Background: Lung cancer is the second most common malignancy and is the leading cause of cancer death in the world [1]. Improving cancer diagnostic and treatment methods would help to improve survivability. Currently, both non-small cell and small-cell lung cancer have various types of treatment, including radiotherapy as one of the main treatment options in all stages of lung cancer. Despite of that, thoracic radiotherapy for lung cancer has been linked to an increased risk of cardiac-related morbidity and mortality [2,3]. Currently available methods that predict radiation-induced heart disease (RIHD) are suboptimal. Identifying and developing biomarkers such as circulating plasma microRNAs (miRNAs) could improve the prediction of RIHD. Changes in miRNA expression levels could be a useful, non-invasive liquid biopsy tool for improved risk stratification and precise treatment planning.
The aim of this study was to identify miRNA expression changes in the plasma, taken from Lithuanian lung cancer patients, pre-and post-ionizing radiation treatment, in order to evaluate the effects of treatment on cardiac toxicity.
Methods: 12 pairs of lung cancer patients' plasma samples before and after radiotherapy were included in this study. MiR-1-3p, miR-21-5p, miR-24-3p, miR-29a-3p, miR-34a-5p and miR-222-3p were analyzed. MiRNA expression was examined by reverse transcription quantitative PCR. Results were normalized with exogenous cel-miR-39-3p control and relative expression was calculated.
Results: MiR-1-3p, miR-24-3p, miR-29a-3p, and miR-222-3p were downregulated, while miR-21-5p and miR-34a-5p were upregulated in lung cancer patients' plasma after radiation therapy. Moreover, after treatment, patients with higher natriuretic peptide serum concentration and troponin values showed significant differences in miRNA relative abundance compared to the norm of these indicators.
In conclusion, our study suggests that the identification of microRNA expression level changes in lung cancer patients' plasma before and after radiation therapy could be used for the early detection of RIHD and determine personalized radiation doses to the particular volume of the heart region to reduce toxicity to the heart. However, further analysis is required to validate these miRNAs as potential biomarkers for radiation-induced cardiac toxicity.