Mandibular sclerosis seen on CT can signal invasion by squamous cell carcinoma

By Erik L. Ridley, staff writer

May 19, 2000 --

The presence of mandibular sclerosis should increase suspicion of invasion by squamous cell carcinoma of the oral cavity (SCCOC), according to research presented at the centennial meeting of the American Roentgen Ray Society in Washington, DC.

Mandibular invasion can be identified on a CT exam by erosion of the cortical surface of the mandible, according to Dr. David Isaacs of the University of North Carolina School of Medicine in Carrboro, NC. The significance of a sclerotic appearance to underlying bone has not been studied, however.

To evaluate the significance of mandibular sclerosis, a UNC research team evaluated 31 patients with SCCOC but no evidence of direct cortical invasion on pre-operative CT prior to mandibulectomy. All patients underwent contrast-enhanced CT with contiguous 3-5 mm thick sections and reconstruction using soft tissue and bone algorithms.

One head and neck radiologist read the studies. Six of the 31 patients were diagnosed with mandibular sclerosis adjacent to the tumor, while 25 had no evidence of sclerosis.

The CT findings were correlated with histologic evidence of bone invasion and sclerosis. In the six patients with sclerosis, three had microscopic evidence of bone invasion on pathology, while the other three did not.

In the 25 patients without sclerosis, two were found to have bone invasion on pathology. The researchers found the increased rate of invasion in patients with sclerosis to be statistically significant (p=.038).

"The presence of sclerosis in the mandible may be an early indication of microscopic disease and should increase the suspicion of mandibular invasion of squamous cell carcinoma in the oral cavity," Isaacs said.

In related research, Isaacs also presented the UNC team's evaluation of the diagnostic accuracy of high-resolution CT in detecting such mandibular invasion. While CT has been viewed by many to be the best imaging modality for this application, previously published studies have raised doubts because of the varying accuracy reported for the technique, Isaacs said.

In this study, the UNC group tracked 49 patients with SCCOC treated by mandibulectomy, all of whom underwent preoperative contrast-enhanced CT (contiguous 3-mm-thick sections) through the primary site.

Studies were reconstructed using a high-resolution soft tissue and bone window algorithm. One head and neck radiologist retrospectively reviewed the studies for erosion, as evidenced by absence of mandibular cortex adjacent to the tumor. Imaging results were then compared to histologic findings.

The CT study correctly identified 25 of 26 cases with mandibular SCCOC invasion, and correctly excluded invasion in 20 of 23 cases, according to the researchers. Based on these results, the use of CT for detecting mandibular invasion had a sensitivity of 96%, specificity of 87%, positive predictive value of 89%, and a negative predictive value of 95%.

"We recommend that all patients with tumor adjacent to the mandible be evaluated pre-operatively by CT," Isaacs said.

By Erik L. Ridley staff writer
May 19, 2000

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