Purpose: To examine the usefulness of MR imaging for predicting local contr
ol of nasopharyngeal carcinoma (NPC) and the value of MR imaging in the new
ly published fifth edition of the TNM classification.
Methods and Materials: We studied 29 patients with NPC with MR imaging and
CT before and after treatment. Staging was done according to the fourth and
newly published fifth editions of the International Union Against Cancer (
UICC) staging system. The radiotherapy protocol was designed to deliver 66
to 68 Gy to the primary tumor and clinically involved nodes.
Results: MR proved better than CT at identifying obliteration of the pharyn
gobasilar fascia, invasion of the sinus of Morgagni, through which the cart
ilaginous portion of the eustachian tube and the levator veli palatini musc
le pass, invasion of the skull base, and metastases to lymph nodes in the c
arotid and retropharyngeal spaces. All seven patients without invasion of t
he pharyngobasilar fascia had local control. The local control rates of pat
ients with invasion of the skull base were not good (60 to 73%). There was
no apparent relationship between tumor volume determined by T1-weighted MR
images and local control when the tumor volume was more than 20 cc. The new
ly published N staging system appears to successfully identify the high-ris
k group for distant metastasis as N3. In our series, four of five patients
with N3 disease developed distant metastases.
Conclusion: Deep infiltration of the tumor is a more important prognostic f
actor in NPC than tumor volume. Since the newly published T staging system
requires a search for tumor invasion into soft tissue such as parapharyngea
l space and bony structures, MR imaging may be indispensable for the newly
published NPC staging system. (C) 1999 Elsevier Science Inc.