The clinical relevance of the interaction between human cancer and neutrophils has recently begun to emerge. This review will focus on recently published articles regarding immunomonitoring of neutrophils in blood and tumor tissue in clinical trials comprising the main human tumor types, with a strong emphasis on independent prognostic relevance assessed by multivariate analyses. The prognostic role of tumor-infiltrating neutrophils, elevated blood neutrophils and elevated blood neutrophil/lymphocyte ratio has been associated with poor clinical outcome in several human cancers, most notably in renal cell carcinoma, melanoma, colorectal cancer, hepatocellular carcinoma, cholangiocarcinoma, glioblastoma, GIST, gastric, esophageal, lung, ovarian and head and neck cancer. A striking finding is the notion that high baseline neutrophil count in either tumor or blood, or both, was identified as strong, independent risk factor for poor outcome in multivariate analyses, and the negative prognostic impact of neutrophils was not eliminated by increasing the dose of cytokines, chemotherapy, or targeted therapy. For several cancers, patients benefit most from therapy if baseline neutrophil was low. Thus, baseline neutrophils over-ride nadir counts in prognostic significance. In summary, a proportion of patients who do not experience benefit from surgery or medical intervention may be associated with a worst prognosis because they are characterized by baseline tumor-related neutrophilia protecting them from benefit from therapy. Further research to unraveling the cancer biology and new treatment options is encouraged.
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