Proton pump inhibitors and response to immune check-point inhibitors: Single center study.

e14092 Background: Checkpoint inhibitors (blocking antibodies to PD-1, PD-L1, CTLA-4) have proven effective against several tumor types. While the response is impressive in some patients, we still don’t understand all the patient factors that determine resistance to this class of medication. Studies of host factors have identified composition of the gut microbiome at baseline as a positive predictor of ICI response. Proton pump inhibitors have been reported to interfere with gut microbiome composition. In this single center, retrospective study, we studied the effect of concomitant treatment of proton pump inhibitors on response to ICIs in patients with locally advanced and metastatic cancer. Methods: A retrospective cohort of Non-small cell lung cancer, renal cell carcinoma and Melanoma patients that were treated from January 2016 to May 2018 at the Mount Sinai Medical Center were included in this study. Demographics, prior systemic treatment, performance status, ICI agent, and use of PPI (with in 30 days prior to 30 days after the first dose of ICI administration) were collected. Primary objective of the study was progression free survival (PFS) by utilization of PPIs. PFS was calculated using the log-rank test and survival curve was generated using the Kaplan-Meier method. Information was collected from electronic medical records. Results: Of the 97 patients that met the study criteria, 63 patients had complete data and included in the analysis. 46 patients had Non-small cell lung cancer, 13 had melanoma and 4 renal cancer. Checkpoint inhibitors most commonly prescribed included: Pembrolizumab (29 patients : 46%), Nivolumab (22 patients:35%), Nivolumab + Ipilimumab (9:14 %). 25 patients were taking PPI upon initiation of ICI treatment. In addition, 26 patients received steroids with in 30 days of treatment initiation. There was no statistically significant difference in PFS between patients on PPIs and not on PPIs. The median PFS was 672 days (95% CI: 32, 1311) for PPI users and 341 days (95% CI: 123, 558) for non PPI users. P = 0.244. Conclusions: In this, single-center, retrospective study, we did not detect a significant difference in PFS between patients who used PPI at baseline and patients who did not. Limitations of this study mainly included retrospective analysis, a small sample size, single center population and heterogeneity in disease pathology. We did not collect information on other tumor and treatment related factors like PDL 1 expression, tumor mutation burden, use of antibiotics, and immunotherapy related adverse reactions.