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Novel approach for predicting occult lymph node metastasis in peripheral clinical stage I lung adenocarcinoma.

Background
Occult nodal metastasis results in a poor prognosis for lung cancer patients. The aim of this study was to develop an efficient approach for predicting occult nodal metastasis in peripheral clinical stage I lung adenocarcinoma.


Methods
Data for 237 peripheral clinical stage I lung adenocarcinoma patients who underwent complete resection were retrospectively reviewed. Univariate and multivariate analyses were performed to investigate predictors of occult nodal metastasis. Kaplan-Meier analysis was performed for survival.


Results
Occult nodal metastasis was detected in 26/237 (11.0%) patients. Nodule type, tumor SUVmax, whole tumor size, solid tumor size, and preoperative serum carcinoembryonic antigen (CEA) were identified as preoperative predictors of occult nodal metastasis (all P<0.05). Solid tumor size (P<0.001) and preoperative serum CEA (P=0.004) were identified as independent predictors on multivariate analysis. A prediction model was established using the independent predictors. The occult nodal metastasis rate was 2.4% with solid tumor size ≤2.3 cm (low-risk group), 17.0% with solid tumor size >2.3 cm and CEA ≤5 ng/mL (moderate-risk group), and 56.0% with solid tumor size >2.3 cm and CEA >5 ng/mL (high-risk group). The occult nodal metastasis rate was significantly higher in papillary-predominant (11.0%) and solid-predominant subtypes (28.6%; P=0.001). Patients having a micropapillary component had a significantly higher occult nodal metastasis rate (24.2%) compared with no micropapillary component (P=0.007). Histological subtype with micropapillary component and all preoperative predictors were significant prognostic factors affecting disease-free survival (DFS) (all P<0.05).


Conclusions
A novel approach to predict occult nodal metastasis was developed for peripheral clinical stage I lung adenocarcinoma. It would be helpful for selecting candidates for stereotactic ablative radiotherapy (SABR) or wedge resection and mediastinoscopy or endobronchial ultrasound transbronchial needle aspiration (EBUS-TBNA). Complete nodal dissection should be performed for moderate to high-risk patients or patients with poor histologic subtypes.