Impact of the distance of spread through air spaces in non-small cell lung cancer.

Objectives: Spread through air spaces (STAS) is considered a poor prognostic factor in patients with resected non-small lung cell cancer; however, the clinical significance of STAS extent remains unclear. We hypothesized that the further the tumour cells spread from the tumour edge, the worse the prognosis becomes.

Methods: This study retrospectively reviewed the data of 642 patients with completely resected pathological stage I-III non-small lung cell cancer between 2008 and 2018. The maximum spread distance (MSD) from the tumour edge to the farthest STAS was quantitatively evaluated, and STAS was categorized as limited (MSD ≤1000 μm) or extended (MSD >1000 μm), based on the median MSD. Recurrence-free survival (RFS) and overall survival (OS) were compared among patients stratified by STAS classification.

Results: Patients were classified into STAS-negative (n = 382, 59.6%), limited STAS (n = 130, 20.2%) and extended STAS (n = 130, 20.2%) groups. Extended STAS was associated with a high maximum standardized uptake value, advanced pathological stage and vascular invasion compared with limited STAS. The extended STAS group demonstrated significantly shorter RFS and OS than both the limited STAS and STAS-negative groups (both P < 0.001 for RFS; P = 0.007 and P < 0.001 for OS, respectively). Multivariable analysis showed that extended STAS was an independent prognostic factor for both RFS and OS (P < 0.001, P < 0.001, respectively).

Conclusions: The distance from tumour edge to STAS affects prognosis in patients with completely resected non-small lung cell cancer.

Clinical registration number: IRB approval number: 2019-232.