Statistical analysis
All statistical analysis was performed using STATA version 14.2. The Kolmogorov-
Smirnov test was used to evaluate the probability distribution of the samples with the reference data. Categorical data were described as median and percentages. A receiver operating characteristic (ROC) curve analysis was performed to identify the nodal volume’s optimal cut-off value with the highest possible sensitivity and specificity. For survival analysis, the Kaplan-Meier method and the log-rank test were used. The Cox proportional hazard model and the univariate and multivariate analysis were performed to evaluate the prognostic factors. Overall survival, disease-free survival, and distant metastasis-free survival were considered to determine the prognostic implications. The p-value of <0.05 was considered statistically significant.