Tumour immune infiltration is independent of peripheral circulation of white blood cells in glioblastoma

Glioblastomas are the most prevalent and malignant primary cancers in the brain. Given the promising prospects of immunotherapeutic approaches, there is increasing interest in obtaining precise knowledge of the immunologic status of the tumour microenvironment for each individual. We explored the feasibility of inferring this tumour immune component in a minimally invasive manner prior to any clinical intervention, taking advantage of the preoperative immune cell counts that can be easily obtained from the clinical records of the patients. The neutrophil-to-lymphocyte ratio (NLR) is the most extensive measure calculated from complete counts of peripheral blood. Despite there was an increase in the NLR in high grade tumours of our cohorts of study, we did not find evidence of any correlation between the NLR and different degrees of tumour immune infiltration in glioblastoma. The same negative result was obtained with the monocyte-to-lymphocyte ratio (MLR). In addition, glioblastomas associated with extreme values of peripheral NLR did not exhibit substantial gene expression differences that could be linked to distinct tumourigenic properties. Overall, these results suggest that peripheral immune cell ratios cannot be used to reliably infer the immune microenvironment within the tumour, underscoring the complexity of using peripheral markers to assess local tumour immunity.