General Information About Nasopharyngeal Cancer
The nasopharynx has a cuboidal shape. The lateral walls are formed by the eustachian tube and the fossa of Rosenmuller. The roof, sloping downward from anterior to posterior, is bordered by the pharyngeal hypophysis, pharyngeal tonsil, and pharyngeal bursa with the base of the skull above. Anteriorly, the nasopharynx abuts the posterior choanae and nasal cavity, and the posterior boundary is formed by the muscles of the posterior pharyngeal wall. Inferiorly, the nasopharynx ends at an imaginary horizontal line formed by the upper surface of the soft palate and the posterior pharyngeal wall.
Unlike other squamous cell cancers of the head and neck, nasopharyngeal cancer does not appear to be linked to excess use of tobacco or moderate alcohol intake (up to 15 drinks a week). Factors thought to predispose to this tumor include the following:
- Chinese (or Asian) ancestry.
- Epstein-Barr virus (EBV) exposure.
- Unknown factors that result in very rare familial clusters.
- Heavy alcohol intake.
Signs and Symptoms
Symptoms and signs at presentation include the following:
- Painless, enlarged lymph nodes in the neck (present in approximately 75% of patients and often bilateral and posterior).
- Nasal obstruction.
- Diminished hearing.
- Recurrent otitis media.
- Cranial nerve dysfunction (usually II–VI or IX–XII).
- Sore throat.
In the patient who presents with only cervical adenopathy, the finding of EBV genomic material in the tissue after amplification of DNA with the polymerase chain reaction lends strong evidence for a nasopharyngeal primary tumor, and a concerted search should be conducted in that area.
Diagnosis is made by biopsy of the nasopharyngeal mass. Workup includes the following:
- Careful visual examination (by fiberoptic endoscopic examination or examination under anesthesia [EUA]).
- Documentation of the size and location of the tumor and neck nodes.
- Evaluation of cranial nerve function including neuro-ophthalmological evaluation and audiological evaluation.
- Computed tomographic (CT) scan or positron emission tomography (PET)-CT scan.
- Magnetic resonance imaging (MRI) to evaluate skull base invasion.
- Chemistry panel.
- EBV titers.
Any clinical or laboratory suggestion of distant metastasis may prompt further evaluation of other sites. Careful dental and oral hygiene evaluation and therapy is particularly important prior to initiation of radiation treatment. MRI is often more helpful than CT scans in assessing skull base involvement and in defining the extent of abnormalities detected.[5-7]
Major prognostic factors adversely influencing outcome of treatment include the following:
- Large tumor size.[Level of evidence: 3iiiA]
- A higher tumor (T) stage.
- The presence of involved neck nodes.
Other factors linked to diminished survival that were present in some, but not all, studies include the following:
- World Health Organization (WHO) grade I.
- Long interval between biopsy and initiation of radiation therapy.
- Diminished immune function at diagnosis.
- Incomplete excision of involved neck nodes.
- Pregnancy during treatment.
- Locoregional relapse.
- Certain EBV antibody titer patterns.
Small cancers of the nasopharynx are highly curable by radiation therapy, and patients with these small cancers have shown survival rates of 80% to 90%.
Moderately advanced lesions without clinical evidence of spread to cervical lymph nodes are often curable, and patients with these lesions have shown survival rates of 50% to 70%.
Follow-up for patients includes the following:
- Routine periodic examination of the original tumor site and neck.
- CT or PET-CT scan.
- MRI scan.
- Blood work.
- EBV titers.
Monitoring of patients should include the following:
- Surveillance of thyroid and pituitary function.
- Dental and oral hygiene.
- Jaw exercises to avoid trismus.
- Evaluation of cranial nerve function, especially as it relates to vision and hearing.
- Evaluation of systemic complaints to identify distant metastasis.
Although most recurrences occur within 5 years of diagnosis, relapse can be seen at longer intervals. The incidence of second primary malignancies is less than after treatment of tumors at other head and neck sites.
Poorly differentiated squamous cell cancer has been associated with EBV antibodies.[4,12] High-titer antibodies to virus capsid antigen and early antigen, especially of high IgA class, or high titers that persist after therapy, have been associated with a poorer prognosis. This finding remains under evaluation.
Tumors of many histologies can occur in the nasopharynx, but this discussion, like the American Joint Committee on Cancer nasopharynx staging, refers exclusively to WHO grade I-, II-, and III-type nasopharyngeal carcinoma.
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