Caudal distribution pattern of metastatic neck lymph nodes in nasopharyngeal carcinoma and prognostic significance of nodal spread distances

To investigate the caudal distribution pattern of metastatic neck lymph nodes (LNs) in nasopharyngeal carcinoma (NPC) and the prognostic significance of nodal spread distances (SDs).NPC patients with neck metastatic LNs were enrolled. The most caudally located LNs were marked. SD was defined as the distance from marked LNs to the lateral process of the atlantoaxial spine (LPC1). Univariate and multivariate analyses were performed to assess association between MRI-identified nodal features and survival. Harrell's concordance index (C-index) and area under the curve (AUC) were used to compare AJCC (8th edition) N staging with the proposed N staging. Survival after induction chemotherapy plus concurrent chemoradiotherapy (IC + CCRT) versus CCRT alone was compared between different SD groups.A total of 1907 LNs (1164 patients) were contoured. SD > 7 cm was an independent predictor of overall survival (OS), distant metastasis-free survival (DMFS), and progression-free survival (PFS), with hazard ratios of 1.725, 1.553 and 1.414, respectively. When patients with SD > 7 cm were upgraded one N stage higher, the proposed N classification showed better stratification in OS, DMFS, and PFS between N1 and N2 stages. C-indices and AUCs of the proposed N staging were superior to AJCC N staging. IC + CCRT showed negative effect in N1-2 patients with SD ≤ 7 cm but improved OS in those with SD > 7 cm.SD of metastatic LNs can predict survival in NPC. Integration of SD into AJCC N staging could improve its prognostic value and help identify patients requiring IC.