Patterns and risk factors of lymph node metastasis in non-small cell lung cancer 2 cm or less.

[BACKGROUND] With the widespread use of computerized tomography (CT) screening, early-stage small-sized (≤2 cm) non-small cell lung cancer (NSCLC) is increasingly detected. However, the optimal extent of lymph node (LN) dissection for these patients remains controversial. This study aimed to comprehensively investigate the patterns and risk factors of LN metastasis in NSCLC ≤2 cm to guide more precise and individualized surgical management.

[METHODS] We conducted a retrospective analysis of 1,878 patients with clinical N0 NSCLC ≤2 cm who underwent surgical resection with adequate LN dissection at our institution between December 2009 and November 2019. Univariate and multivariate logistic regression were used to identify risk factors for LN metastasis.

[RESULTS] The overall LN metastasis rate was 5.6% (106/1,878). Metastasis rates by lobe were: right upper lobe 4.8% (34/712), right middle lobe 5.3% (10/187), right lower lobe 5.6% (17/305), left upper lobe 6.8% (26/384), and left lower lobe 6.6% (19/290). Upper lobe tumors primarily involved upper mediastinal nodes, while lower lobe tumors mainly metastasized to lower mediastinal nodes. Station 7 metastasis occurred in five upper lobe tumors, all measuring ≥1 cm with pure solid appearance. Multivariate analysis identified tumor size ≥1 cm [odds ratio (OR) =64.41, 95% confidence interval (CI): 9.95-877.52], pure solid radiological appearance (OR =7.88, 95% CI: 4.63-14.37), ≥10 LNs removed (OR =1.64, 95% CI: 1.01-2.76), adenosquamous carcinoma (OR =6.02, 95% CI: 2.27-15.76), and pleural invasion (OR =3.66, 95% CI: 2.17-6.11) as independent risk factors. No LN metastasis occurred in tumors <1 cm or pure ground-glass opacity (GGO) nodules.

[CONCLUSIONS] Lobe-specific LN dissection is recommended for NSCLC ≤2 cm. For upper lobe tumors ≥1 cm with pure solid appearance, station 7 dissection should be considered. LN dissection may be omitted for pure GGO nodules or tumors ≤1 cm.