Patterns of lymph node metastases from nasopharyngeal carcinoma: an analysis of 3100 patients based on MRI
2014
Objective To investigate the patterns of lymph node metastases from nasopharyngeal carcinoma (NPC) based on magnetic resonance imaging (MRI) and to provide a basis for neck irradiation field in intensity-modulated radiation therapy.Methods From 2010 to 2013,3 100 patients newly diagnosed with NPC who underwent MRI were analyzed.All images were evaluated by the multi-disciplinary treatment group for NPC to analyze lymph node metastases.The locations of lymph nodes were determined by the RTOG consensus guidelines published in 2003.Results Of 3100 patients,2 679 (86.42%) had lymph node metastases; the detailed distribution was as follows:lateral retropharyngeal region (2012 patients,64.90% ;6 patients were also in the medial group),level Ⅱ b(2341 patients,75.52% ;492 had the upper border reaching half of C1 vertebra and 115 had the upper border reaching the skull base),level Ⅱ a(1798 patients,58.00%),level Ⅲ (1 184 patients,38.19%),level Ⅳ (350 patients,11.29% ;28 had the lower border beyond the RTOG recommended boundary),level Ⅴ (995 patients,32.10% ;91 had the lymph nodes beyond the RTOG recommended boundary),level Ⅰ b (115 patients,3.71%),and parotid region (40 patients,1.29%).Extensive ipsilateral lymph node metastases were seen in patients with lymph nodes metastases in levels Ⅳ and Ⅴ,and the total numbers of involved nodes were ≥ 6 and 7.Skip metastasis occurred in 6 patients (0.19%).Conclusions Metastases to retropharyngeal lymph nodes are seen mainly in the lateral group but rarely in the medial group.The upper border of level Ⅱ lymph nodes should be the skull base.Lymph node metastases from NPC are in an orderly manner,and skip metastasis is rarely seen.When level Ⅳ/Ⅴ lymph nodes are involved,there might exist metastases beyond the RTOG recommended boundary.In case of extensive ipsilateral lymph node metastases,the parotid region might be involved.
Key words:
Nasopharyngeal carcinoma; Magnetic resonance imaging; Lymph node metastasis; Lymph node subregion
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