Indication adherence and outcome of post-operative radiotherapy in oral cavity cancer patients with intermediate adverse pathological tumor features: A nationwide population-based analysis

Abstract

Purpose: The significance of intermediate-risk adverse pathological features in oral squamous cell carcinoma (OSCC) remains unclear. Consequently, the indications for postoperative radiotherapy (PORT) vary between hospitals. This study evaluates treatment patterns and outcomes of PORT for OSCC patients with intermediate-risk adverse pathological features in a real-world national cohort. Materials and methods: All first primary OSCC patients (n = 683) with intermediate-risk adverse pathological features from the tumor treated between 2018 and 2021 in the Netherlands were included. Features were 1–5 mm resection margins, pT3-T4 classification, perineural invasion, worst pattern of invasion (WPOI) 4–5, or vaso-invasive growth. Odds ratios (ORs) for receiving PORT were calculated using multivariable regression analysis. Hospital variation was assessed using funnel plots. Two-year overall survival (OS) and local control (LC) were evaluated using multivariable Cox regression analysis. Results: The percentage of patients receiving PORT increased when more features were present (4.0% for 1 feature, 67% for all features). Significant predictors for PORT were pT3-T4 (OR 23.3), 1–5 mm margin (OR 3.72), WPOI 4–5 (OR 1.83) and perineural invasion (OR4.75). Patients with vaso-invasive growth (OR 0.19) and increasing age (OR 0.96) received PORT less often. Hospital differences in PORT treatment remained after correction for confounders. PORT did not significantly improve the adjusted hazard ratio for LC (1.56, p = 0.36) and OS (0.55, p = 0.08). Conclusion: Of the tumor-related pathological features, pT3-pT4 contributed the most to PORT treatment in OSCC. Significant hospital differences remained after correction for confounding factors. Future research should focus on guideline consensus to prevent over- and undertreatment.