Is replacement of the supraclavicular fossa with the lower level classification based on magnetic resonance imaging beneficial in nasopharyngeal carcinoma?

ABSTRACT

PURPOSE AND OBJECTIVES: To investigate the pattern of lymph node metastasis and treatment outcome after intensity-modulated radiotherapy (IMRT) in nasopharyngeal carcinoma (NPC), and assess the possibility of replacing Ho's supraclavicular fossa (SCF) with the lower level (LL; cervical extension below caudal edge of cricoid cartilage) based on magnetic resonance imaging (MRI) as a criterion for N3 disease. METHODS AND MATERIALS We retrospectively reviewed 749 patients with biopsy-proven non-metastatic NPC treated with IMRT. Lymph node metastasis was mapped using the 2013 International Consensus Guidelines. RESULTS: Cervical lymph node (CLN) laterality, CLN greatest dimension (>60 vs. ⩽60 mm) and Ho's SCF were independent prognostic factors for disease-free survival (DFS) and distant metastasis-free survival (DMFS; P<0.01) in multivariate analysis. Replacing Ho's SCF with the LL was also predictive for DFS and DMFS (P<0.01). Compared to the 7th UICC/AJCC, N-categories based on the LL provided more satisfactory distinction between hazard ratios for distant and disease failure for each N-category. N3a and N3b as defined by the 7th UICC/AJCC had similar DMFS (P=0.31) and DFS (P=0.21). CONCLUSIONS: Replacing Ho's SCF with the LL is simple and practical. The N-category staging system could be further simplified by merging N3 subcategories.