Clinical value of exhaled breath condensate let-7 in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is one of the most common causes of tumor-associated mortality worldwide. Early diagnosis is the key focus for improving prognosis. In the present study, the association between exhaled breath condensate (EBC) let-7 and NSCLC diagnosis and clinicopathologic characteristics was investigated in order to explore non-invasive simple technological therapeutic methods. The expression levels of let-7 from 180 samples were analyzed using the reverse transcription-quantitative polymerase chain reaction (RT-qPCR), consisting of 30 patients with NSCLC (lung cancer and para-carcinoma tissues, serum and EBC) and 30 healthy volunteers (serum and EBC). The results revealed that the let-7 levels in tumor tissues, serum, and EBC in NSCLC were significantly decreased compared with the control group (all, P<0.001). The let-7 expression in lung cancer tissue, serum, and EBC in NSCLC decreased alongside the progression of disease (tumor-node-metastasis stage and lymph node metastasis; all P<0.05). No significant association between let-7 expression and other clinicopathologic characteristics (age, sex, smoking status and histopathologic classification) was identified. A receiver operating characteristic curve (ROC) was used to present data and the area under the curve (AUC) of lung cancer tissue let-7 was 0.894, and the specificity and sensitivity were 90% and 93.3%, respectively. The AUC of serum let-7 in NSCLC diagnosis was 0.771, and the specificity and sensitivity were 86.7% and 60%, respectively. The AUC of let-7 in EBC was 0.750, and the specificity and sensitivity were 76.7% and 66.7%, respectively. In addition, the let-7 expression in EBC was positively correlated with that in lung cancer tissue (r=0.6048, P<0.001) and positively correlated with that in serum (r=0.6454, P<0.001). Taken together, the results of the present study indicated that detection of let-7 was feasible in EBC and with the advantages associated with EBC, and let-7 in EBC may be a promising biomarker for the diagnosis and evaluation of NSCLC.