Margin to Depth of Invasion Ratio: A Significant Predictor of Survival in Patients With Oral Cancer

PURPOSE: A common definition of a clear margin (≥5 mm) in oral squamous cell carcinoma (OSCC) for all stages is a subject of controversy. Studies have shown that even 1- and 2-mm margins are adequate, and few studies have identified dynamic resection margin as a criterion. We aimed to study the margin to depth of invasion ratio (MDR), margin to tumor thickness ratio (MTR), and margin to tumor size ratio (MSR) as prognostic markers for survival. Notably, to our knowledge, this is the first study to evaluate the role of MDR in OSCC. METHODS: A prospectively maintained head and neck cancer database was analyzed from January 2017 to February 2023. The MDR, MTR, and MSR were calculated for each patient. Survival outcomes were analyzed using the Cox proportional model and the Kaplan-Meier method. Akaike's information criterion (AIC) and Bayesian information criterion (BIC) were used to compare different ratio models. X-tiles software was used to identify the optimal cutoff value of MDR. RESULTS: Two hundred eighty patients in the database were assessed, of which 123 eligible patients were enrolled in the study. MDR was an independent predictor of disease-free survival (DFS) on multivariate analysis. The MDR model had the lowest values on AIC and BIC analyses. A cutoff value of 0.5 for MDR showed a significant correlation with DFS and overall survival. CONCLUSION: MDR was the best predictor of recurrence of all the three ratios studied. The minimum safe surgical margin can be calculated by multiplying the depth of invasion by 0.5. This study signifies the role of dynamic resection margin criteria on the basis of MDR in defining clear margins.