WITH AN estimated incidence rate of 10 to 30 cases per 100,000 persons, nasopharyngeal carcinoma (NPC) is diagnosed in about 1000 people every year in Hong Kong, China. Although chemotherapy is sometimes used, radiotherapy remains the main treatment for NPC. Although the tumor receives the highest dosage of radiation, normal brain tissues along the pathway and brain structures in proximity to the nasopharynx are within the target volume. It is documented that the brainstem, upper cervical spinal cord, cranial and cervical sympathetic nerves, and inferomedial parts of the temporal lobe are exposed to radiation.
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