Skull-base invasion of nasopharyngeal carcinoma: magnetic resonance imaging findings and therapeutic implications.

Abstract

To evaluate the value of skull-base abnormality on MRI for predicting local recurrence in nasopharyngeal carcinoma. Between November 1988 and February 1997, 48 patients with NPC were examined with both MRI (1.5 T) and CT prior to radiation therapy. T classification (1987 UICC) based on physical examination and CT findings were T1 in 3 cases, T2 in 22, T3 in 9, and T4 in 14. On MRI, low-intensity tissue with Gd enhancement in the marrow of the skull was considered to be a suspicious finding of skull-base invasion. CT simulation was performed in all patients. The total dose to the primary tumor was 60-75 Gy (mean, 67 Gy). The mean follow-up period was 42 months. All 14 T4 patients had abnormal tissue in the marrow of the skull base on MRI. Thirty-eight percent (13 of 34) of T1-3 patients were suspected to have skull-base invasion based on MRI (0% for T1, 27% [6 of 22] for T2, and 78% [7 of 9] for T3). The 5-year local control rate was significantly different between T1-3 and T4 tumors (97% vs. 69%, p < 0.025) but was not different by the presence of the MRI abnormality in the skull base. Skull-base invasion suspected solely by MRI does not relate to local recurrence provided that careful treatment planning is performed with the aid of MRI and CT simulator.