Background and objective: With the popularity of minimally invasive techniques, preoperatively determining whether mediastinal lymph node dissection (MLD) is necessary for patients with cN1/2 nonsmall cell lung cancer (NSCLC) has sparked controversy once again. This study aims to analyze whether different primary sites are associated with the distribution of mediastinal lymph node metastases and to investigate the necessity of lymph node dissection and the factors influencing prognosis.
Materials and methods: One hundred and thirteen patients with pathologically confirmed NSCLC with N2 lymph node metastases were included in the study and were grouped according to the lung lobes, in which primary lesions were located for statistically analyzing the metastatic rates of different mediastinal lymph node stations. Through a 3-year follow-up survey, risk factors influencing the 3-year postoperative survival were analyzed.
Results: N2 stations with the highest metastasis rate for different pulmonary lobes were Station 2/4 of the right upper lobe (100%), Station 7 of the right middle/lower lobes (80.0%/88.9%), Station 5 of the left upper lobe (84.4%), and Station 7 of the left lower lobe (78.6%). Three-year survival rate of the cross-regional N2 group was lower than the total N2 group (47.8% vs. 75.3%), P = 0.009 (<0.01). Three-year survival rates for preoperative stages T1 and T2 were superior to stages T3 and T4, showing significant differences (P < 0.05).
Conclusion: Station 7 is likely the most frequently metastases sites in all mediastinal lymph node stations. Cross-regional metastasis of N2 and staging of T3 and T4 were the risk factors for 3-year survival rate, whereas poor differentiation was not the risk factor. Due to the presence of micrometastases and skip metastases, MLD was first recommended for patients with preoperative stage cN1/2.