**6. Therapeutic approach**

Targeted drug therapy is recommended for the treatment of lung cancers. It is primarily used to treat non-small-cell lung cancers that constitute 80–85% of lung cancers. It targets the abnormalities in tumor cells without damaging the healthy cells. Biomarker testing is emerging as a tool in targeted therapy for testing patients who have abnormalities in their DNAs, which can be detected after looking for changes in the tumor cells. These changes can be additions, deletions, point mutations, rearrangements, or genetic alterations in the DNA. These changes are targeted in most lung cancer treatments. Targeted therapy is often associated with fewer side effects as they focus on the specific target that is mutated in the cell. These drugs target the pathways involved in lung adenocarcinomas. A number of pathways have been implicated in the causation of lung cancer such as EGFR, PI3K/ AKT/mTOR, NTRK/ROS1, and RAS–MAPK, which have been targeted for the treatment purpose. Targeted therapy drugs have now replaced chemotherapy as the first-line treatment, such as EGFR inhibitors erlotinib, gefitinib, PI3K/AKT/mTOR inhibitors everolimus, and NTRK/ROS1 inhibitors entrectinib. These drugs have been found to be clinically beneficial and safer than conventional chemotherapy in the treatment of lung cancer [74, 75].
