It is well established that inflammation is one of the « hallmarks of cancer » that can contribute to tumour progression. It also now appears that its systemic manifestations can provide a valuable biomarker for prognosis and treatment stratification. This collection of papers illustrates how a simple indicator of systemic inflammation – based on neutrophilia and/or lymphocytopenia – can provide prognostic information in a wide range of cancer types, and in particular shows the value of one index (the dNLR), derived just from total white cell and neutrophil counts, which is enabling large retrospective studies to be carried out. Although not informative from a biological standpoint in distinguishing cause from effect, the results of these studies are likely to be of significant clinical utility.