EGFR-tyrosine kinase inhibitor treatment in a patient with advanced non-small cell lung cancer and concurrent exon 19 and 21 EGFR mutations: A case report and review of the literature.

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are considered to be effective treatments for advanced non-small cell lung cancer (NSCLC) patients with sensitizing EGFR mutations, including exon 19 deletion and exon 21 L858R mutations. However, with the development of EGFR mutation detection assays, patients with complex EGFR mutations are emerging, and their response to EGFR-TKIs remains unclear. The present study reports a case of a 62-year-old, non-smoking female patient with advanced NSCLC, presenting with concurrent EGFR 19+21 sensitizing mutations, who had a poor response to the first-line EGFR-TKI erlotinib and succumbed 5 months subsequent to diagnosis. Furthermore, the present study performed a literature review, and 18 patients with complex EGFR 19+21 mutations that had received EGFR-TKIs were identified. The majority of these patients responded well to EGFR-TKIs. To the best of our knowledge, the present case is the first to report a patient with lung adenocarcinoma with complex EGFR 19+21 sensitizing mutations that had a poor clinical response to a first-line EGFR-TKI. Despite the 70% response rate of sensitizing EGFR-mutant NSCLCs to EGFR-TKIs, there is still a proportion of patients that experience de novo resistance, and heterogeneity is likely to be important in this resistance mechanism. Therefore, comprehensive genomic detection assays and multi-targeted therapies for patients with NSCLC with complex EGFR mutations require additional investigation.