Incidence, predictors and impact of positive bony margins in surgically treated T4 stage cancers of the oral cavity

Abstract

Objectives: A sea of literature addressing the adequacy of mucosal/soft tissue surgical margins in oral cavity cancers is available, but no mention exists regarding bony margins. We aim to study the predictors and impact on survival of positive bony margins and propose a safe margin distance.

Methods: This is a retrospective study of 400 consecutive surgically treated pT4 oral cavity squamous cell carcinoma patients between January 2012 and December 2015. The factors predicting positive bony margins were determined using chi-square test. Kaplan Meier and Cox regression hazard models were used for survival analysis. The median follow up was 36 months.

Results: The only factor that significantly predicted positive bony margins was lymphovascular emboli. The 3-year OS with bony margin positivity was 36.9%, compared to 67.5% for patients with adequate margins. When the tumor infiltrated the bone beyond mucosa (20.25%) the survival outcomes were significantly worse than the other patterns. Microscopic spread was seen in 10% cases, at a distance of 8 mm, the presence of which significantly impacted survival outcomes. Analysis of the receiver operating curve identified a cutoff of more than 15 mm as appropriate for classifying adequate bony margins. When the margins were taken above this, a significant positive impact on survival outcomes was present.

Conclusion: The presence of lymphovascular emboli may impact the status of bony margins. Based on our results, to achieve an "adequate margin in bone" we propose taking the bony cut at least 15 mm away from the clinically discernible tumor when treating advanced oral cancers.

Keywords: Adequate bone margins; Advanced oral cancer; Margin predictors; Positive bone margins; Safe bone margins.