The prognostic and staging implications of bone invasion in oral squamous cell carcinoma

BACKGROUND: A study was undertaken to determine whether bone invasion is an independent prognostic factor in oral squamous cell carcinoma (SCC) after taking into account the extent of bone invasion. METHODS: The study was a retrospective review of 498 patients with oral SCC undergoing surgery with curative intent, 102 of whom had pathologically proven bone invasion. Bone invasion was categorized as absent, cortical, or medullary and tested for association with disease control and survival. RESULTS: After adjusting for potential confounding factors in multivariate analysis, there was no association between cortical invasion and overall (P =.48) or disease-specific survival (P =.63). In contrast, medullary invasion was an independent predictor of reduced overall (hazard ratio [HR, 1.9; 95% confidence interval [CI, 1.2-3.1; P =.006) and disease-specific survival (HR, 2.1; 95% CI, 1.2-3.6; P =.01), and this appeared to result from an increased risk of distant metastatic failure (P =.037) rather than local (P =.51) or regional recurrence (P =.14). Within the subset of patients with medullary invasion, survival differed significantly according to tumor size (P =.029). CONCLUSIONS: Patients with oral SCC and bone invasion have widely variable outcomes depending on the depth of bone invasion and tumor size. The results suggest that the current American Joint Committee on Cancer staging system, which classifies all tumors invading through cortical bone as T4, has limited prognostic utility. The authors recommend a revision of the T staging system such that tumors are classified as T1 to T3 based on size and then upstaged by 1 T stage in the presence of medullary bone invasion.