Potential Diagnostic and Prognostic Value of Neutrophil Counts, Neutrophil–Lymphocyte Ratio, Pan-Immunoinflammatory Score, Systemic Immunoinflammatory Index, and Systemic Inflammatory Response Index in Brain Tumors

<b>Background/Objectives</b>: The aim of this study is to investigate the possible association between systemic inflammation parameters and tumor presence in brain tumor patients with high morbidity and mortality rates, to examine the discriminative performance of these markers and, furthermore, to investigate the relationship of these markers with the clinical findings of patients at different time points. <b>Methods</b>: This study included 99 patients with brain tumors as the case group and 99 healthy individuals as the control group. Neutrophil, lymphocyte, monocyte, and platelet levels, as well as indices and ratios derived from these parameters, were compared among the participants. Binary logistic regression and ROC analyses were applied to variables showing significant differences, and the relationship between these variables and demographic and clinical findings was also evaluated. <b>Results</b>: The neutrophil count, neutrophil-lymphocyte ratio (NLR), pan-immunoinflammatory value (PIV), systemic immunoinflammatory index (SII), and systemic inflammatory response index (SIRI) values of the case group were higher compared to the control group. While these parameters were associated with the presence of brain tumors, the highest odds ratio, area under the curve, and specificity were found in the neutrophil count, and the highest sensitivity was found in the SIRI parameter. Some or all of these parameters differed according to tumor type, localization, motor weakness, 3-month adjuvant treatment, 6-month recurrence, postoperative day 1, 3-month and 6-month neurological deficits and 3-month and 6-month Karnofsky Performance Status. <b>Conclusions</b>: These parameters can be considered useful biomarkers that show moderate discrimination in patients with brain tumors and can support clinical evaluation.