Digital volume tomography in the assessment of mandibular invasion in patients with squamous cell carcinoma of the oral cavity – A prospective study

Abstract

Cancers in the upper part of aero digestive tract comprises 5% of all the malignancies, most common among them is the squamous cell carcinoma (Acton et al., 2000). The incidence and prevalence of oral squamous cell carcinoma (OSCC) in Indian subcontinent is relatively high because of prevalent habits like chewing tobacco, betel quid and areca-nut which increases the risk of developing OSCC (Feller and Lemmer, 2012). Tumor adjacent to the mandible can invade bone, either by direct extension (Huntley et al., 1996) or by the perineural infiltration (Carter and Pittam, 1980). There are no clear guidance to state the amount of bone resection required beyond the tumor, and in majority of the cases soft tissue extension of the tumor determines the amount of resection (Brown et al., 1994). The decision to maintain the continuity of the mandible demands thorough understanding of the anatomy as well as proper assessment of tumor extension (Huntley et al., 1996). Preoperatively it is difficult to assess the degree of mandibular bone involvement, because there is no single imaging tool available to evaluate the extent of bone invasion 100% accurately (Singh, 2008). Different modalities including clinical examination, plain radiographs, conventional computed tomography (dentascan), magnetic resonance imaging (MRI) and nuclear medicine studies have been studied (Ziegler et al., 2002). Conventional radiographs in the form of orthopantomograph (OPG) provides a decent survey of the mandible, but bone mineral loss should be 30–50% before any change is seen (Huntley et al., 1996, Van Cann et al., 2008) Radionuclide bone scintigraphy utilizing radio-active labeled phosphate compounds along with OPG improves diagnosis in the preoperative evaluation. But this high sensitivity is escorted with very low specificity. Periodontal diseases, infections, infarctions and soft tissue involvement in and around the mandible will show a false positive result (Huntley et al., 1996). MRI is less useful in evaluating the cervical bone involvement due to the absence of signal from cortical bone because of less number of mobile hydrogen ions (Huntley et al., 1996, Boeddinghaus and Whyte, 2008). Digital volume tomography (DVT) is a recent imaging technology. DVT is capable of higher special resolution than dentascan (Genden et al., 2005). So the purpose of this study is to evaluate the diagnostic accuracy of DVT in contrast with OPG, dentascan and histological study in assessing the invasion of mandible of patients with OSCC, clinically adjacent or fixed to the mandible.