Abstract:ObjectiveBased on the published articles, this paper aims to study the pattern and probability of lymph nodes metastasis in nasopharyngeal carcinoma (NPC) and establish a radiotherapy standard for selecting and delineation of clinical target volume of neck lymphatics for NPC patients with N0 or N1.MethodsClinical trials about NPC by MRI as the main or only diagnostic imaging way were collected and extracted from database, such as WanFang, CBM, PubMed, Cochrane Library. Statistical analyses were performed using Stata software, version 12.0. ResultsTwentyone clinical trials from 963 original articles were included in this analysis. The most commonly involved regions included retropharyngeal (67%) and level Ⅱ lymph nodes (71%). The overall probability of levels Ⅲ, Ⅳ and Ⅴnodal involvement were 37%, 14% and 21%, respectively. Lowrisk node groups included levels ⅠA, ⅠB, Ⅵ nodes, and the rates of lymph node metastasis were 0, 2%, 2% and 1%, respectively. Nodal metastases followed an orderly pattern of topdown, and the probability of "skip" metastasis between levels varied between 0.5%～7.9%. ConclusionLymph node metastasis in NPC follows a predictable and orderly pattern. The rarity of metastasis in certain nodal groups and "skip" metastasis suggest that reduced treatment volume is feasible in conformal radiotherapy for NPC patients with N0 or N1.

Key words:Nasopharyngeal neoplasms,Lymphatic metastasis,Meta-analysis