Spread through air spaces in lung cancer patients is a risk factor for pulmonary metastasis after surgery

Background: Spread through air spaces (STAS) is regarded as a significant risk factor for lung cancer recurrence. STAS consists of micropapillary clusters, solid nests, or single cells beyond the edge of the tumor into air spaces in the surrounding lung parenchyma. However, the patterns of lung cancer recurrence have not been clarified in patients with STAS. The aim of this study was to explore STAS and recurrence patterns in patients who underwent lung cancer surgery. Methods: Between January 2000 and December 2017, a total of 1,426 patients underwent complete resection of lung cancer. We studied 848 patients with pathological stage I disease who underwent surgery. Recurrence patterns and recurrence-free rates were determined from pathological findings, particularly the presence of STAS. Locoregional recurrences included surgical margin recurrences, hilar and mediastinal lymph node metastases, ipsilateral lobe metastases, and pleural dissemination, whereas distant recurrences included extrathoracic organ and contralateral lobe metastases. Results: STAS was observed in 139 of 848 (16.4%) cases. Recurrences developed in 108 (12.7%) cases:locoregional recurrences in 76 (9.0%), distant metastases in 27 (3.2%), and both in 5 (0.6%) cases. Among recurrences, pleural dissemination developed in 12 (1.4%) and pulmonary metastases in 46 (5.4%) cases. Five-year recurrence-free rates were 65.4% among patients with STAS and 89.0% among patients without STAS. Univariate and multivariate analyses revealed that STAS was a significant risk factor for recurrence (P<0.001), particularly locoregional recurrence (P=0.005). In addition, STAS was a significant risk factor for pulmonary metastasis (P=0.009). Conclusions: Among pathological stage I patients who undergo complete resection of lung cancer, patients with STAS tend to develop locoregional recurrence and pulmonary metastases.