Semiquantitative Assessment of Tumor Spread through Air Spaces (STAS) in Early-Stage Lung Adenocarcinomas

Abstract

IntroductionTumor spread through air spaces (STAS) has recently been reported as a form of tumor invasion having an unfavorable prognosis, but the significance of a small amount of STAS is not known. The aim of this study was to perform a semiquantitative assessment of STAS. MethodsSmall (≤2 cm) stage I lung adenocarcinomas surgically resected at our institution between 2003 and 2009 were assessed semiquantitatively in the most prominent area as no STAS, low STAS (1–4 single cells or clusters of STAS), or high STAS (≥5 single cells or clusters of STAS) by using a 20× objective and a 10× ocular lens. A statistical analysis was performed to determine the impact of clinicopathologic parameters on STAS and to clarify the relationship between STAS and patient survival. ResultsSTAS was assessed as no STAS in 109 of 208 cases (52.4%), as low STAS in 38 cases (18.3%), and as high STAS in 61 cases (29.3%). There were statistically significant associations between higher STAS and solid predominant invasive adenocarcinoma (p < 0.001), pleural invasion (p < 0.001), lymphatic invasion (p < 0.001), vascular invasion (p < 0.001), and tumor size of 10 mm or more (p = 0.037). There was a significant association between increasing STAS and shorter recurrence-free survival (RFS) in univariate analysis (no STAS, 154.2 months; low STAS, 147.6 months; and high STAS, 115.6 months). In a multivariate Cox proportional hazards model, only STAS (p = 0.015) remained a significant predictor of RFS. ConclusionsWe found that one-third of resected small adenocarcinomas had high STAS. Higher STAS was predictive of worse RFS.