MRI of local disease in nasopharyngeal carcinoma: tumour extent vs tumour stage.

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Abstract
The purpose was to use MRI to study in detail local tumour extension in patients presenting with nasopharyngeal carcinoma (NPC) and to compare the extent of local disease with the current T-stage classification. MR images of 150 patients with newly diagnosed nasopharyngeal carcinoma were obtained on a 1.5 T unit. 10 extranasopharyngeal sites were analysed for tumour involvement. The number of concurrently involved sites was determined. The extent of tumour invasion was compared with staging as defined by the fifth edition of the AJCC classification. The T-stage distribution was T1 21%, T2 16%, T3 41% and T4 22%. The frequencies of tumour invasion into an individual site, and the mean number of other concurrently involved sites were as follows: skull base 63%, 3.9 sites; parapharyngeal 56%, 3.9 sites; nasal cavity 53%, 4.0 sites; oropharyngeal 17%, 5.2 sites; sphenoid sinus 27%, 5.6 sites; cranium 21%, 5.7 sites; infratemporal fossa 2%, 6.3 sites; ethmoid sinus 14%, 6.5 sites; orbit 5%, 7.0 sites; maxillary sinus 5%, 7.1 sites; and hypopharynx 0%, 0 sites. Extranasopharyngeal extension commonly occurred superiorly into the skull base rather than inferiorly to the oropharynx (p < 0.0001). Anatomical sites defined within the same T-stage category had different frequencies of involvement and different frequencies of concurrently involved sites. Oropharyngeal involvement (T2 stage) was associated with a number of concurrently involved sites comparable to structures in the T3 category. Maxillary and ethmoid sinus involvement (T3 stage) were associated with a number of involved sites comparable to the T4 stage. Invasion of the maxillary antrum and orbit are markers of the most bulky form of NPC.