Impact of extended mediastinal lymph node dissection for stage I ground-glass opacity lesions

Background: Mediastinal lymph node dissection (MLND) is a critical component in lung cancer surgery. With the increasing number of patients with ground-glass opacity (GGO) lesions, the clinical impact of MLND has not been sufficiently assessed, particularly for part-solid lesions. This study aimed to evaluate the impact of extended N2 MLND in patients with GGO lesions with a consolidation tumor ratio (CTR) of 0.3-0.7.Methods: Among patients diagnosed with stage I adenocarcinoma between 2013 and 2019, we retrospectively reviewed 138 patients with a CTR of 0.3-0.7. They were divided into the following two groups by MLND: limited N2 MLND (<3 N2 stations; n=100) and extended N2 MLND (>= 3 N2 stations; n=38). Kaplan-Meier curves were used to compare oncologic outcomes and logistic regression was used to identify the predictive factors for postoperative complications (PoCs). Propensity-score matching regarding tumor characteristics and surgical extent were also performed to compare these two MLND assessments in clinical outcome.Results: The extended N2 MLND group had larger solid components (9.5 vs. 7.0 mm, P=0.002) and more patients underwent lobectomy (P=0.008). Kaplan-Meier survival curves revealed no significant difference in clinical outcomes. After propensity score matching, the difference between two MLND strategies was also non-significant in clinical outcome. However, extended N2 MLND was found to be a significant factor in the development of PoC [odds ratio (OR), 4.57; 95% confidence interval (CI): 1.26-16.6; P=0.021]. Conclusions: For GGO lesions with a CTR of 0.3-0.7, the extended MLND strategy may not be optimal in terms of clinical outcome. It could lead to more frequent early complications with no oncologic benefits. Due to the limited number of cases in this study, further prospective research on MLND for part-solid lesions is required.