Tumor Volume Assessment by¹⁸F-FDG PET/CT in Patients with Oral Cavity Cancer with Dental Artifacts on CT or MR Images

The purpose of this study was to investigate the clinical usefulness of PET/CT or CT-attenuated PET in the evaluation of patients with oral cavity cancer (OCC) in whom dental artifacts distorted the conventional CT or MR images of the oral cavity.A PET/CT scan, in addition to a CT or MRI scan, was performed in 69 patients with OCC who had dentures or dental implants. A total of 64 PET/CT, 64 CT, and 27 MR images were analyzed including images from scans performed on 40 patients with OCC without dental artifacts on the conventional images; these were used for comparison. The CT-attenuated PET scan for the detection of primary tumors was compared with the CT or MRI scan. We also evaluated the correlation between the PET/CT volume and the pathologic volume using a regression analysis. In addition, subgroup analysis was performed to determine what proportion of subjects benefited most from the PET/CT.CT-attenuated PET detected more primary tumors than did CT in patients with OCC with dental artifacts (95.3% vs. 75.0%, respectively; P=0.0016). PET/CT volume with a standardized uptake value (SUV) cutoff point of 3.5 predicted the pathologic volume more accurately than did the other cutoff points in patients with OCC with or without artifacts. After comparing pathologic volume and PET/CT(SUV 3.5) volume, the following regression equation was developed: log (pathologic volume)=0.6 x log (PET/CT(SUV 3.5) volume) + 1.3 (R(2) = 0.42, P<0.0001). Subgroup analysis showed that the prediction of the pathologic volume from the PET/CT images was more reliable for tumors that were more than 2 cm in depth (R(2)=0.72).For patients with OCC with dental artifacts on the conventional imaging, PET/CT could provide useful clinical information about the primary tumors, particularly in cases with advanced tumors.