Current treatment of nasopharyngeal carcinomas includes radiation therapy (RT) alone or combined with chemotherapy and neck dissection. Consequently all patients with nasopharyngeal carcinomas are treated with RT. To evaluate the CT and MRI appearance of nasopharyngeal carcinomas treated with RT and the ability of CT and MRI to differentiate persistent or residual tumour from radio-induced changes of head and neck tissues.

Post-treatment CT and MRI examinations of 28 patients with primary nasopharyngeal cancers treated with RT (6000–7500 cGy) were retrospectively evaluated.

We divided the patients in three groups on the basis of the differences in the CT and MRI appearance of the primary tumours treated with RT 1. Responders (9 patients): complete resolution of tumour or reduction in tumour size = or > 75%; 2. Non-Responders (8 patients): persistent tumour or residual mass with reduction in tumour size = or < 50%; 3. Partial Responders: (11 patients) persistent residual mass with reduction in tumour size from 50% to 75% or persistent asymmetry of the mucosal surface.

There are some points to analyse in the interpretation of CT and MRI imaging of post-treated nasopharynx:

Transient changes of irradiated soft tissues are more prominent during the first three months after RT (increased en-hancement of the pharyngeal mucosa and thickening of the pharyngeal walls).

Persis-tent changes are subgrouped in 1. Soft tissue changes: a. Glandular (major salivary glands scialoadenitis and fatty degeneration); b. Deep (reticulation and fibrous degeneration of pre- and post-styloid parapharyngeal fat; c. Visceral (retraction of the pharyngeal wall and distorsion of lateral recess); d. Nervous (radio-induced damage of the CNS such myelopathy and radionecrosis. 2. Bone tissue changes: a. Fatty degeneration of bone marrow of the skull base; b. Sclerosis of the cortical bone of the basisphenoid. 3. Sinonasal changes: Reactive chronic sinusitis.

Perineural-perivascular spread and skull base erosion is indicative of a poor outcome.

The patients of the third group may also be followed with seriated CT because they have a significant percentage of recurrence.