Should sub-millimeter margins be deemed positive in oral cavity squamous cell carcinoma?

Background: While several studies have indicated that a margin status of < 1 mm should be classified as a positive margin in oral cavity squamous cell carcinoma (OCSCC), there is a lack of extensive cohort studies comparing the clinical outcomes between patients with positive margins and margins < 1 mm. Methods: Between 2011 and 2020, we identified 18,416 Taiwanese OCSCC patients who underwent tumor resection and neck dissection. Of these, 311 had margins < 1 mm and 1013 had positive margins. To compare patients with margins < 1 mm and those with positive margins, a propensity score (PS)-matched analysis (n = 253 in each group) was conducted. Results: The group with margins < 1 mm displayed a notably higher prevalence of several variables: 1) tongue subsite, 2) younger age, 3) smaller depth of invasion), 4) early tumor stage, and 5) treatment with surgery alone. Patients with margins < 1 mm demonstrated significantly better disease-specific survival (DSS) and overall survival (OS) rates compared to those with positive margins (74 % versus 53 %, 65 % versus 43 %, both p < 0.0001). Multivariable analysis further confirmed that positive margins were an independent predictor of worse 5-year DSS (hazard ratio [HR] = 1.38, p = 0.0103) and OS (HR = 1.28, p = 0.0222). In the PS-matched cohort, the 5-year outcomes for patients with margins < 1 mm compared to positive margins were as follows: DSS, 71 % versus 59 %, respectively (p = 0.0127) and OS, 60 % versus 48 %, respectively (p = 0.0398). Conclusions: OCSCC patients with a margin status < 1 mm exhibited distinct clinicopathological characteristics and a more favorable prognosis compared to those with positive resection margins.