Liquid biopsy in lung cancer.

In the era of the personalized medicine, we need not only to an accurate diagnosis of lung cancer but also to assess the molecular pathways involved in order to target them. The most relevant targets in lung cancer are the genes EGFR, ALK-EML4, ROS1, Her2Neu, BRAF. Mutations or translocations of these genes are performed on biopsies in 80% of the cases and 30% of the patients cannot have their molecular tests done. This may be due to the lack of tumor samples secondary to the morphologic and immunohistochemical techniques, contraindication to biopsy or difficulties to biopsy. Besides, tumor cells tend to activate other pathways that weren't activated at the onset in order to escape to therapeutic drugs. This phenomenon of resistance is observed 3 to 6 months after the onset of the treatment. In order to escape all these limitations, liquid biopsy was developed. It consists in a simple blood sample of 5 to 10 ml in which circulating tumor cells, circulating tumor DNA, tumor RNA, exosomes and secretomes are explored. In this paper, we tried to define liquid biopsy, to highlight the means of diagnosis, its limits, its advantages and its perspectives in Tunisia.