Abstract
The Japanese Society of Oral Oncology held its first workshop in 1993 on the T classification of lower gingival carcinomas, where 12 proposals were presented. We could not come to a conclusion and agreed to conduct further studies and collect many cases from nationwide surveys. There were 1,187 registered cases which were statistically analyzed by applying 12 proposals for the T classification in terms of T. The stage distribution, survival rate, factor analysis, mathematical quantification method II, partial correlation coefficient with surgical methods used for the primary site, multiple correlation coefficient with prognosis, and the level of mandibular canal (LMC) criteria were found to be the most appropriate criteria for the T classification of lower gingival carcinomas. Then, the local recurrence rate after surgical treatments in the registered cases was analyzed and the desirable mode of mandibulectomy by using LMC criteria, bone invasion level and bone invasion pattern to minimize local recurrence was analyzed by logistic regression analysis and proposed. The concept of LMC criteria and the proposed mode of mandibulectomy in the surgical treatment of lower gingival carcinomas have been adopted in the clinical practice guideline for oral cancer by the JSOT and JSOMS and in the general rules for clinical and pathological studies on oral cancer by the JSOT.
