Endoscopic Nasopharyngectomy

Introduction

Certain ethnogeographic groups have been found to have an increased risk of developing nasopharyngeal carcinoma (NPC). Studies have shown that among the Chinese, there is a very high incidence of NPC affecting 10 to 20 per 100,000 for men and 5 to 10 per 100,000 for women, causing NPC to sometimes be called the “Cantonese cancer.” Most of these NPCs originate in the epithelial lining of the fossa of Rosenmüller, an area located posteromedially to the medial crura of the opening of the Eustachian tube.

Screening, diagnosing, and monitoring NPC can now be done using several serological markers after studies demonstrated that a close relationship existed between NPC and the Epstein-Barr virus (EBV), a double-stranded DNA virus. Most NPCs carry the clonal EBV genomes and express EBV proteins. To screen the general population, serological markers such as EBC VCA IgA and DNase are used. RT-PCR methods that measure EBV DNA copy numbers in plasma are used to monitor the response to treatment and for early detection of local recurrence.

Currently, radiation therapy (RT), chemotherapy, or combinations of both are the primary available modalities for treating NPC. More than 80% local control can be achieved through RT because of the high radiosensitivity of NPC, giving patients with early NPC a good possibility for cure. However, for patients with advanced-stage locoregional NPC, the standard treatment is Cisplatin-based chemoradiotherapy with or without neoadjuvant chemotherapy. In spite of its high radiosensitivity, patients with advanced NPC still have a 10% to 30% risk of local failure after the initial RT treatment. If local recurrence is suspected, performing a biopsy under nasopharyngoscopy should be done.

Key Operative Learning Points

• Perform medial maxillectomy and posterior septectomy to improve exposure and increase the working space area.

• Use the two nostrils/four hands technique.

• Resection with LASER on a curved applicator.

• Mark the deep margin of resection as the pharyngobasilar fascia and remove the Eustachian tube cartilage as far laterally as possible.

• Involvement of the bone of the skull base will require a navigation-guided endoscopic resection.

Preoperative Period

NPC patients who are monitored using the EBV serological markers typically do not complain of any symptoms. When there is a local recurrence, the NPC patient may experience the same symptoms experienced at the initial presentation of the cancer. The presence of a mass in the fossa of Rosenmüller or even from the nasopharynx should be investigated further for rNPC. However, there are some patients with whom careful nasopharyngeal examination does not reveal any obvious mucosal lesion. Some may appear as a small submucosal swelling beneath an intact mucosa. Therefore, performing a biopsy under nasopharyngoscopy is mandatory to establish the diagnosis of local recurrence.

The surgeon must evaluate the extent of the cancer by endoscopic examination as well as imaging studies. Magnetic resonance imaging (MRI) is superior in demonstrating soft tissue involvement compared with computed tomography (CT) scan. MRI is able to identify local recurrence, perineural invasion, skull base involvement, suspicious retropharyngeal lymph nodes, and cervical metastasis as well as early cancers that produce mild thickening of the mucosa. These advantages provide important information for good surgical planning and tumor mapping for endoscopic nasopharyngectomy. Salvage surgery is relatively contraindicated for patients who have distant metastasis.

A complete examination of the head and neck must be carried out, particularly in the nasal cavity and nasopharynx, to detect the presence of metastatic lymph nodes, including examination of the cranial nerves. Other important preoperative preparation includes ascertaining any anatomical variation, intraoperative navigation (in selected cases), blood-group matched packed red cells, and preoperative antibiotic. Patients with preexisting significant comorbidities should receive special attention. Anticoagulants or antiplatelet medications should be withheld (if possible) prior to endoscopic nasopharyngectomy.