13 Head and Neck - Oropharynx

Head and Neck - Oropharynx

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THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 15/02/2021

Figure 1: Anatomy of oropharynx (from headneckcancer.org)

3. ANATOMICAL TOPOGRAPHY

5. WORK UP

The oropharynx communicates anteriorly with the oral cavity, above with the nasopharynx, and below with the hypopharynx and the larynx. Its walls are anteriorly formed by the base of tongue, laterally by the two tonsillar regions, above by the soft palate, and posteriorly by the posterior pharyngeal wall (Figure 1). A transverse plane passing through the lingual insertions of the palatoglossal folds, laterally by the glosso-tonsillar sulci, and posteriorly by the glosso-epiglottic sulcus or vallecula, limits the base of tongue anteriorly. The faucial arch is composed of the two tonsillar regions and the soft palate. The tonsil lies in a fossa formed by the anterior and posterior tonsillar pillars. This is separated from the tongue by the glosso-tonsillar sulcus. The two pillars merge and superiorly form the soft palate, which is anteriorly adherent to the hard palate and inferiorly supports the uvula. The oropharynx has a rich lymphatic plexus draining for the most part to the upper anterior cervical or sub digastric lymph nodes (Level II nodes) .

• Documentation of history in detail is important. History of smoking, alcohol, sexual practices and comorbidities is necessary as this can be of prognostic value [3] • Detailed clinical examination including inspection and palpation of the primary site and neck should be done. Fibreoptic endoscopic evaluation is necessary. Detailed documentation of all mucosal extensions is extremely important as these may not be well visualised on imaging. A clinical diagramdelineating the primary with all disease extensions is helpful for planning of BT (Figure 2). • It is recommended to place radio-opaque markers or tattoos at 4 edges of the tumour for improving the target volume delineation (Figure 3). • Wherever possible clinical photographs should be taken (Figure 4). These are helpful while planning insertions of BT catheters. • Routine blood investigations such as full blood count, liver and renal function tests, viral markers and electro-cardiogram. • Evaluation under anaesthesia for disease mapping is important. This is also helpful for BT planning. • Biopsy for histopathology. P16 evaluation with immunohistochemistry should be done. • Imaging: Contrast enhanced CT scan of the head and neck region with slice thickness of ≤ 5mm is considered standard. Magnetic resonance imaging (MRI) has been proved to be better for soft tissue delineation of oropharynx especially infiltration of muscles in the base of the tongue as well as soft tissue extensions in a soft palate primary. Positron emission tomography (PET) CT scan could be considered in selected cases. Role of PET CT in delineation of the target volume is evolving. • Imaging of thorax: CT scan of the thorax or chest X ray should be done. • Dental evaluation which includes fluoride gel application, scaling and management of caries is mandatory. [20]

4. PATHOLOGY AND STAGING

Squamous cell carcinoma accounts for 95% of the cancers of the oropharynx. Other uncommon histopathologies include lymphomas, sarcomas and minor salivary gland tumours. Brachytherapy is considered only for squamous cell carcinoma of the oropharynx.