The Impact of Superior Mediastinal Lymph Node Metastases on Prognosis in Non-small Cell Lung Cancer Located in the Right Middle Lobe

Abstract

We aimed to assess hilar and mediastinal lymph node involvement and its impact on prognosis in patients with right middle lobe lung cancer. The records of 170 patients undergoing surgery for right middle lobe non-small cell lung cancer from 1980 to December 2007 were retrospectively examined. There were 45 patients found to have hilar or mediastinal lymph nodes metastases. This subgroup included 31 N2 patients and 14 N1 patients, and included 23 women and 22 men, whose ages ranged from 32 to 83 years (median = 61 years). The status of mediastinal, hilar, and interlobar lymph nodes was assessed according to the seventh edition of the TNM classification for lung cancer. Patient records were examined for age, gender, preoperative nodal status, surgical procedure, metastatic status of lymph nodes (distribution and numbers), tumor size, and histologic features (cell type and differentiation degree). Survival duration was defined as the interval between surgery and death from the tumor or the most recent follow-up. For N1 cases (n = 14), the most frequent metastatic site was #12m (lymph nodes adjacent to the middle lobe bronchus), which occurred in 11 cases; there was one case with metastases in #11s (lymph nodes between the upper lobe bronchus and bronchus intermedius), and no case with #11i metastases (lymph nodes between the right middle and lower lobe bronchi). The most frequent metastatic mediastinal zone was the subcarinal zone (25/31), and the superior mediastinal zone also had a high incidence of metastases (22/31). Sixteen cases had metastases to both the superior and subcarinal zones, and six cases had metastasis to superior mediastinal zone without subcarinal zone metastasis. When #11s or #11i was involved, eight of nine or five of five, respectively, were N2 cases. Univariate analyses revealed that tumor diameter, cN, status of lymph node metastases, and operative procedure (pneumonectomy) were significant prognostic factors in N2 cases. Regarding status of lymph node metastases, superior mediastinal zone metastases, both superior and inferior (subcarinal) zone metastases, and #11i were significant prognostic factors. Because #11i metastases and superior mediastinal lymph nodes metastases were highly correlated with each other (p = 0.02), two separate models were used in multivariate analyses. Superior mediastinal metastases (p = 0.03) and #11i metastases (p = 0.015) were revealed to be significant independent prognostic factors, whereas multiple-zone metastases only tended toward significance as an adverse prognostic factor (p = 0.054). Superior mediastinal lymph node metastases and #11i metastases were significant adverse prognostic factors in patients with middle lobe lung cancer, and they were associated with each other.