Bone scanning in the assessment of mandibular invasion by oral cavity carcinomas.

Mandibular invasion alters the staging and treatment of oral cavity squamous cell carcinoma, and thus its detection is essential to the head and neck oncologist. There is little information assessing the accuracy of the radionuclide bone scan and the roentgenogram in determining mandibular invasion. The present study reports data on 40 patients with squamous cell carcinoma of the oral cavity for whom bone scans, mandibular roentgenograms, and histologic examination of the mandible were available. The bone scan correctly predicted mandibular invasion in 8 of 9 cases; the false positive rate was 53% as a result of mandibular inflammatory changes. The bone scan was more accurate than the roentgenogram in predicting tumor invasion of the mandible, but the bone scan had a higher false positive rate. A normal bone scan and roentgenogram virtually precluded tumor involvement of the mandible. We conclude that the bone scan is an important adjunct in the prediction of carcinomatous invasion of the mandible in squamous cell carcinoma of the oral cavity.