Related Experiment Video
Updated: Aug 14, 2026

Intraoperative Assessment of Resection Margins in Oral Cavity Cancer: This is the Way
Published on: May 10, 2021
Margin-To-Depth-Of-Invasion Ratio: A Paradigm Shift in Oral Cancer Margin Assessment
Chun-Yang Hung1, Li-Jen Liao2, Tseng-Cheng Chen1
1Department of Otolaryngology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
Objective:
Surgical margin status and depth of invasion are established prognostic factors in oral squamous cell carcinoma, yet an adequate margin remains undefined. A fixed 5 mm threshold is applied to tumors of widely varying depth. We examined the margin-to-depth-of-invasion ratio, the closest surgical margin divided by the depth of invasion, as a tumor-proportional alternative.
Methods:
We synthesized two retrospective studies: a single-institution cohort of 911 patients with early-stage disease, and a nationwide registry cohort of 7420 patients with node-negative disease across all tumor classifications, each stratified by margin distance and by ratio (below 0.5 versus 0.5 or greater).
Results:
A ratio below 0.5 predicted higher local recurrence among non-positive margins (odds ratio 2.81). Five-year disease-free survival was 80.8% with clear margins, 76.3% with close margins and a ratio of 0.5 or greater, and 65.2% with close margins and a ratio below 0.5. Nationwide, both subgroups with a ratio of 0.5 or greater showed superior survival regardless of margin distance. Postoperative radiotherapy improved disease-free survival only when the ratio was below 0.5.
Conclusions:
The margin-to-depth-of-invasion ratio reframes margin adequacy as proportional rather than absolute. A ratio of 0.5 distinguishes high-risk from low-risk margins and identifies candidates for postoperative radiotherapy.
