Impact of 3mm margin on risk of recurrence and survival in oral cancer.

Abstract

While positive surgical margins in oral squamous cell carcinoma (OSCC) is generally considered an adverse prognosticator, the significance of close (≤5 mm) margins is more debatable, and has not been widely adopted as an indicator for radiotherapy. Retrospective study of 244 patients undergoing primary surgical resection of OSCC. The impact on local control (LC), disease-specific survival (DSS) and overall survival (OS) of margins at 1mm intervals was studied. 65 patients had involved (<1 mm), 119 close (1-5mm), and 60 clear (>5 mm) main specimen margins. Involved margins was predictive of DSS (p=0.04), but not LC (p=0.20) or OS (p=0.09). Both the 2mm and 3mm margin cut-offs were significantly associated with LC (p=0.02, and p=0.01), DSS (p=0.02, and p=0.007), and OS (p=0.03. and p=0.005). In a 3-tier model, use of 3mm for demarcation between close and clear yielded good separation between survival curves of clear (≥3 mm), and close (1-<3 mm) or involved (<1 mm). Final margins, determined after incorporation of frozen sections and extra margins taken separately, was significant for LC (p=0.04), but not for DSS (p=0.05) or OS (p=0.17). On multivariate analysis, <3 mm margin, T-classification, nodal status, extranodal spread, and postoperative radiotherapy, were independent predictors of DSS and OS. For LC, only T-classification was significant. A 3mm main specimen margin is significantly associated with survival in OSCC and may be useful for demarcation between close and clear. Further study is required to determine any impact on survival of radiotherapy for patients with <3mm margins as sole indicator for radiotherapy.