Staging significance of bone invasion in small-sized (4 cm or less) oral squamous cell carcinoma as defined by the American Joint Committee on Cancer

Abstract

Objectives: The staging significance of bone invasion is controversial in oral squamous cell carcinoma (OSCC) cases with tumors measuring 4 cm or less according to the American Joint Committee on Cancer (AJCC). Our aim was to retrospectively examine a large group of patients with OSCC to determine the staging significance of bone invasion. Materials and Methods: Three hundred and twenty-three patients with primary OSCC were classified based on tumor size. Mandibular bone invasion was categorized as absent, one side bone, and both buccal and lingual bones, and analyzed for association with disease progression. Regional lymph node metastasis (N), perineural invasion, vascular invasion, surgical margin involvement, and adjuvant treatment were also analyzed. Results: In all OSCC cases, bone invasion (p=0.007) with stage N, perineural invasion, and surgical margin involvement were significant independent prognostic factors of disease progression. However, in OSCC cases with tumors measuring 4 cm or less, bone invasion was not significantly associated with disease progression. Nevertheless, invasion of both buccal and lingual bones was significantly associated with disease progression (p=0.03). In multivariate analysis, both buccal and lingual bone invasion (p=0.04

hazard ratio=3.4

95% confidence interval, 1.0–11.0), stage N2, and perineural invasion were also independent prognostic factors. Kaplan-Meier analyses indicated that OSCC cases with one sided bone invasion can be upstaged by one T stage. Conclusion: Although OSCC bone invasion was an independent prognostic factor, bone invasion in small OSCC was not. The AJCC T system is of limited prognostic value for small OSCC with bone invasion. However, small OSCC with both buccal and lingual bone invasion had a significantly worse prognosis. Therefore, we recommend a revision of the T staging system such that tumors are classified as T1 to T3 based on size, and mandibular OSCCs with both buccal and lingual bone invasion should be defined as T4. The remaining groups should be upstaged by one T stage in the presence of bone invasion.