The incorporation of depth of invasion (DOI) into the AJCC 8th edition staging system substantially changed risk stratification in oral squamous cell carcinoma (OSCC), with important implications for adjuvant treatment decision-making. This retrospective cohort study was performed to evaluate the impact of adjuvant treatment on the risk of recurrence and mortality in patients with OSCC and DOI >1 cm. Overall, 818 consecutive patients treated surgically for OSCC were included. All possible two-factor interactions (treatment and adverse features) were tested using multivariate models. Patients with OSCC and DOI >1 cm who did not receive postoperative radiotherapy (PORT) had significantly worse disease-specific survival (hazard ratio 4.55, 95% confidence interval 2.89-7.16; P 1 cm treated with PORT, the excess risk was attenuated (hazard ratio 1.45, 95% confidence interval 1.03-2.05; P = 0.033), with consistent patterns across disease-free survival, loco-regional recurrence-free survival, and overall survival. Significant interaction effects with radiotherapy were also identified for selected high-risk features, including perineural invasion, pT4a/b status, and nodal positivity; no significant interaction was observed for surgical margins or extranodal extension. For concurrent chemotherapy, significant interaction effects were mainly observed for pT4a/b and pN positivity. This study is novel in recognizing the imperative need for PORT in OSCC with DOI >1 cm, independently of other well-established prognostic factors or those deemed high risk for these patients.
Matos et al. (Mon,) studied this question.