Inflammation and immune surveillance evasion are cancer hallmarks. Peripheral blood leukocytes (PBLs) represent both. The aim of the current study was to examine PBLs as predictors of outcomes in oral cavity squamous cell carcinoma (OSCC), and to find specific cutoffs with the goal of including PBLs as host factor in patients' preoperative risk assessment.

Previously established head and neck squamous cell carcinoma (HNSCC) cutoffs were examined in an independent cohort of 1369 OSCC patients. Then optimal OSCC cutoffs were found and validated in the subset of patients with OSCC (n = 119) from the external HNSCC cohort. The PBLs analyzed were neutrophils, monocytes, and lymphocytes individually, the neutrophil-to-lymphocyte ratio (NLR), and a combined index using all PBLs called Systemic Inflammation Response Index (SIRI).

All parameters were significant predictors of survival using the previous cutoffs. However, OSCC cutoffs stratified survival outcomes better. Considering neutrophils ≤4.8 × 10⁹ /L as reference, patients with 4.8-9.1 × 10⁹ /L neutrophils had 1.536 times higher risk of death (95% CI, 1.295-1.822), and patients with ≥9.1 × 10⁹ /L had 3.076 times higher risk (95% CI: 2.170-4.360). All PBLs maintained independent prognostic capacity in multivariable analysis. Neutrophils, NLR, and SIRI were significant predictors of survival when validating OSCC cutoffs in the external validation cohort.

Pretreatment peripheral blood neutrophils, NLR, and SIRI are the most robust independent predictors of overall survival among all PBLs in OSCC. The authors report externally validated cutoffs that demonstrate the feasibility of including PBLs as host features in the preoperative prognostication of OSCC.