Previous studies have reported variable results for the impact of bone invasion on survival in oral cancer. It is unclear whether bone invasion in small (≤4 cm) squamous cell carcinomas (SCC) of the oral cavity is an independent adverse prognosticator. Our objective was to investigate impact on survival of bone invasion in SCC of floor of mouth (FOM), lower alveolus (LA), and retromolar trigone (RMT) ≤4 cm in size.

Retrospective study of 96 patients with SCC of the FOM, LA, and RMT undergoing primary surgical treatment.

Original pathology reports and slides were reviewed by three pathologists. Level of bone invasion was categorized as cortical or medullary. Main outcome measures were local control (LC) and overall survival (OS).

Bone invasion was present in 31 cases (32%). On review of pathology slides, all cases of bone invasion demonstrated medullary involvement. Median follow-up was 36 months for all patients, and 53 months for patients not dying from cancer. Among tumors ≤4 cm, bone invasion was associated with significantly worse LC (P =.04) and OS (P =.0005). Medullary invasion (hazard ratio: 2.2, 95% confidence interval: 1.1-4.4, P =.03), postoperative radiotherapy (hazard ratio: 0.3, 95% confidence interval: 0.1-0.5, P <.001), and positive pathologic nodal status (hazard ratio: 4.1, 95% confidence interval: 1.9-8.6, P <.001) were independent predictors of worse OS among the entire cohort.

Mandibular medullary bone invasion is a poor prognosticator in oral cancers, irrespective of small size of primary tumor. Such cases should be considered for postoperative radiotherapy.

4. Laryngoscope, 127:849-854, 2017.