P2.09-27 Prognostic Significance of Vascular Invasion in Pathological Stage IA Lung Adenocarcinoma According to the 8th Edition of the TNM Classification

Abstract

Vascular invasion, including blood vessel invasion (v) and lymphatic vessel invasion (ly), is not a prognostic factor according to the 8th Edition of the Tumor-node-metastasis (TNM) Classification, and the prognostic impact of vascular invasion remains unclear. We reported the prognostic significance of vascular invasion classified according to the previous 7th Edition in patients with stage I non-small cell lung cancer (Diagn Pathol. 2015;10:17). The aim of the present study was to clarify whether vascular invasion classified in the 8th Edition has a prognostic impact on patients with pathological stage IA lung adenocarcinoma and should thus be adopted as an upstaging factor. We reviewed 314 patients with pathological IA (T1a-1bN0 according to the UICC-TNM Classification of Malignant Tumours, 7th Edition) lung adenocarcinoma completely resected between 2000 and 2005. We excluded patients with mucinous adenocarcinoma. The pathological invasive size was measured on the maximal cut surface of the primary tumor, stained with hematoxylin-eosin (HE) and elastica van Gieson (EVG), in all cases. We evaluated blood vessel invasion using specimens stained with HE and EVG, and lymphatic vessel invasion using specimens stained with HE and anti-podoplanin antibody. Blood vessel invasion and lymphatic vessel invasion together represented tumor vessel invasion (TVI). Survival curves were plotted using the Kaplan–Meier method, and the statistical significance of differences between the groups was determined by the log-rank test. The patients were stratified according to the 8th edition into Tis (N = 46), T1mi (N = 69), T1a (N = 82), T1b (N = 99), T1c (N = 18). The median follow-up period was 98.0 months. The recurrence-free survival rate at 5 years was 100%, 100%, 88.9%, 94.7%, 80.3%, 66.7%, and 66.7% in stage 0, IA1(TVI-), IA1(TVI+), IA2(TVI-), IA2(TVI+), IA3(TVI-), and IA3(TVI+), respectively. The lung cancer-specific survival rate at 5 years was 100%, 100%, 88.9%, 98.2%, 87.4%, 66.7%, and 66.7% in stage 0, IA1(TVI-), IA1(TVI+), IA2(TVI-), IA2(TVI+), IA3(TVI-) and IA3(TVI+), respectively. The presence of TVI was a poor prognostic factor in stage IA1 and IA2, but not in stage IA3. TVI is a prognostic factor in patients with lung adenocarcinoma measuring 20 mm or less in the pathological invasive size. Stage IA1 lung adenocarcinoma without TVI can possibly be classified as minimally invasive, because patients with stage IA1 lung adenocarcinoma have 100% recurrence-free survival and lung cancer-specific survival.