DentaCT for evaluating mandibular and maxillary invasion in cancer of the oral cavity

Mandibular conservation in oral cancer

Surgery is one of the established modes of initial definitive treatment for a majority of oral cancers. Invasion of bony or cartilaginous structures by advanced upper aero-digestive tract cancer has been considered an indication for primary surgery on the basis of historic experience of poor responsiveness to radiation therapy [1]. The mandible is a key structure both in the pathology of intra-oral tumours and their surgical management. It bars easy surgical access to the oral cavity, yet maintaining its integrity is vital for function and cosmesis. Management of tumours that involve or abut the mandible requires specific understanding of the pattern of spread and routes of tumour invasion into the mandible. This facilitates the employment of mandibular sparing approaches like marginal mandibulectomy and mandibulotomy, as opposed to segmental or hemimandibulectomy which causes severe functional problems, as the mandibular continuity is lost. Accurate preoperative assessment that combines clinical examination and imaging along with the understanding of the pattern of spread and routes of invasion is essential in deciding the appropriate level and extent of mandibular resection in oral squamous cell carcinoma. Studies have shown that local control rates achieved with marginal mandibulectomy are comparable with that of segmental mandibulectomy. In carefully selected patients, marginal mandibulectomy is an oncologically safe procedure to achieve good local control and provides a better quality of life. This article aims to review the mechanism of spread, evaluation and prognosis of mandibular invasion, various techniques and role of mandibular conservation in oral squamous cell carcinoma.

Evidence for imaging the mandible in the management of oral squamous cell carcinoma: a review

The accuracy of clinical examination, peroperative periosteal stripping and imaging techniques in predicting tumour invasion of the mandible in oral cancer so far reported have been compared according to their specificity and sensitivity. Clinical examination alone was not shown to be accurate, but periosteal stripping at the time of resection was extremely accurate although so far only one study has investigated it. No single imaging technique will accurately predict the invasion of tumour into the mandible, but a combination of an orthopantomogram and bone scintigraphy is recommended in early invasion. Magnetic resonance imaging is more sensitive than computed tomography and therefore may be more useful if mandibular invasion requires consideration. The decision to resect the mandible as part of the management of oral cancer should be taken on the evidence of clinical examination, periosteal stripping and at least two imaging techniques that complement each other in terms of specificity and sensitivity.

[Analysis of epidermoid carcinomas using panoramic radiography and computerized tomography]

The purpose of this work was to compare radiographic findings, such as localization and extension of tumors toward the bone and soft tissues, in panoramic radiography and computed tomography (CT). Four radiologists assessed the radiographic findings of 48 patients with the histopathological diagnosis of squamous cell carcinoma in different sites of the maxillofacial region. Panoramic radiographs and computed tomographs were obtained at the University of Iowa Hospitals and Clinics, at FUNDECTO-USP and at the hospital of the University of São Paulo (USP). We observed a considerable limitation of the panoramic radiography in determining the localization and extension of tumors, since it revealed unclear delimitations. Regarding CT, better results were obtained: it was possible to observe the invasion of the tumor toward adjacent soft tissues, as well as the extension of bone destruction and the depth of the lesion, which were confirmed by surgical findings. We concluded that computed tomography demonstrated to be a sensitive radiographic technique for the detection of the involvement of bone and soft tissues, contributing for a more precise diagnosis, surgical planning and intervention. On the other hand, panoramic radiography was considered less sensitive and less efficient than CT, since it shows only unclear borders of the lesions and is not able to assess the involvement of soft tissues.

Technetium 99m single positron emission computed tomography scanning for assessing mandible invasion in oral cavity cancer

OBJECTIVES

To study the accuracy of single positron emission computed tomography (SPECT) scanning and compare its results to clinical examination, Panorex, and computed tomography (CT) scanning with respect to determining mandibular invasion by oral cavity and oropharyngeal cancer, and to define the role of SPECT scanning in the preoperative assessment of oromandibular cancer.

STUDY DESIGN

Prospective study of 38 patients who underwent technetium 99m SPECT scanning as part of their preoperative clinical assessment for cancer at risk of invading the mandible. All patients underwent partial or segmental mandibulectomy as part of their surgical management.

METHODS

A data protocol was used to tabulate patient demographics, tumor characteristics and results of preoperative tests as patients were enrolled into the study. Following surgical treatment, these data were correlated with histopathological findings. Detailed analysis was performed to assess the tabulated data.

RESULTS

The SPECT scanning demonstrated an 87% overall accuracy in predicting bone invasion compared with 71% for clinical examination, CT scanning, and Panorex x-rays. The SPECT scanning was significantly more sensitive (95%) than either CT scans (55%) or Panorex x-rays (50%). Notably SPECT scanning demonstrated a considerable improvement in specificity (72%) compared with conventional radionuclide scanning. Although not as specific as CT scanning or plain films, SPECT scanning was significantly more effective in ruling out disease than was clinical examination.

CONCLUSIONS

Preoperative SPECT scanning used in combination with clinical examination, CT scanning, and Panorex x-rays to assess patients at risk for mandible involvement by oral cavity cancer can improve the accuracy of predicting bone invasion and help in appropriate treatment planning so as to safely reduce the proportion of disease-free jaws resected.