It was a short time from the initial investigation of tumor islands to the concept of tumor spread through air spaces (STAS) being adopted as a pattern of invasion in lung adenocarcinoma. Generally, STAS was defined as "spread of lung cancer cells into air spaces in the lung parenchyma beyond the edge of the main tumor". More and more studies had demonstrated that STAS could increase recurrence rate and cause worse prognosis in lung adenocarcinoma. However, criteria of this definition were various in previous studies, and there is no unified criterion of STAS up to now. In addition, perioperative manipulations including specimen processing and surgery procedure could squeeze tumor cells into alveolar spaces which could affect the assessment of STAS. Obviously, we need a precise definition to reduce and quantify the impacts of confounding factors. We summarize recent developments and put forward some advice for further studies in this article.
ObjectiveTo explore the potential role of tumor spread through air spaces (STAS) as a prognostic indicator of non-small cell lung cancer (NSCLC) through meta-analysis.MethodsPubMed, EMbase and Web of Science, from inception to February 2022 were searched by computer about the research of the 5-year overall survival (OS) and recurrence free survival (RFS) of NSCLC patients with or without STAS. The Newcastle-Ottawa scale (NOS) was used to evaluate the quality of each study.ResultsTotally 13 published articles were included with 4 647 patients, and1 424 (30.6%) patients had STAS. The NOS score of all studies≥6 points. The meta-analysis showed that compared with the NSCLC patients without STAS, those with STAS had a worse prognosis of 5-year RFS, and the combined HR was 1.89 (95%CI 1.61-2.23); they had a shorter 5-year OS, and the combined HR was 2.25 (95%CI 1.79-2.84). There was no statistical heterogeneity among studies.ConclusionThe presence of STAS may be a poor prognostic factor for patients with NSCLC, and enough attention should be paid. The STAS should be recorded in the pathological report to guide the comprehensive treatment and evaluate the prognosis of patients.