N-staging by magnetic resonance imaging for patients with nasopharyngeal carcinoma: Pattern of nodal involvement by radiological levels

Abstract Background and purpose To study the pattern of lymphatic spread for patients with nasopharyngeal carcinoma (NPC), the significance of retropharyngeal node (RP-LN) involvement, and the possibility of replacing the supraclavicular fossa (SCF) by Levels IV and Vb (LL) as a demarcating criterion for N3-category. Patients and methods The magnetic resonance imagings (MRI) of 202 consecutive patients with NPC treated during 2001–2002 were retrospectively reviewed. Distribution in terms of radiological level (using the same criteria as other head and neck cancers) was mapped, and the size of individual node measured. Prognostic significance of RP-LN and LL was analyzed. Results Only 4% of patients were node-negative on presentation. The nodal involvement occurred predominately at II (94%), III (85%) and RP-LN (80%). The presence of RP-LN affected the N-category in 3.5% of patients, and had no significant impact on tumor control. Replacing SCF by LL as one of the criteria for defining N3 is predictive for both distant control and overall survival. Conclusions With sensitive detection by MRI, the incidence of nodal involvement was very high for patients with NPC. It was difficult to isolate the prognostic significance of RP-LN. The current criterion for defining N3-category by extension into SCF or nodal size >6 cm is the recommended standard, however replacing SCF with LL could be potentially useful and further validation is warranted.