The ratio of lymph node eluate/serum cytokeratin 21-1 is a potential predictor of lymph node metastasis in lung adenocarcinoma

Lymph node metastasis (LNM) plays an important role in prognosis of lung cancer, either in preoperative TNM staging or postoperative disease recurrence or progress. This study aimed to explore the diagnostic performances of biomarkers from lymph node eluate for LNM in lung adenocarcinoma (LUAD). A prospective analysis was conducted based on lymph node eluate specimens collected via ultrasound-guided lymph node biopsy from 48 LUAD patients with suspected LNM in the neck. According to cytopathological results, the patients were categorized into two groups: one with LNM and the other with non-LNM (NLNM). Carcinoembryonic antigen (CEA), cytokeratin 21-1 fragment (CYFRA21-1), neuron-specific enolase (NSE) and gastrin precursor releasing peptide (ProGRP) in lymph node eluate were detected by immunoassay analyzers, and tumor marker was simultaneously collected in serum of patients. The serum levels of CEA, CYFRA21-1, NSE, and the ratios of CYFRA21-1 and NSE in the lymph node eluate to serum were significantly higher in the LNM group, compared to NLNM group. The areas under curves (AUCs) for CEA, CYFRA21-1, NSE, and ratios of CYFRA21-1 and NSE were 0.79, 0.91, 0.85, 0.93, and 0.89, respectively. The ratio of CYFRA21-1 in lymph node eluate to serum (rCYFRA21-1) performed best in diagnosing, with a sensitivity of 92.3%, a specificity of 92.9%, and an AUC of 0.93. The rCYFRA21-1 to that in the serum might serve as a potential predictor for LNM in LUAD.