Effect of tumor size on prognosis of node-negative lung cancer with sufficient lymph node examination and no disease extension

BACKGROUND: The effect of tumor size on the prognosis of node-negative non-small-cell lung cancer (NSCLC) might be biased by missed lymph node metastasis and local disease extension. METHODS: We investigated 2,260 patients with N0M0 NSCLC in the Surveillance, Epidemiology and End Results (SEER) database diagnosed from 1998 to 2012. Eligible patients had $18 lymph nodes examined and no disease extension. Tumor size was classified as T1a (0–10 mm), T1b (11–20 mm), T1c (21–30 mm), T2a (31–40 mm), T2b (41–50 mm), T3 (51–70 mm), and T4 (>70 mm). RESULTS: The 5-year cancer-specific survival (CSS) rates for T1a, T1b, T1c, T2a, T2b, T3, and T4 patients were 85.6%, 84.4%, 79.9%, 77.9%, 70.0%, 63.0%, and 61.7%, respectively. The 5-year overall survival (OS) rates for T1a, T1b, T1c, T2a, T2b, T3, and T4 patients were 77.8%, 74.1%, 68.2%, 64.5%, 58.7%, 53.2%, and 57.3%, respectively. Using T1a as the reference, the hazard ratio generally increased with tumor size in the multivariate analysis of CSS and OS, with the exception of T4 patients. CONCLUSION: After adjusting for lymph node examination and disease extension, tumor size still had a significant effect on CSS in NSCLC, although the effect seemed to be smaller than that in a more generalized population.