Durable response to EGFR tyrosine kinase inhibitors in a patient with non-small cell lung cancer harboring an EGFR kinase domain duplication.

Epidermal growth factor receptor (EGFR) kinase domain duplication (KDD) has been identified as an oncogenic driver in 0.05% to 0.14% of non-small cell lung cancer (NSCLC) patients. However, little is known of the efficacy of EGFR tyrosine kinase inhibitors (TKIs) for such patients. Here, we report the case of a 45-year-old Japanese woman with NSCLC positive for EGFR-KDD (duplication of exons 18-25) who developed carcinomatous meningitis and showed a marked response to the EGFR-TKIs erlotinib and osimertinib. As far as we are aware, this is the first report of EGFR-TKI efficacy for carcinomatous meningitis in a NSCLC patient harboring EGFR-KDD.