A rare case of Exon 19 deletion transforming to Exon 20 insertion in a case of adenocarcinoma of lung

Epidermal growth factor receptor (EGFR) gene mutations play an important role in the presentation, prognosis, and management of non-small cell lung cancer (NSCLC) patients. Several clinical studies claimed incidence EGFR Exon 20 insertion NSCLC have similar characteristics to those with common but poorer prognosis. Insertion within are typically located after C-helix tyrosine kinase result domain been reported increase activity protein. This eventually leads ligand-independent activation several downstream pathways such as mitogen activated protein (MAPK) phosphatidylinositol-3-kinase (Pi3K)-(mTOR) mammalian target rapamycin pathways, which involved cellular processes proliferation, metastasis, migration while preventing apoptosis. Thus, exon gain function mutations. Specific frame-in insertions occur 3–7% known predict primary resistance treatment all clinically available EGFR-tyrosine inhibitors (TKIs). Many preclinical significant antitumor various first second-generation TKIs Erlotinib, Gefitinib, Afatinib led prolonged survival mutated patients, compared wild-type tumors chemotherapy. In addition, third-generation TKIs, Osimertinib, shown encouraging results metastatic patients harboring including EGFR, p. Thr790Met-mutations, that confer who progressed on prior TKI therapy. Drugs Afatinib, Dacomitinib, Osimertinib already gained FDA approval for use EGFR-mutated Here, we report case a 47-year-old man is non-smoker 19 positive treated Gefitinib developed brain metastasis initiated targeted therapy responded well treatment.