EGFR exon 20 mutation is one of many mutations that have been identified as drivers of cancer growth in non-small cell lung cancer (NSCLC). Mutations in the EGFR, or epidermal growth factor receptor, have been described in the tumor tissue of NSCLC, and patients whose tumors harbor these mutations have had successful responses to certain targeted drugs that inhibit the activity of the EGFR. Unlike more common mutations in the EGFR, tumors that arise with an exon 20 mutation are not sensitive to the EGFR inhibitor drugs used to treat patients with other types of EGFR alterations. This has led to research and development of specific drugs that are active in tumors containing this specific genetic change.
Vyse, Simon, and Paul H. Huang. "Targeting EGFR exon 20 insertion mutations in non-small cell lung cancer." Sig Transduct Target Ther 4.5 (2019). <https://www.nature.com/articles/s41392-019-0038-9>.