Grading of MRI-detected skull-base invasion in nasopharyngeal carcinoma and its prognostic value.

BACKGROUND Our aim was to grade MRI-detected skull-base invasion in nasopharyngeal carcinoma and evaluate the prognostic value of the grading. METHODS The MRI scans and medical records of 924 patients with histologically diagnosed nondisseminated nasopharyngeal carcinoma were reviewed retrospectively. RESULTS MRI-detected skull-base invasion was not found to be an independent prognostic factor for overall survival, distant metastasis-free survival, or local relapse-free survival (p > .05 for all). Grading of skull-base erosion according to the site of invasion was found to be an independent prognostic factor for both overall survival (p = .003 and p = .006, respectively) and distant metastasis-free survival (p = .001 for both) in the 512 patients with skull-base invasions and 315 patients with T3 disease. CONCLUSIONS MRI-detected skull-base invasion is not an independent prognostic factor for nasopharyngeal carcinoma. However, grading according to the site of invasion as either low grade or severe has prognostic value.