Mandibular bone invasion by gingival carcinoma on dental CT images as an indicator of cervical lymph node metastasis.

OBJECTIVES

To evaluate the significance of mandibular bone invasion by gingival carcinoma revealed by reformatted dental CT images as a prognostic indicator of cervical metastasis.

METHODS

Thirty-two patients with squamous cell carcinoma of the lower gingiva were examined by dental CT. Cervical metastases and survival rates of these patients were analysed in relation to their clinical characteristics, histologic grading based on gingival biopsy, and mandibular bone invasion using reformatted dental CT imaging diagnoses prior to surgery. The dental CT images were classified into four types: Class I, no bone invasion; Class II, invasion confined to the alveolus; Class III, invasion extending between the alveolus and the mandibular canal; and Class IV, invasion beyond the mandibular canal.

RESULTS

Logistic multivariate regression analysis showed that bony invasion identified on dental CT images was a significant prognostic factor in cervical metastases (P=0.028). The 5-year overall survival rates of Classes I, II, III, and IV were 100% (n=9), 76.2% (n=9), 71.4% (n=7), and 28.6% (n=7), respectively.

CONCLUSIONS

The evaluation of mandibular bone invasion using dental CT images is useful as a prognostic indicator of cervical metastasis for patients with gingival carcinoma.