COMPARISON OF INTRAORAL ULTRASOUND, COMPUTED TOMOGRAPHY AND HISTOPATHOLOGY IN ASSESSMENT OF DEPTH OF INVASION IN BUCCAL MUCOSA CANCERS – A CROSS-SECTIONAL STUDY

Abstract

BACKGROUND: Head and neck cancers account for 30% of malignancies in India among which oral squamous cell carcinoma is the most common. Among the oral squamous cell carcinomas, the buccal mucosa cancers and lower gingivobuccal sulcus complex cancers are more common in our region due to addiction to tobacco and betel quid chewing. The majority of patients presenting here are females belonging to low socioeconomic status with locally advanced diseases that require major surgery and adjuvant treatment with significant morbidity. Depth of invasion shows the true infiltrative potential of a tumor. Following the study by Ebrahimi, the 8th edition of the American Joint Committee on Cancer (AJCC-TNM) staging incorporated depth of invasion as one of the features for preoperative tumor staging.1 Depth of invasion is usually measured preoperatively using imaging technique by Contrast enhanced Computed Tomography Scan or Magnetic resonance imaging and postoperatively from resected specimens by histopathological examination which is the gold standard method. Ultrasound evaluation is widely being used for assessment of thyroid nodules and metastatic lymph nodes in neck. Imaging also has limitations in assessing cancers involving the alveoli, palate and retromolar trigone as the periosteum is just deep to the mucous membrane. xviii OBJECTIVES: 1) To perform Intraoral ultrasound and contrast enhanced Computed Tomography preoperatively on patients with squamous cell carcinoma of the buccal mucosa and document the depth of invasion by using these modalities. 2) To document depth of invasion in resected specimens of these patients with squamous cell carcinoma of Buccal mucosa by Histopathological examination. 3) To compare depth of invasion documented by Intraoral ultrasonography and computerized tomography with depth of invasion assessed by Histopathological examination and thereby evaluate the reliability of these preoperative imaging modalities. METHODS: The study included 42 patients with biopsy proven squamous cell carcinoma of Buccal mucosa staged T2 or T3 planned for composite resection and adjuvant treatment at R.L. Jalappa Hospital And Research Centre, Kolar from July 2022 – May 2024. The pre-operative depth of invasion was documented by using intraoral ultrasound and Contrast enhanced computed tomography. All these patients underwent composite resection of the oral cavity tumor (including marginal or hemimandibulectomy) with neck dissection and reconstruction. The resected specimen was subjected to Histopathological examination where the tumor thickness, depth of invasion, bony involvement, perineural involvement, lymph node involvement and extracapsular spread were documented. The patients were administered adjuvant treatment in the form of post-operative radiotherapy or radiotherapy plus chemotherapy. The patients were followed up for a minimum of 6 months after xix completion of the treatment and any local, regional or loco-regional recurrence was documented. RESULTS: In our study, the majority of patients were females (79%) aged more than 60 years, and the most common site was left buccal mucosa. Out of the 19 patients staged T2 clinically, 5 patients were down-staged to T1 and 4 patients who were staged T3 by clinical and radiological examination were down-staged to T2, whereas 2 patients were upstaged to T4a due to skin involvement on histopathology. The DOI assessed by intraoral ultrasound correlated with that measured on histopathology in 71.5% of cases whereas in CECT it was 26.2 % with a Karl Pearson correlation coefficient of 0.929 between intraoral ultrasound and histopathology. The intraoral ultrasound overestimated DOI in 21.4% of cases. Nodal staging of the patient was also compared and 4 patients were upstaged to N3b due to ENE in histopathology. 13 patients were down-staged to N0 since it turned out to be reactive lymph nodes. Patients underwent surgery, followed by adjuvant radiotherapy in 61.9 % and adjuvant chemoradiotherapy in 21.4 %. Disease-free survival was seen in 81 % of the patients and locoregional recurrence was seen in 16.6% of the patients. CONCLUSION: There is a high prevalence of Oral squamous cell carcinoma in the region of Kolar, with the majority of the patients being female (79%) due to addiction to tobacco. There may be a significant difference in the DOI assessed radiologically when compared to histopathology, thereby affecting treatment planning and outcome. The depth of invasion assessed by intraoral ultrasound correlates much better with that measured on histopathology when compared to that measured by CECT in buccal mucosa cancers staged T2 or T3. Intraoral ultrasound is a better preoperative imaging modality for determining the depth of invasion in buccal mucosa cancers compared to CECT.