An excessive weight loss percentage over the two years before treatment is an independent prognostic factor for operated patients with advanced oral squamous cell carcinoma.

The aim of this study was to assess the prognostic value of the weight loss percentage (WLP) over the 2 years pre-treatment for operated patients with advanced oral squamous cell carcinoma (OSCC). This cohort study included 506 operated patients who were diagnosed with advanced primary OSCC between October 2001 and March 2022, and who were followed up until July 2022. Fine-Gray models, marginal structural models with stabilized inverse probability of treatment weighting, and Cox proportional hazards models were utilized to evaluate the prognostic significance of pre-treatment WLP for disease-specific survival (DSS). The median follow-up time was 32.6 months (interquartile range 13.0-71.6 months). A high pre-treatment WLP (>9.23%) was significantly associated with worse DSS (multivariate Fine-Gray model: hazard ratio (HR) 2.04, 95% confidence interval (CI) 1.29-3.22, P = 0.002; multivariate Cox: HR 2.01, 95% CI 1.28-3.16, P = 0.002). In the weighted cohort, a similar association pattern was observed (marginal structural model: HR 2.26, 95% CI 1.28-3.98, P = 0.005; multivariate Cox: HR 2.28, 95% CI 1.38-3.76, P = 0.001). In subgroup analyses, high WLP could predict worse DSS among patients with buccal mucosa/other cancer sites (not including the oral tongue), moderate tumor differentiation, and larger cancer size (>1.8 cm) (all P < 0.05). Pre-treatment WLP over 2 years might be a useful tool to predict the prognosis of operated patients with advanced OSCC.