BACKGROUND: Mediastinal staging is of paramount importance for planning of treatment in non-small cell lung cancer (NSCLC). Single institution reports recently claimed that subcarinal lymph node dissection during resection of upper lobe NSCLC could be spared. We used a complete national lung cancer registry to investigate patterns of unsuspected mediastinal lymph node involvement after lobectomy.
METHODS: During an 11-year period (2004 to 2014) 5,577 consecutive patients who underwent operations for NSCLC were investigated for unsuspected mediastinal lymph node involvement (N2 disease) discovered at final histopathology. The analysis excluded patients with clinical N2 disease. We used a national registry to extract information for each patient about tumor location, histopathology, clinical and pathologic TNM stage, preoperative imaging modalities, and type of invasive mediastinal staging.
RESULTS: Mediastinal lymph node dissection was performed in 5,577 patients during the operation, and unsuspected N2 disease was discovered in 612 (11.0%), and 193 (3.5%) had subcarinal metastasis. Subcarinal N2 disease was significantly more common in patients with lower-lobe or middle-lobe cancers compared with upper-lobe cancers (5.8% vs 1.6%, p < 0.01). Preoperative invasive mediastinal staging was performed in 73.4% (4,097 of 5,577) of all patients and significantly more frequently in patients who eventually had N2 disease (87.3% [534 of 612], p < 0.01) as well subcarinal N2 disease (89.6% [173 of 193], p < 0.01).
CONCLUSIONS: Subcarinal lymph node metastases were common despite frequent use of preoperative invasive mediastinal staging in lower-lobe, middle-lobe, and upper-lobe NSCLC. Subcarinal lymph nodes should be dissected or sampled routinely during operations for NSCLC to avoid understaging-regardless of preoperative invasive mediastinal staging and tumor location.