Staging nodal metastases in nasopharyngeal carcinoma: which method should be used to measure nodal dimension on MRI?

AIM: To investigate four methods to measure the maximum dimension (MD) of metastatic neck nodes and correlate with clinical outcome in nasopharyngeal carcinoma (NPC). MATERIALS AND METHODS: Magnetic resonance imaging (MRI) examinations of 712 NPC patients were analysed. MD measurements using methods 1, 2, 3, and 4 were obtained from a single node in the axial plane; a single node in the axial/coronal plane; a single and/or confluent nodes in the axial/coronal plane; and a single and/or confluent and/or contiguous nodes in the axial/coronal plane, respectively. MDs obtained from the four methods were correlated with nodal volume (NV) using Pearson's correlation test. MDs obtained from the four methods, T and N stages, age, gender, and treatment were correlated with overall survival (OS), disease-specific survival (DSS), distant metastases free survival (DMFS), and regional relapse-free survival (RRFS) using cox regression. RESULTS: Method 4 (R: 0.84) had the strongest correlation with NV followed by method 3 (R: 0.77), method 2 (R: 0.70) and method 1(R: 0.69). Method 4 was the only independent nodal measurement of OS, DSS, and DMFS (p-values = 0.008, <0.001 and <0.001, respectively). None of the MD methods was an independent measurement of RRFS. CONCLUSIONS: The best method to obtain the MD for staging incorporates not only single and confluent, but also contiguous metastatic nodes measured in the plane with the MD.