Prognosis And Regulation Of Metastatic Cervical Lymph Nodes Of Nasopharyngeal Carcinoma:Metastasis Distribution Of Posterior To Level V

objective: To retrospectively investigate the regulation of cervical and posterior to level V(PLV)lymph node metastasis on clinical target delineation and update of N stage in radiotherapy for nasopharyngeal carcinoma(NPC).Methods: 428 cases of NPC from December 2011 to April2016 were analyzed and received enhanced CT scan from top of skull to 20 mm inferior of clavicle,all patients were pathologically diagnosed.Chose a deputy chief physician and an attending physician together assessed the nodal distribution in each level according to RTOG guidelines proposed in 2013.The central point of metastatic lymph nodes of PLV in 428 patients were recreated proportionally on the CT images of a standard patient with N0 of NPC with reference to normal anatomy in the area of PLV.Then used the SPSS 20.0 to analyze the nodal distribution of PLV and the correlation between PLV and the other levels,we also analyzed the prognosis of NPC with cervical and PLV lymph node metastasis.Results: Of 428 patients,381(89.0%)had nodal involvement.The top four metastatic probability were as follows: ?b(75.2%),?a(60.3%),?a(59.6%),?(42.0%).The leap metastasis rate was lower than 2.0%.21(4.9%)patients had the nodal involvement of PLV with 32 nodes.The mean vertical distance of all the central points of PLV from the anterior border of trapezius was 16.0 mm(8-37 mm,16.0 ± 9.0).90.6%metastatic nodes of PLV were located in the area that was 25 mm far from theanterior surface of trapezius.Linear-regression analysis indicated the nodal involvement of PLV had correlation with the ipsilateral level Va(P =0.000).The 3 years overall survival,progression-free survival,local relaps-free survival,distant metastasis-free survival of the nodal involvement with PLV were 47.8%,23.5%,80.0%,44.1%,respectively.Multi-factor analysis showed that nodal involvement of PLV was one of the important prognostic factors for distant metastasis-free survival(P =0.000).Conclusions: NPC had a high probability of nodal metastasis.Nodes metastasized mostly from upper to the lower level,and from proximal to the distal area.The leap metastasis rate was very low.The nodal involvement of PLV had correlation with the ipsilateral metastasis of level Va.The ipsilateral delineation of posterior border of level ?should be contoured to 25 mm far from the anterior surface of trapezius when the nodal involvement of level Va.The nodal involvement of PLV indicated more probability in patients with distant metastasis.