Investigative modalities of mandibular invasion by squamous cell carcinoma

Objectives/Hypothesis: To compare preoperative investigations with histological findings in squamous cell carcinoma (SCC) of the oral mucosa that abuts the mandible. Both clinical and radiological examinations fail to predict accurately invasion of the mandible by intraoral SCC, Study Design: This two-part, prospective study is of a consecutive series of patients whose first malignancy of the upper aerodigestive tract abutted the lingual surface of the mandible. Methods: All patients presented to the Queensland Radium Institute Head and Neck Clinic between 1993 and 1997 with a biopsy-proven SCC that abutted the mandible. These tumors were investigated clinically, radiologically, and histologically. Sensitivity, specificity and predictive values were calculated for various approaches, In the second part of the study, single photon emission computed tomography (SPECT) bone scans were included. Quantification ratios of bone scans compared the average counting statistics in visually identified mandibular abnormal uptake with normal cervical spine and jaw. Results: Sixty-seven patients were followed for 55 months and assessed with orthopantomogram (OPG), computed tomography (CT) scans, and, in the second part of the study, SPECT bone scans. Thirty-six tumors showed histological evidence of bony invasion. Bony involvement was suggested by OPG in 36 and confirmed histologically in 27 patients. CT scans showed evidence of bone invasion in 22 cases, with 18 of these histologically confirmed Technetium 99m methylene diphosphonate (MDP) bone scans with planar imaging and SPECT were performed in 24 patients, and histological appearance was suitable for analysis in 14. Three patients with tumor (cervical spine ratios greater than 1.5 predicting malignant involvement) had this confirmed histologically. Conclusions: The first part of the study confirms our hypothesis that currently used investigations, as well as clinical assessment, fail to predict accurately invasion of the mandible by intraoral SCC. The second part suggests that SPECT scanning with high quantification ratios is promising in the prediction of tumor involvement.