Circulating low density neutrophils are associated with resistance to anti-PD1 immunotherapy in squamous head and neck cancer.

BACKGROUND: Identification of predictive biomarkers to Immune checkpoint inhibitors (ICIs) in head and neck cancer (HNSCC) is an unmet need. METHODS: This was a prospective observational study including 25 patients with HNSCC treated with immunotherapy or chemotherapy after a prior platinum-based regimen. Low density neutrophils (LDNs) and serum markers were analyzed. RESULTS: In the immunotherapy cohort, patients with high LDN levels had a shorter progression free survival (PFS) (1.8 months vs. 10.9 months; *p = 0.034). Also, progressors showed higher percentage of LDNs compared to non-progressors although significance was not reached (mean 20.68% vs. 4.095%, p = 0.0875). These findings were not replicated in patients treated with chemotherapy. High levels of interleukin-7 (IL7) were correlated with a significantly longer overall survival (OS) (13.47 months 3.51 vs. months, *p = 0.013). CONCLUSIONS: High baseline circulating LDNs and low IL7 could identify a subset of patients intrinsically refractory to ICIs as monotherapy in HNSCC.