The nasopharynx is the air passageway at the upper part of the pharynx (throat) behind the nose and lies just above the soft palate (Fig.1 Coloured pink). The nostrils lead through the nasal cavity into the nasopharynx. An opening on each side of the nasopharynx (called the Eustachian tube opening) leads into the middle ear on each side. Inferiorly, it communicates with the oropharynx (part of pharynx behind the oral cavity).
Several types of tumours can develop in the nasopharynx. Some of these tumours are benign (non-cancerous), but others are malignant (cancerous). Several types of benign tumours, including angiofibromas, hemangiomas etc.
The nasopharynx contains several types of tissue, and each contains several types of cells. Different cancers can develop in each kind of cell. The differences are important because they determine the seriousness of the cancer and the type of treatment needed. Squamous cell carcinoma (nasopharyngeal carcinoma – NPC) is the most common malignant tumour of the nasopharynx. Other nasopharyngeal cancers include adenoid cystic and mucoepidermoid carcinomas, malignant mixed tumours, adenocarcinomas, lymphomas, fibrosarcomas, osteosarcomas, chondrosarcomas, and melanomas.
NPC is one of the most common cancers among people of Chinese, especially Southern Chinese, and Southeast Asian ancestry, including Chinese immigrants to North America. Over several generations, the prevalence among Chinese-Americans gradually decreases to that among non-Chinese Americans, suggesting an environmental component to etiology. Dietary exposure to nitrites and salted fish also is thought to increase risk. Epstein-Barr virus is a significant risk factor, and there is hereditary predisposition.
Anyone with such symptoms requires careful evaluation and examination with a nasopharyngeal mirror or endoscope, and lesions are biopsied. Open cervical node biopsy should not be done as the initial procedure, although a needle biopsy is acceptable and often recommended. Gadolinium-enhanced MRI (with fat suppression) of the head with attention to the nasopharynx and skull base is done; the skull base is involved in about 25% of patients. CT also is required to accurately assess skull base bony changes, which are less visible on MRI. A PET scan also commonly is done to assess the extent of disease as well as the cervical lymphatics.
Primary treatment of NPC is concomitant chemoradiotherapy, in which chemotherapy is given in combination with radiation therapy. Patients achieve quite satisfactory cure rate. About one third of the patients fail locally in the nasopharynx. Up until recently there were no good treatment options available other than re-irradiation.
Re-irradiation improves survival in less than 30% of patients but associated with high incidence of complications (of reirradiation) like temporal lobe necrosis, trismus, deafness, endocrine dysfunction and osteoradionecrosis causing severe pain, foul odour and massive bleeding. Even though the incidence of complications has come down with intensity modulated radiotherapy (IMRT), the cure rate remains the same.
Removing the tumour (Nasopharyngectomy)
Paul Donald described the Transfacial Subcranial approach for nasopharyngectomy. This has doubled the 5-year survival in patients with recurrent disease.
With newer endoscopic surgical techniques, surgeons can completely remove some nasopharyngeal tumours (endoscopic nasopharyngectomy), but this is appropriate only for a small tumours. Factors determining the surgical approach are the extent of tumourand the structures involved. For planning the surgery, we should know whether the tumour is limited to nasopharynx or spread to infratemporal fossa or involving the internal carotid artery or intracranial extension.
Nasopharyngectomy is indicated as a salvage procedure in persistent or recurrent nasopharyngeal carcinoma. But it is done as a primary treatment in radioresistent tumours like adenocarcinomas, minor salivary gland tumours and sarcomas. These complex procedures are done only in specialized centers.
Cancers of the nasopharynx often spread to the lymph nodes in the neck. These cancers often respond well to treatment with radiation therapy (and sometimes chemotherapy). But if some cancer remains after these treatments, an operation called a neck dissection may be needed to remove these lymph nodes.
