T1aN0M0 and T1bN0M0 Non–Small Cell Lung Cancer: A Retrospective Study of the Prognosis

Abstract

Stage IA of non-small cell lung cancer (NSCLC) is divided into two subgroups, T1aN0M0 (d ≤ 2 cm) and T1bN0M0 (2 < d ≤ 3 cm), in the International Association for the Study of Lung Cancer, seventh edition of TNM Classification of Malignant Tumors. The purpose of this study was the identification of independent clinicopathological predictors of prognosis of these two subgroups of NSCLC. Between 1986 and 2005, a cohort of 1,929 cases of stage IA NSCLC in Tian Jin Medical University Cancer Institute and Hospital were retrospectively analyzed. The impact of clinicopathological characteristics on patients' survival was investigated. The overall 5-year survival rate was 71.07%. Patients with T1aN0M0 NSCLC had a better 5-year survival than those with T1bN0M0 (73.98 vs. 68.18%, p = 0.0135). The Cox proportional hazard model revealed that the prognostic factors of T1aN0M0 were intratumoral vessel invasion (p = 0.035) and histologic differentiation (p = 0.004). In patients with T1bN0M0 NSCLC, the prognostic factors were histologic differentiation (p < 0.01), intratumoral vessel invasion (p < 0.01), removal of 6 or more lymph node stations (p < 0.01), and removal of lymph node station 7 (p < 0.01). Prognostic factors of T1aN0M0 and T1bN0M0 NSCLC are different. In patients with T1bN0M0 NSCLC, 6 or more lymph node stations and lymph node station 7 should be removed.