (DDIs) between methotrexate and proton pump inhibitors (PPIs) induce a higher risk of hematological toxicity due to the inhibition of methotrexate excretion by PPIs. As pemetrexed and methotrexate are both excreted by human organic anion transporter 3 (hOAT3), this study investigates the hypothetical DDI between pemetrexed and PPIs in lung cancer patients. The primary objective was the occurrence of severe (grade ≥ 3) hematological toxicity. The secondary objectives were to describe the type of hematological toxicity and associated clinical consequences (NCT03537833). MATERIALS AND METHODS: PPI consumption was collected for each patient receiving pemetrexed-based anticancer chemotherapy from May 2018 to October 2020 in a prospective multicentric observational and nonrandomized study. Multivariate Cox regression and propensity score (PS) adjustment, PS matching and inverse weighting on PS (IPTW) methods were used. RESULTS: PPI consumption (55 among 156 included patients) was associated with a significantly higher risk of severe hematological toxicity in the multivariable Cox regression model (hazard ratio HR = 2.51, 95% confidence interval [1.47-4.26]; p = 0.005). Similar results were found with PS adjustment (HR = 1.91 CI95% [1.14-3.20]; p = 0.002), PS-matching (HR = 1.93 CI95% [1.08-3.45]; p = 0.02) and IPTW method (HR = 2.06 CI95% [1.27-3.35]; p = 0.004). Severe neutropenia and anemia occurred in 32.7% and 14.1% of patients, respectively. This resulted in 48 anticancer chemotherapy postponements and 24 dose adjustments, 26 growth factor prescriptions, 24 red blood cell transfusions, and 20 hospitalizations. CONCLUSIONS: The results strongly suggest an association between PPI consumption and pemetrexed-related severe hematological toxicity. Deprescription of PPIs when feasible should be considered to prevent this DDI.