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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.
Oral Diseases
|August 13, 2026
Summary
The margin-to-depth-of-invasion ratio offers a proportional assessment of surgical adequacy in oral squamous cell carcinoma. A ratio below 0.5 indicates higher recurrence risk and identifies patients who may benefit from postoperative radiotherapy.
Area of Science:
- Oncology
- Surgical Pathology
- Cancer Prognostics
Background:
- Surgical margin status and depth of invasion are key prognostic factors in oral squamous cell carcinoma (OSCC).
- Current definitions of adequate surgical margins are absolute (e.g., 5mm) and do not account for tumor depth.
- This fixed threshold may not accurately reflect risk for tumors with varying invasion depths.
Purpose of the Study:
- To evaluate the margin-to-depth-of-invasion (MDI) ratio as a proportional measure of surgical margin adequacy in OSCC.
- To determine if the MDI ratio can better predict local recurrence and survival outcomes compared to absolute margin distance.
- To identify if the MDI ratio can guide decisions regarding adjuvant therapy, such as postoperative radiotherapy.
Main Methods:
- Synthesized data from two retrospective studies: a 911-patient early-stage OSCC cohort and a 7420-patient node-negative OSCC registry cohort.
- Stratified patients based on absolute margin distance and the MDI ratio (defined as closest margin divided by depth of invasion).
- Analyzed the association between MDI ratio (0.5) and outcomes including local recurrence, disease-free survival, and response to radiotherapy.
Main Results:
- An MDI ratio below 0.5 was associated with significantly higher local recurrence rates (OR 2.81) in patients with non-positive margins.
- Five-year disease-free survival rates were 80.8% (clear margins), 76.3% (close margins, ratio >=0.5), and 65.2% (close margins, ratio <0.5).
- Patients with an MDI ratio >=0.5 demonstrated superior survival irrespective of absolute margin distance; radiotherapy improved survival only when the MDI ratio was <0.5.
Conclusions:
- The MDI ratio provides a tumor-proportional assessment of margin adequacy, reframing it from an absolute to a relative measure.
- An MDI ratio of 0.5 serves as a critical threshold, distinguishing high-risk from low-risk margins in OSCC.
- This ratio can identify OSCC patients who are candidates for intensified treatment, such as postoperative radiotherapy, to improve outcomes.
