Haojiang Li^{1}, Chunyan Cui^{1}, Fei Xie^{1}, Jian Zhou^{1}, Annan Dong^{1}, Huali Ma^{1}, and Lizhi Liu^{1}

We aimed to investigate whether the number of metastatic lymph nodes (LNs) is an independent prognostic factor for progression-free survival (PFS) in nasopharyngeal carcinoma (NPC) and to establish a new N staging system based on the number of positive LNs on magnetic resonance imaging. In 792 NPC patients, we found that the number of metastatic LNs was the only independent prognostic factor for PFS following multivariate analysis. We categorized the number of metastatic LNs into 4 groups to create a new N staging system which was more effective than the American Joint Committee on Cancer staging system for predicting PFS.

**INTRODUCTION**

**METHODS**

**RESULTS**

**DISCUSSION**

**CONCLUSION**

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2. Mao YP, Liang SB, Liu LZ, et al. The N staging system in nasopharyngeal carcinoma with radiation therapy oncology group guidelines for lymph node levels based on magnetic resonance imaging. Clin Cancer Res 2008;14(22):7497-503.

3. Heng DM, Wee J, Fong KW, et al. Prognostic factors in 677 patients in Singapore with nondisseminated nasopharyngeal carcinoma. Cancer 1999;86(10):1912-20.

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5. Ho AS, Kim S, Tighiouart M, et al. Association of Quantitative Metastatic Lymph Node Burden With Survival in Hypopharyngeal and Laryngeal Cancer; 2017.

6. Sinha P, Kallogjeri D, Gay H, et al. High metastatic node number, not extracapsular spread or N-classification is a node-related prognosticator in transorally-resected, neck-dissected p16-positive oropharynx cancer. Oral Oncol 2015;51(5):514-20.

Fig 1. Nonlinear relationship
between the number of metastatic LNs
and disease progression risk in training cohort assessed by restricted cubic
spline model.

Fig 2. Kaplan-Meier
estimates for (A) our newly developed and (B) AJCC (8th edition) N classification
systems in the training cohort. Kaplan-Meier estimates for (C) our newly
developed and (D) AJCC (8th edition) N classification systems in the validation
cohort.

Figure S1. The distributions of LN
number in patient groups with different nodal location (A) and laterality (B).
Group
1=retropharyngeal LN without cervical LN; group 2=upper cervical level LN;
group
3=lower cervical level LN; group 4=unilateral cervical LN; group 5=bilateral
cervical LN.

Table 1. Multivariate survival analysis by Cox regression in the training cohort

Abbreviations: LN, lymph node. HR, hazard ratio.

*Multivariable models were adjusted for age, American Joint Committee on Cancer T classification and chemotherapy.

‡Multivariable models were adjusted for age, American Joint Committee on Cancer T classification, chemotherapy and the number of metastatic LNs.