A case report: Response to Osimertinib in non-small cell lung cancer patient with uncommon EGFR mutation

Abstract

Background: The epidermal growth factor receptor (EGFR) gene harbors a variety of pathogenic variants in non-small cell lung cancer (NSCLC) with several mutations within exons 18–21 serving as common targets for tyrosine kinase inhibitor (TKI) therapy. Osimertinib is a third generation TKI that was initially developed to target the T790M resistance mutation in exon 20 and was found to have additional suppressive action in cells harboring an exon 19 deletion or exon 21 L858R mutation. Case Report: Here we present a case about a patient with NSCLC who was found to have an EGFR amplification with EGFR intron 25 rearrangement identified with FoundationOne® CDx testing who showed a partial response to Osimertinib therapy. Unfortunately, the patient required dose reduction due to persistent side effects resulting in disease progression. Conclusions: Osimertinib has proven to be an effective therapeutic option for patients harboring a variety of EGFR mutations in exons 19–21 by covalently binding to the ATP-binding pocket and overcoming resistance mechanisms that render first and second generation TKI therapies ineffective. In this case, we show that Osimertinib may also provide therapeutic benefit in patients with EGFR intron 25 rearrangements potentially expanding the role of TKI therapy.

Keywords

• EGFR
• Tyrosine kinase inhibitors
• Osimertinib
• Non-small cell lung cancer