Proton pump inhibitors and antibiotics adversely effect the efficacy of nivolumab in patients with recurrent or metastatic squamous cell carcinoma of the head and neck

Background Several reports have shown that the use of proton pump inhibitors (PPIs) and antibiotics (Abx) can reduce the efficacy of immune checkpoint inhibitors in various cancers. To date, however, the association of immune checkpoint inhibitors with PPI and/or Abx in patients with recurrent or metastatic head and neck squamous cell carcinoma (R/M SCCHN) has not been reported. Methods We retrospectively reviewed patients with platinum-refractory R/M SCCHN treated with nivolumab from May 2017 and March 2020 in our institute. Primary sites included the oral cavity, oropharynx, hypopharynx and larynx. The relationship between prognostic parameters, such as overall survival (OS), progression-free survival (PFS), PFS2 and PFS3, and clinical factors, including PPI or Abx use, was examined, and the creation of prognostic classification was also attempted. Results Of 110 patients identified, 56 patients received PPI and 24 patients received Abx within 30 days before or after the initiation of nivolumab. With a median follow-up of 17.2 months (range: 13.8–25.0), median PFS, PFS2, PFS3 and OS were 3.2, 8.1, 14.0 and 17.2 months, respectively. In univariate analysis, the use of PPI and of Abx was significantly associated with poor prognosis in all parameters (PFS, PFS2, PFS3 and OS). Median OS (hazard ratio; 95%confidence interval, p-value) by these covariates were 13.6 versus 23.8 months (1.70; 1.01–2.87, p = 0.046) for PPI and 10.0 versus 20.1 months (1.85; 1.00–3.41, p = 0.048) for Abx, respectively. Furthermore, these factors showed mutually independent adverse associations on multivariate analysis. Conclusion The use of PPI and Abx attenuated the efficacy of nivolumab in R/M SCCHN. Further prospective evaluation is warranted.