The IASLC Lung Cancer Staging Project: Recommendation to Introduce Spread Through Air Spaces (STAS) as a Histologic Descriptor in the 9 th Edition of the TNM Classification of Lung Cancer.Analysis of 4,061 Pathologic Stage I Non-Small cell Lung Carcinomas.

Spread through air spaces (STAS) consists of lung cancer tumor cells that are identified beyond the edge of the main tumor in the surrounding alveolar parenchyma. It has been reported by meta-analyses to be an independent prognostic factor in the major histologic types of lung cancer, but its role in lung cancer staging is not established. To assess the clinical importance of STAS in lung cancer staging, we evaluated 4061 surgically resected pathologic Stage I R0 nonsmall cell carcinomas (NSCLC) collected from around the world in the IASLC database. We focused on whether STAS could be a useful additional histologic descriptor to supplement the existing ones of visceral pleural invasion (VPI) and lymphovascular invasion (LVI). STAS was found in 930/4061 of the pathologic stage I NSCLC (22.9%). Patients with tumors exhibiting STAS had a significantly worse recurrence free and overall survival in both univariate and multivariable analyses involving cohorts consisting of all NSCLC, specific histologic types (adenocarcinoma and other NSCLC), and extent of resection (lobar and sublobar). Interestingly, STAS was independent of VPI in all of these analyses. These data support our recommendation to include STAS as a histologic descriptor for the 9th Edition of the TNM Classification of lung cancer. Hopefully gathering this data in the coming years will facilitate a thorough analysis to better understand the relative impact of STAS, LVI and VPI on lung cancer staging for the 10th Edition TNM Stage Classification.