Circulating Biomarkers in Non-Small-Cell Lung Cancer: Current Status and Future Challenges

Despite recent advances, non-small-cell lung cancer remains a devastating disease and carries a grim prognosis. Major contributing factors include difficulties in diagnosing the disease early in its course during the asymptomatic stage and the poor understanding of the biology underlying disease progression. Liquid biopsies, noninvasive blood tests that detect circulating biomarkers such as circulating tumor cells and tumor-derived nucleic acid fragments, are in a rapidly evolving field of research that could provide answers to both of these unmet needs. Herein, we review the relevant data concerning the diagnostic, predictive, and prognostic significance of 3 distinct but potentially complementary circulating biomarkers in non-small-cell lung cancer: circulating tumor cells, cell-free DNA, and microRNAs.