Evaluation of the Systemic Immune-Inflammation Index, Neutrophil-to-Lymphocyte Ratio, and Platelet-to-Lymphocyte Ratio in Patients Diagnosed with Lung Cancer by Bronchoscopy in Relation to Disease Stage and PET/CT SUVmax

Abstract

Systemic inflammation in lung cancer is closely associated with tumor progression and prognosis. Hematological parameters such as the systemic immune-inflammation index (SII), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) are readily available, low-cost biomarkers. This study aimed to evaluate the associations of SII, NLR, and PLR with disease stage and the maximum standardized uptake value (SUVmax) measured by 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in patients with lung cancer diagnosed by bronchoscopy.

This retrospective study included 184 of 357 patients who underwent fiberoptic bronchoscopy at the Department of Respiratory Medicine, Kütahya Health Sciences University, between January 2023 and March 2025 and had complete staging data. Demographic characteristics, histopathological diagnoses, 18F-FDG PET/CT SUVmax values, and SII, NLR, and PLR values calculated from complete blood count parameters were recorded.

A total of 184 patients were included; 172 (93.5%) were male and 12 (6.5%) were female, and the mean age was 67.9 ± 8.4 years. The most common histopathological diagnosis was non-small cell lung cancer (NSCLC), accounting for 84.8% of cases. No significant associations were found between SII, NLR, or PLR and disease stage or SUVmax. NLR showed a statistically significant but very weak positive correlation with stage IV NSCLC (r = 0.198, p = 0.013), indicating limited explanatory value.

The inflammatory indices were not significantly associated with disease stage or 18F-FDG PET/CT SUVmax. Although NLR showed a statistically significant positive correlation with stage IV NSCLC, the effect size was very small and should not be interpreted as evidence of meaningful staging utility. Larger prospective studies are needed to determine whether readily available hematological indices such as SII, NLR, and PLR provide complementary value in prognostic or multimarker models in lung cancer.