(11) The Utility of Cone-beam Computed Tomography for the Evaluation of Invasion by Mandibular Squamous Cell Carcinoma

Abstract: Purpose
The degree of bone involvement in mandibular squamous cell carcinoma has a significant impact on surgical planning. While precise evaluation of bone involvement is needed, no single imaging method is able to detect the extent of invasion with complete reliability.1,2 The purpose of this preliminary study was to determine the utility of cone-bean computed tomography (CBCT) for the evaluation of invasion by mandibular squamous cell carcinoma.

Patients and Methods
A retrospective chart review was conducted to identify subjects treated for oral squamous cell carcinoma (OSCC) at John Peter Smith Hospital from 2019 to 2022. All subjects had OSCC adjacent or fixed to the mandible, received preoperative CBCT and multi-slice computed tomography scan (MSCT), and had resection specimens that included bone. Preoperative staging and resection type was determined by the senior author based on clinical examination and radiographic findings. To determine the radiographic presence of mandibular invasion, all CBCT scan reads were completed by a single radiologist while MSCT scan reads were completed by a separate radiologist. Radiographic reads were classified as having no bone involvement, bone erosion, or bone invasion and compared to the histological analysis of bone. The primary predictor variable was radiographic modality (CBCT or MSCT). The primary outcome variable was the diagnostic accuracy of CBCT as determined by histological analysis.

Results
Twenty-one subjects met the inclusion criteria. The average age of the cohort was 59 years (SD 12). There were 11 males and 10 females. At presentation, 11 subjects were fully dentate, 8 were partially dentate, and 2 were edentulous. The preoperative staging for the included subjects was: 16 stage 4, 2 stage 3, 1 stage 2, and 2 stage 1. The anatomic regions involved were: 10 retromolar trigone, 7 alveolar process, 4 floor of mouth. Sixteen subjects received a segmental resection and 5 received a marginal resection. There was histologic evidence of cortical erosion or invasion in 13 cases. The sensitivity of CBCT was 100% (95% CI 0.75-1), the specificity was 75% (95% CI 0.35-0.97), the positive predictive value was 87% (95% CI 0.66-0.96), and the negative predictive value was 100% (95% CI 0.58-1). The calculated test efficiency was 91%. The sensitivity of MSCT was 92% (95% CI 0.64-0.99), the specificity was 100% (95% CI 0.63-1), the positive predictive value was 100% (95% CI 0.69-1), and the negative predictive value was 89% (95% CI 0.76-0.99). The calculated test efficiency was 95%.

Conclusions
CBCT provides meaningful data that may be useful in identifying erosion or invasion in patients with mandibular squamous cell carcinoma.

References
[1] Hendrikx AW, Maal T, Dieleman F, Van Cann EM, Merkx MA. Cone-beam CT in the assessment of mandibular invasion by oral squamous cell carcinoma: results of the preliminary study. Int J Oral Maxillofac Surg 39(5):436-9, 2010
[2] Hakim SG, Wieker H, Trenkle T, Sieg P, Konitzer J, Holl-Ulrich K, Jacobsen HC. Imaging of mandible invasion by oral squamous cell carcinoma using computed tomography, cone-beam computed tomography and bone scintigraphy with SPECT. Clin Oral Investig 18(3):961-7, 2014