Afatinib for the treatment of advanced non-small-cell lung cancer harboring an epidermal growth factor receptor exon 18 E709_T710delinsD mutation: a case report

BACKGROUND: The discovery of epidermal growth factor receptor oncogenic driver mutations has changed the therapeutic landscape of advanced non-small cell lung cancer in the past decade. Since the introduction of next-generation sequencing, uncommon epidermal growth factor receptor mutations are more frequently discovered. Because seldom evaluated in clinical trials, their clinical significance and response on tyrosine kinase inhibitors are less well known. CASE PRESENTATION: A 58-year-old Caucasian woman with no smoking history presented with advanced non-small cell lung cancer. Liver biopsy revealed an adenocarcinoma with a programmed death ligand-1 tumor proportion score of 30% and no common oncogenic driver mutations. A combination of chemotherapy and immunotherapy was started as first-line treatment. However, treatment was ceased after 18 weeks because of immune-related renal failure and disease progression. In the meantime, the next-generation sequencing results of the liver biopsy had revealed an exon 18 E709_T710delinsD mutation. Therefore, afatinib was administered, which was moderately tolerated with grade 2 paronychia and acneiform skin eruption. After 6 months, a partial response with ongoing decrease of the liver metastasis was retained. CONCLUSION: Because of the lack of clinical trials, tumor heterogeneity, and a tyrosine kinase inhibitor affinity related to the different mutation types, it is difficult to predict the clinical outcome of tyrosine kinase inhibitor in uncommon mutations. Therefore, a therapeutic trial with tyrosine kinase inhibitor has to be considered, but the expected clinical response is lower than for common mutations.