Magnetic Resonance Imaging–Detected Intracranial Extension in the T4 Classification Nasopharyngeal Carcinoma with Intensity-Modulated Radiotherapy

PURPOSE: This study was conducted is to identify the prognostic value and staging categories of magnetic resonance imaging (MRI)–detected intracranial extension in nasopharyngeal carcinoma (NPC) with intensity-modulated radiotherapy (IMRT) to determine whether it is necessary to subclassify the T4 classification NPC. MATERIALS AND METHODS: A total of 335 nonmetastatic T4 classification NPC patients with MRI treated between March 2004 and June 2011 by radical IMRT were included. The T4 classification patients were subclassified into two grades (T4a, without intracranial extension vs. T4b, with intracranial extension) according to the site of invasion. RESULTS: The frequency of intracranial extension was 40.9% (137 of 335 patients). Multivariate analysis identified subclassification (T4a vs. T4b) as an independent prognostic factor for local failure-free survival (p=0.049; hazard ratio [HR], 0.498) and overall survival (p=0.004; HR, 0.572); however, it had no effect on regional failure-free survival or distant failure-free survival (p > 0.050). CONCLUSION: For patients with T4 classification NPC, those with MRI-detected intracranial extension are more likely to experience local failure and death after IMRT than patients without intracranial extension. According to the site of invasion, subclassification of T4 patients as T4a or T4b has prognostic value in NPC.