Exploratory analysis of spread through air spaces and staple-line recurrence after wedge resection for colorectal lung metastases.

Background: Wedge resection is widely used for pulmonary metastases from colorectal cancer because it preserves lung parenchyma and pulmonary function. However, staple-line recurrence remains an important local control issue. Spread through air spaces (STAS) has been associated with recurrence and poor prognosis in primary lung cancer, but its clinical significance in colorectal lung metastases remains unclear. We explored the association between STAS and staple-line recurrence after initial wedge resection for colorectal lung metastases. Methods: We retrospectively reviewed patients who underwent surgery for pulmonary metastases from colorectal cancer at Osaka Medical and Pharmaceutical University Hospital between January 2011 and December 2020. Patients who underwent wedge resection as the initial surgical procedure for pulmonary lesions were included. The analysis was performed on a lesion basis, including only lesions treated by wedge resection. Variables evaluated for association with staple-line recurrence included STAS status, pathological surgical margin, and tumor/margin ratio. Overall survival (OS) and disease-free survival (DFS) were estimated using the Kaplan-Meier method. Results: Seventy patients with 70 lesions were included. STAS was identified in 17 lesions (24.3%), and staple-line recurrence occurred in 14 lesions (20.0%). On univariable analysis, STAS positivity showed a nonsignificant trend toward an increased risk of staple-line recurrence [odds ratio (OR), 3.07; P=0.08]. In contrast, tumor/margin ratio (OR, 1.38; P=0.049) and pathological surgical margin (OR, 0.15; P=0.03) were significantly associated with staple-line recurrence. In the exploratory multivariable logistic regression model, tumor/margin ratio [OR, 1.52; 95% confidence interval (CI): 1.07-2.15; P=0.02] and STAS (OR, 4.74; 95% CI: 1.20-18.7; P=0.03) remained associated with staple-line recurrence. Model-based prediction showed a higher predicted probability of recurrence in STAS-positive lesions than in STAS-negative lesions at the same tumor/margin ratio. Kaplan-Meier analysis showed nonsignificant trends toward worse DFS and OS in patients with STAS-positive lesions. Conclusions: In this exploratory cohort of initial wedge resections for colorectal lung metastases, staple-line recurrence was associated with tumor/margin ratio, pathological surgical margin, and STAS status. STAS-positive lesions may represent a higher-risk subgroup at a given tumor/margin ratio, although these findings should be interpreted as hypothesis-generating and require validation in larger cohorts.