Prognostic Significance of Metastasis to the Highest Mediastinal Lymph Node in Nonsmall Cell Lung Cancer

Background We have tried to clarify the prognostic significance of metastasis to the highest mediastinal (HM) lymph node in patients with N2 lung cancer who underwent complete dissection of superior mediastinal (including HM) lymph nodes. Methods This study analyzed 53 patients with N2 nonsmall cell lung cancer who underwent surgical procedures such as lobectomy plus hilar and mediastinal node dissection (T4, neoadjuvant therapy cases were excluded). For patients whose cancer was in the left lung, we performed surgery through the median sternotomy in order to dissect superior mediastinal nodes. The clinicopathologic records of the patients were examined for prognostic factors such as age, sex, side, histology, tumor location, tumor size, clinical node (cN) number, preoperative serum carcinoembryonic antigen level, number of metastatic stations, and HM lymph node involvement. Results A univariate analysis showed that tumor size (T1/T2-3), cN factor (cN1-2/cN0), N2 level (multiple/single), and metastasis to the HM node were significant prognostic factors. In the multivariate analysis, metastasis to the HM lymph node remained a significant prognostic factor (p = 0.026). The 3-year survival rates were 52% in patients without metastasis to the HM lymph node and 21% in patients with metastasis to the HM lymph node (p< 0.001). Furthermore, when HM nodal involvement was absent, the 5-year survival rate was 33% even in patients with multilevel N2 status, 45% in patients with cN1-2 status, and 47% in patients with pT2-3 tumor status. Conclusions Highest mediastinal lymph node involvement is prognostic of highly advanced N2 disease resulting in poor outcome. The results also suggest that patients with no involvement of the HM lymph node can experience acceptable postoperative outcomes even if they have multilevel N2 status, positive cN status, or T2-3 tumor status.