Background: Mutations in the epidermal growth factor receptor gene (EGFR) are found in around half of Asian patients with non-small cell lung cancer (NSCLC). For this reason, EGFR tyrosine kinase inhibitors (TKI) are often prescribed depending on the EGFR status. Two common EGFR mutations, a deletion in exon 19 and L858R in exon 21, demonstrate a positive response to gefitinib, the first approved EGFR TKI. However, T790M and an insertion in EGFR exon 21 are resistant to EGFR TKI treatment. The relationships between the EGFR mutation type and response to the target drug have not been fully investigated.
Case presentation: We describe a 66-year-old Chinese male diagnosed with stage IV lung adenocarcinoma based on evidence from a computed tomography (CT) scan and histological features of a biopsy taken during fiberoptic bronchoscopy surgery. Molecular analysis of EGFR exons 19 and 21 revealed the presence of only one mutation in exon 19: L747P (2239-2240 TT>CC). The patient requested gefitinib treatment for 2 weeks but his response was poor. A CT scan revealed that the number and relative volume of the liver metastases had increased after treatment.
Conclusion: L747P (2239-2240 TT>CC) in exon 19 is a rare EGFR mutation that appears to lead to gefitinib resistance and might accelerate liver metastases.
Keywords: EGFR; L747P; drug resistance; gefitinib; liver metastases.