Prognostic value of magnetic resonance imaging-detected cranial nerve invasion in nasopharyngeal carcinoma

BACKGROUND: We previously reported that magnetic resonance imaging evidence of cranial nerve invasion was an unfavourable prognostic factor in nasopharyngeal carcinoma. However, the prognostic value of this evidence in nasopharyngeal carcinoma treated with intensity-modulated radiotherapy remains unknown. METHODS: We retrospectively analysed 749 nasopharyngeal carcinoma patients who underwent intensity-modulated radiotherapy. RESULTS: Cranial nerve invasion was observed in 299 (39.9%) patients with T3–4 disease. In T3–4 nasopharyngeal carcinoma, magnetic resonance imaging-detected cranial nerve invasion was associated with inferior 5-year overall survival, distant metastasis-free survival, and locoregional relapse-free survival (P=0.002, 0.003, and 0.012, respectively). Multivariate analyses confirmed that cranial nerve invasion was an independent prognostic factor for distant metastasis-free survival (hazard ratio, 1.927; P=0.019) and locoregional relapse-free survival (hazard ratio, 2.605; P=0.032). Furthermore, the receiver-operating characteristic curves verified that the predictive validity of T classifications was significantly improved when combined with magnetic resonance imaging-detected cranial nerve invasion in terms of death, distant metastasis, and locoregional recurrence (P=0.015, 0.021 and 0.008, respectively). CONCLUSIONS: Magnetic resonance imaging-detected cranial nerve invasion is an independent adverse prognostic factor in nasopharyngeal carcinoma treated with intensity-modulated radiotherapy.