Correlations of 18F-FDG PET/CT metabolic parameters and systemic immune-inflammation index with distant metastasis of small-size (T1) NSCLC

Background: F-FDG) positron emission tomography/computed tomography (PET/CT) metabolic parameters and the systemic immune-inflammation index (SII) are linked to NSCLC progression, but their associations with distant metastasis in small-size NSCLC remain unclear. This study aimed to investigate these correlations to identify reliable metastatic risk factors for small-size NSCLC. Methods: F-FDG PET/CT within two weeks before tumor resection or biopsy. PET/CT metabolic parameters including standardized uptake value peak (SUVpeak), standardized uptake value maximum (SUVmax), standardized uptake value mean (SUVmean), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and coefficient of variation (COV) at various SUV thresholds (1.0, 1.5, 2.0, and 2.5) were assessed for primary lesions. Inflammation factors including SII were measured one day prior to surgery or biopsy. Patients were randomized into modeling (n=182) and validation (n=61) cohorts (3:1). Univariate/multivariate logistic regression analyses identified independent risk factors for metastasis correlations between metabolic parameters and serum inflammation markers were analyzed. Results: In the modeling cohort, high SUVpeak, SUVmean, SUVmax, MTV, TLG, and COV were significantly associated with distant metastasis (all P0.33 as an independent risk factor [hazard ratio (HR) =3.03, P=0.01]. SII >641.68 was also identified as an independent inflammation-related risk factor (HR =2.84, P=0.003). COV2.0 was positively correlated with SII [odds ratio (OR) =4.55, P=0.03]. The co-high COV2.0/SII status was identified as an independent risk factor for metastasis (HR =5.08, P