Mandibular invasion in patients with oral and oropharyngeal squamous carcinoma

Invasion of the mandible in squamous carcinoma of the oral cavity and oropharynx has always proved a problem for head and neck oncologists. We studied 82 patients who had mandibulectomies as part of their primary surgical treatment for cancer of these sites. In 40 patients, the tumour appeared to be invading the mandible on clinical grounds and 33 patients had tumours invading the mandible when the latter was examined histopathologically. Multivariate analysis showed that tumour was more likely to be fixed to and clinically invading the mandible in the presence of cancer of the oral cavity, compared with oropharyngeal cancer (P < 0.0001). There was a high degree of correlation between clinical invasion of the mandible and histopathological invasion of the mandible (P = 0.0059). In addition, clinical invasion of the mandible correlated with radiological findings (P = 0.0284). The 5-year survival of those patients with tumour that appeared not to be invading the mandible was 53% compared with 25% for those where tumour did appear to be invading the mandible (P < 0.02). The sensitivity and specificity of clinical evidence of mandibular invasion was calculated with the final arbiter of invasion being the histopathological findings. The sensitivity of clinical examination was 91% and the specificity 80%. The positive predictive value was 75% and the negative predictive value 93%. Mandibular invasion is a poor prognostic sign in cancer of the oropharynx and oral cavity. Detection of invasion prior to operation is obviously extremely important and it appears that clinical findings are an accurate method of predicting invasion.