Re-evaluating the need for mediastinal lymph node dissection and exploring lncRNAs as biomarkers of N2 metastasis in T1 lung adenocarcinoma

BACKGROUND: Although a well-acknowledged component of curative surgery for lung cancer, investigators have recently questioned the need for mediastinal lymph node dissection (MLND) in early-stage lung cancer cases. As such, the accurate prediction of N2 stage prior to surgery has become increasingly critical. But diagnostic biomarkers predicting N2 metastases are deficient, which are urgently needed. METHODS: We extracted the data of non-small cell lung cancer (NSCLC) patients whose clinical information and follow-up data are complete and without preoperative induction therapy from the Surveillance, Epidemiology, and End Results (SEER) database. The SEER program registries routinely collect demographic and clinic data on patients. And the prognostic differences were analyzed according to the presence or absence of MLND in their lung resection using the R package. Subsequently, the correlations between pN2 metastasis and clinical characteristics were analyzed. In parallel, the long non-coding RNAs (lncRNAs) associated with pN2 status were screened in The Cancer Genome Atlas (TCGA) database by expression difference analysis between pN0-N1 and pN2 patients using limma. Their diagnostic efficiency for detecting N2 metastases was evaluated using receiver operating characteristic (ROC) curves, and a combined diagnostic model was constructed using logistic regression and ROC curve analyses in lung adenocarcinoma (LUAD). RESULTS: There were 16,772 patients in MLND group, and 2,699 cases in no-MLND group. The clinical data from SEER showed that the incidence of N2 metastasis was low in pT1 NSCLC (1,023/16,772, 6.10%), but the prognosis of no-MLND patients was poorer than those who underwent MLND (P<0.001, HR =1.605). Pathological N2 metastasis was correlated with age, histologic type, and tumor size. On the other hand, five lncRNAs (LINC00892, AC099522.2, LINC01481, SCAMP1-AS1, and AC004812.2) were screened and confirmed as potential diagnostic biomarkers for detecting N2 metastasis in pT1 LUAD. The AUC of the combined indicators was 0.857. CONCLUSIONS: MLND may be oncologically necessary for selected T1 NSCLC patients based on the metastasis incidence and prognosis. A diagnostic model combining LINC00892, AC099522.2, LINC01481, SCAMP1-AS1, and AC004812.2 expression levels may have the potential to be a diagnostic biomarker for detecting N2 metastasis in pT1 LUAD. This study suggests that MLND might be omitted in patients with lower expression level of this diagnostic model.