Abstract
From January 1988 to September 1995, 29 patients with nasopharyngeal carcinomas were examined with MR imaging and CT before and after radiotherapy. In our series, 66% of the patients (19 of 29) were classified as stage T4 when MR imaging as well as CT was used in T staging based on the fourth edition of the UICC stage classified system. In the fourth edition, only one of 7 patients with T1-T3 disease had local recurrence, while 5 of 18 patients with T4 tumors recurred locally. In the fifth-edition system, only one of 7 patients with T1-T2 disease had local recurrence, while 5 of 18 patients with T3-T4 tumors recurred locally. However, the local control rate was similar between T3 and T4 tumors.
In the fifth edition, T2 is divided into T2a and T2b according to the presence of infiltration of tumor beyond the pharyngobasilar fascia. All 7 patients without invasion of the pharyngobasilar fascia had local control. However, it was impossible to detect obliteration of the pharyngobasilar fascia with CT, meaning that MRI is indispensable for classifying the stage based on the fifth edition. It was also difficult to identify invasion of the sinus of Morgagni with CT, but MR imaging identified it much more clearly. MR imaging was also better than CT at detecting invasion of the posterior, posterolateral, and superolateral part of the skull base.
According to the fourth edition, 6 of 15 patients with N2c or N3 disease had distant metastases, while only 1 of 9 patients with N1-2b disease did. Based on the fifth edition, 4 of 5 patients with N3 disease had distant metastases. The fifth edition incorporated deep invasion of tumors investigated with CT and MR imagings into its Tstage classification and is more rational than the fourth edition. It expected to be a better prognostic factors.
