Abstract: PURPOSE: To investigate the prognostic value of lymph node yield(LNY) and lymph node ratio (LNR) in patients with clinically node-negative (cN0) oral squamous cell carcinoma(OSCC). METHODS: A total of 151 patients diagnosed with cN0 OSCC at the First Affiliated Hospital of the University of Science and Technology of China from January 2008 to January 2018 were included. Based on the presence or absence of lymph node metastasis after surgery, the patients were divided into two groups: pathologic node-negative (pN0) and pathologic node-positive (pN+). The factors influencing lymph node metastasis and the factors affecting recurrence and overall survival in pN0 and pN+ group were analyzed. LNY after neck lymphadenectomy was based on the recommended value of 16 in the literature, and the optimal cutoff value for LNR was calculated using receiver operating characteristic(ROC) curve analysis to classify the patients into two groups. Chi-square test was used for univariate analysis, multivariate analysis for recurrence and overall survival was performed using binary logistic regression and Cox regression models, respectively. Nonparametric Kaplan-Meier survival curves were used to compare the differences in overall survival (OS) and disease-specific survival (DSS). SPSS 26.0 software package was used for data analysis. RESULTS: Among 151 cN0 OSCC patients, totally 109 were pN0(72.2%) and 42 were pN+ (27.8%). The 5-year OS and DSS in pN0 group were significantly higher than those in pN+ group (P<0.05). In the multivariate analysis of recurrence and overall survival in the pN0 group, LNY was an independent risk factor for recurrence(P<0.05), and depth of invasion (DOI) and LNY were independent risk factors for survival(P<0.05). OS and DSS survival curves showed that patients with LNY<16 had significantly lower 5-year survival rates(OS: 65%, DSS: 53%) compared to those with LNY≥16(OS: 80%, DSS: 82%)(P<0.05), allowing for risk stratification of this subgroup of patients. In pN+ group, LNR was identified as an independent risk factor for recurrence and overall survival. Survival analysis of LNR showed that the 5-year survival rate of patients with LNR≤0.075(OS: 80%, DSS: 80%) was significantly higher than that of patients with LNR > 0.075(OS: 25%, DSS: 33%)(P<0.05). CONCLUSIONS: In cN0 OSCC, there are differences in prognosis between pN0 and pN+ patients, and these differences are associated with recurrence and survival. In pN0 group, there are survival differences among patients who experience recurrence. LNY is an independent prognostic factor that affects both recurrence and survival, and a LNY value of ≥16 is associated with a better prognosis compared to LNY<16. In pN+ group, patients who experience recurrence also exhibit survival differences. LNR is an independent prognostic factor for recurrence and survival in these patients, and it allows for risk stratification of this subgroup of patients.

Key words: Oral squamous cell carcinoma, Lymph node yield, Lymph node ratio, Prognosis, TNM staging