Proton pump inhibitors reduce nivolumab efficacy in unresectable advanced or recurrent gastric cancer

BACKGROUND: Proton pump inhibitors (PPI) have been shown to decrease the efficacy of immune checkpoint inhibitors in patients with various cancer types. However, there are few reports on their effect on patients with gastric cancer (GC). Therefore, we investigated the efficacy of nivolumab in patients with GC receiving PPI. METHODS: This retrospective study analyzed data of patients who received nivolumab monotherapy for unresectable advanced or recurrent GC at Osaka Metropolitan University Hospital between September 2017 and December 2021. The primary and secondary endpoints were progression-free survival (PFS) and overall survival (OS), respectively. PPI use was defined as within 30 days before and after initiation of nivolumab monotherapy. RESULTS: = 0.042). Contrastingly, PPI use was not an independent predictor of OS. CONCLUSION: PPIs may reduce the efficacy of nivolumab, and their use should be carefully considered in patients receiving nivolumab.