Uncommon EGFR Mutations in Non-Small Cell Lung Cancer and Their Impact on the Treatment

Background: Epidermal growth factor receptor (EGFR) mutations play an important role in the pathogenesis of non-small cell lung cancer. Because these alterations are so-called targetable mutations, their identification is important in daily clinical practice. The diagnostic standard of EGFR mutations is currently based on polymerase chain reaction methods, particularly the quantitative real-time polymerase chain reaction. In recent years, new generation sequencing has become increasingly important. In patients with EGFR mutations, a significant improvement in therapeutic outcomes was achieved with the administration of targeted therapy using tyrosine kinase inhibitors. EGFR is composed of four domains: extracellular with a ligand binding site, a transmembrane domain, a cytoplasmic tyrosine kinase catalytic domain, and a C-terminal domain. The key structures of the tyrosine kinase domain responsible for signal activation and transmission are encoded within exons 18-21 on chromosome 7. EGFR mutations are highly heterogeneous. About 90% of EGFR mutations are deletions of exon 19 and point mutation L858R in exon 21. These are referred to as classic mutations. Approximately 10% of the total number of EGFR mutations is attributable to less frequent alterations in the EGFR gene. Due to the low incidence of non-small cell lung cancer with less frequent EGFR mutations, information on their predictive significance is still incomplete. Most of the data for the treatment of cases with uncommon mutations were gathered from retrospective analyses and evaluations of small cohorts.

Purpose: The aim of this review is to summarise the current options for diagnosing and treating non-small cell lung cancer patients with uncommon EGFR mutations. This work was supported by the MEYS - NPS I - LO1413 and MH CR - DRO (MMCI, 00209805). The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers. Submitted: 2. 6. 2019 Accepted: 26. 8. 2019.