Impact of the examined number of lymph nodes at N1 station on the prognosis of patients with pT1-3N0M0 non-small cell lung cancer

Abstract

Objective: To investigate the relationship between the examined number of lymph nodes at the N1 station and the clinicopathological characteristics and prognosis of patients with pT1-3N0M0 non-small cell lung cancer (NSCLC). Methods: A total of 337 patients with pT1-3N0M0 NSCLC who underwent radical lung cancer surgery at the Provincial Hospital Affiliated to Anhui Medical University from January 2013 to March 2015 were selected. The receiver operating characteristic (ROC) curve analysis was used to determine the optimal cut-off value for predicting 5-year survival in pT1-3N0M0 NSCLC patients by the examined number of lymph nodes at the N1 station. The relationships between the examined number of lymph nodes at the N1 station and the clinicopathological characteristics and prognosis of patients with pT1-3N0M0 NSCLC were analyzed according to the optimal cut-off group. Results: A total of 1 321 lymph nodes at N1 station were examined in 337 patients, with a mean of 3.9 nodes per patient. The median survival time was 42.0 months, with 1-, 3- and 5-year survival rates of 82.2%, 57.1% and 24.9%, respectively. ROC curve analysis showed that the optimal cut-off value of 4.5 lymph nodes examined at the N1 station was used to predict 5-year survival in patients with pT1-3N0M0 NSCLC. After rounding off the number, the number of lymph nodes examined at the N1 station was 5 as the cut-off value, and the patients were divided into the group with <5 lymph nodes examined (212 cases) and the group with ≥5 lymph nodes examined (125 cases). The proportion of patients received adjuvant chemotherapy was 19.2% in the group with ≥5 lymph nodes examined, which was higher than 9.0% in the group with <5 lymph nodes examined (P=0.007), and the differences in other clinicopathological characteristics between the two groups were not statistically significant (P>0.05). The median survival time for patients in the group with <5 lymph nodes examined was 38.0 months, with 1-, 3- and 5-year survival rates of 80.1%, 52.5% and 15.6%, respectively. The median survival time for patients in the group with ≥5 lymph nodes examined was 48.0 months, and the 1-, 3- and 5-year survival rates were 85.6%, 64.0% and 36.0%, respectively. The survival rate of patients in the group with ≥5 lymph nodes examined was better than that in the group with <5 lymph nodes examined (P=0.002). Multifactorial Cox regression analysis showed that T stage (OR=1.408, 95% CI: 1.118-1.670) and the examined number of lymph nodes at N1 station (OR=0.670, 95% CI: 0.526-0.853) were independent influence factors for the prognosis of pT1-3N0M0 NSCLC patients. Conclusion: The examined number of lymph nodes at the N1 station is associated with the prognosis of patients with pT1-3N0M0 NSCLC, and the examination of at least 5 lymph nodes at N1 station at the time of postoperative pathological examination improves the 5-year survival rate of patients.