Abstract: Objective To analyze the risk factors for level Ib lymph node enlargement on CT in patients with nasopharyngeal
carcinoma (NPC) and provide clinical evidence for defining the indications of prophylactic level Ib irradiation. Methods A
total of 435 newly diagnosed NPC patients receiving radiotherapy in Nanfang Hospital in the past 2 years were enrolled in this
analysis. The correlations were analyzed with Logistic regression between level Ib lymphadenopathy and the clinical risk
factors including T stage, N stage, diameter of level II lymph nodes, submandibular gland involvement, nasal cavity
involvement, oropharyngeal involvement, and involvement of 4 or more lymphatic drainage regions. Results Univariate
analysis showed that level Ib lymphadenopathy were positively correlated with N stage (P=0.023), submandibular gland
involvement (P=0.045), and level II lymph node diameter (P<0.001). Multivariate Logistic regression analysis suggested a
significant correlation only between the diameter of the level II lymph nodes and level Ib lymphadenopathy (P=0.013).
Conclusion Level Ib lymphadenopathy is positively correlated with the size of ipsilateral level II lymph nodes in NPC
patients.