Elevated serum interleukin-8 is associated with enhanced intratumor neutrophils and reduced clinical benefit of immune-checkpoint inhibitors.

Serum interleukin-8 (IL-8) levels and tumor neutrophil infiltration are associated with worse prognosis in advanced cancers. Here, using a large-scale retrospective analysis, we show that elevated baseline serum IL-8 levels are associated with poor outcome in patients (n = 1,344) with advanced cancers treated with nivolumab and/or ipilimumab, everolimus or docetaxel in phase 3 clinical trials, revealing the importance of assessing serum IL-8 levels in identifying unfavorable tumor immunobiology and as an independent biomarker in patients receiving immune-checkpoint inhibitors. In a retrospective analysis of data from four phase 3 clinical trials, elevated baseline serum IL-8 levels were associated with worse clinical outcomes in patients with multiple tumor types treated with anti-PD-1 monotherapy or anti-PD-1 and anti-CTLA-4 combinatorial therapy.