Retropharyngeal lymph node metastasis in nasopharyngeal carcinoma detected by magnetic resonance imaging : prognostic value and staging categories.

BACKGROUND: Retropharyngeal lymph node (RLN) metastasis was not included in the current American Joint Committee on Cancer (AJCC) staging system (6th edition) for nasopharyngeal carcinoma (NPC). The object of the current study was to investigate the prognostic value and staging categories of RLN metastasis in NPC detected by magnetic resonance imaging (MRI).
METHODS: All 924 consecutive patients with newly diagnosed NPC were examined with MRI before treatment with definitive intent radiotherapy.
RESULTS: The incidence of RLN metastasis was 73.5%. On multivariate analysis, RLN metastasis was found to be an independent prognostic factor for distant metastasis-free survival (DMFS) in all patients (P = .040). In patients with N0 disease, significant differences were observed between patients with and those without RLN metastasis after adjusting for T classification (P = .046). With regard to laterality, no significant differences were observed in DMFS between patients with unilateral and bilateral RLN metastasis in N0 disease (P = .734). No significant difference in the hazards ratios for either DMFS or disease-free survival (DFS) was found between patients with N0 disease with RLN metastasis and patients with N1 disease (P = .092 and P = .149, respectively). When RLN was classified as N1 disease, there was a better segregation of different N classifications in terms of DFS and DMFS curves, whereas the difference in hazards ratios for N0 and N1 disease was more obvious in DMFS (from 0.461 vs 0.785 to 0.317 vs 0.690).
CONCLUSIONS: The results of the current MRI-based study demonstrate that RLN metastasis affects the DMFS rates of NPC. The authors propose that RLN metastasis be classified as N1 disease, regardless of its laterality.