Optimum Surgical Margins in Squamous Cell Carcinoma of the Oral Tongue: is the Current Definition Adequate?

Objectives: To evaluate the impact of progressively increasing margin distances on locoregional recurrence-free survival (LFRS) and determine an optimum margin distance for tongue cancers. Methods: We retrospectively reviewed the records of patients with squamous carcinoma of oral tongue, surgically treated between January 2012 and December 2013. The patients were divided based on ROC derived optimal distance and differences in LRFS per millimeter: margin distances with no significant difference in LRFS starting from 0 mm onwards (Group-I), from upper limit of Group-I to ROC cut-off (Group-II), and all values above it (Group-III). Group-II and III were matched for clinicopathologic factors and type of adjuvant therapy received. Results: 451 patients had a median LRFS of 29.4 months that included 32.1% of Stage I/II and 51.7% of Stage III/IV. Group-I consisted of 0--2.0 mm (2.0-2.1 mm (p-0.029)), Group-II form 2.1 to 7.5 (7.5-7.6 mm (p-0.042)) and Group-III were >= 7.6 mm. In the matched group, each millimeter increase in margin provided a 3.67 months survival advantage from 2.1 mm to 7.5 mm while a substantial advantage of 15 months was seen from 7.5 to 7.6 mm. No significant advantage was gained in LRFS when the margin was increased by a millimeter from the cut-off value (p-0.602). Among the patients that were not prescribed any adjuvant therapy, a significantly better LRFS was observed in Group III than Group II (HR-3.01,p-value = 0.002). Conclusion: Based on these results, adequacy of surgical margins should be re-considered for oral tongue cancers.