Supplementary Material for: EGFR Kinase Domain Duplication in Lung Adenocarcinoma with Response to Osimertinib: A Case Report and Literature Review

Introduction
Liquid and tissue next generation sequencing (NGS) are both important in oncological care. We report a case of metastatic non-small cell lung adenocarcinoma (NSCLC) with a rare Epidermal Growth Factor Receptor kinase domain duplication (EGFR-KDD) identified on liquid biomarker testing which led to sustained targeted treatment.

Case Presentation
A 54-year-old male was diagnosed with metastatic NSCLC and progressed on multiple lines of therapies carboplatin-pemetrexed-pembrolizumab, cisplatin-docetaxel, durvalumab-tremelimumab over a six-month period. Liquid NGS identified a rare EGFR-KDD mutation that was treated with Osimertinib leading to 5 months of progression free survival and significant clinical improvement before ultimately opting for hospice due to intolerance with Osimertinib.

Conclusion
Liquid and tissue NGS should be used in combination to guide treatment and monitor treatment response. Osimertinib may be particularly effective in metastatic NSCLC with EGFR-KDD mutations.