Applications of liquid biopsy in lung cancer-diagnosis, prognosis prediction, and disease monitoring

Lung cancer is the most common cancer in both the developing and developed countries, which has an unoptimistic outcome. As a result of high rates in mortality and considerable difficulties in treatment, early detection of lung cancer is thought as one of the potential solutions for this stigma. Tissue biopsy has been widely used for cancer diagnosis, but the invasive nature limits their application, especially when repeated biopsies are needed. Liquid biopsy, a minimally invasive procedure aiming to primarily analyze circulating tumor cells (CTCs) and/or circulating tumor DNA (ctDNA) for diagnosing and profiling cancer, has gained interest from oncologists and basic researchers. A great number of achievements in the field of liquid biopsy has been developed, thus liquid biopsy is more feasible in clinical practice than before. More importantly, liquid biopsy is being used, in addition to the diagnosis of lung cancer, to predict prognosis according to genetic alterations and monitor disease based on signature molecular markers. In this review, we briefly summarize techniques in liquid biopsy and focus on its applications in disease diagnosis, prognosis prediction, and condition monitoring of lung cancer.