Objective: To determine the extent of lymph node metastasis in clinical stage I non-small-cell lung cancer (NSCLC).
Methods: We performed a retrospective review of 524 patients with clinical stage I NSCLC who underwent lobectomy with systematic nodal dissection.
Results: The nodal status was N0 in 409 patients (78%), N1 in 44 (8%), N2 in 67 (13%), and N3 in four (0.8%). Thirty-six patients had single-level mediastinal nodal metastases and 35 had multi-level metastases. The incidence of N2/3 disease in patients with adenocarcinoma/squamous cell carcinoma/other histologic types according to tumor size was 0/0/0%, respectively, in tumors < or = 10 mm in diameter, 12/0/0% in tumors 11-20 mm in diameter, 14/4/23% in tumors 21-30 mm in diameter, and 26/14/20% in tumors >30 mm in diameter. Nodal metastases to the upper mediastinum from middle or lower lobe lesions were frequently observed in 51 N2 adenocarcinomas, whereas those to the lower mediastinum from upper lobe lesions were rare. Of 10 N2 squamous cell carcinomas, seven had regional and three had non-regional nodal metastases. The 5-year survival rate was 68, 43, and 30% in N0, N1, and N2, respectively (P<0.01, N0 versus N1, N0 and N2).
Conclusions: Systematic mediastinal nodal dissection should be routinely performed for clinical stage I lung cancer to ensure the correct nodal status, but it might be dispensable in the patients with peripheral squamous cell carcinoma < or = 20 mm in diameter, with central squamous cell carcinoma < or = 30 mm, and with adenocarcinoma < or = 10 mm. When systematic nodal dissection cannot be performed, the incidence and extent of nodal metastases should be taken account with respect to histologic type, size, and location of the tumor.